/* * Generic ring buffer * * Copyright (C) 2008 Steven Rostedt */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "trace.h" /* * The ring buffer is made up of a list of pages. A separate list of pages is * allocated for each CPU. A writer may only write to a buffer that is * associated with the CPU it is currently executing on. A reader may read * from any per cpu buffer. * * The reader is special. For each per cpu buffer, the reader has its own * reader page. When a reader has read the entire reader page, this reader * page is swapped with another page in the ring buffer. * * Now, as long as the writer is off the reader page, the reader can do what * ever it wants with that page. The writer will never write to that page * again (as long as it is out of the ring buffer). * * Here's some silly ASCII art. * * +------+ * |reader| RING BUFFER * |page | * +------+ +---+ +---+ +---+ * | |-->| |-->| | * +---+ +---+ +---+ * ^ | * | | * +---------------+ * * * +------+ * |reader| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * | |-->| |-->| | * +---+ +---+ +---+ * ^ | * | | * +---------------+ * * * +------+ * |reader| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * ^ | |-->| |-->| | * | +---+ +---+ +---+ * | | * | | * +------------------------------+ * * * +------+ * |buffer| RING BUFFER * |page |------------------v * +------+ +---+ +---+ +---+ * ^ | | | |-->| | * | New +---+ +---+ +---+ * | Reader------^ | * | page | * +------------------------------+ * * * After we make this swap, the reader can hand this page off to the splice * code and be done with it. It can even allocate a new page if it needs to * and swap that into the ring buffer. * * We will be using cmpxchg soon to make all this lockless. * */ /* * A fast way to enable or disable all ring buffers is to * call tracing_on or tracing_off. Turning off the ring buffers * prevents all ring buffers from being recorded to. * Turning this switch on, makes it OK to write to the * ring buffer, if the ring buffer is enabled itself. * * There's three layers that must be on in order to write * to the ring buffer. * * 1) This global flag must be set. * 2) The ring buffer must be enabled for recording. * 3) The per cpu buffer must be enabled for recording. * * In case of an anomaly, this global flag has a bit set that * will permantly disable all ring buffers. */ /* * Global flag to disable all recording to ring buffers * This has two bits: ON, DISABLED * * ON DISABLED * ---- ---------- * 0 0 : ring buffers are off * 1 0 : ring buffers are on * X 1 : ring buffers are permanently disabled */ enum { RB_BUFFERS_ON_BIT = 0, RB_BUFFERS_DISABLED_BIT = 1, }; enum { RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT, RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT, }; static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON; #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) /** * tracing_on - enable all tracing buffers * * This function enables all tracing buffers that may have been * disabled with tracing_off. */ void tracing_on(void) { set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); } EXPORT_SYMBOL_GPL(tracing_on); /** * tracing_off - turn off all tracing buffers * * This function stops all tracing buffers from recording data. * It does not disable any overhead the tracers themselves may * be causing. This function simply causes all recording to * the ring buffers to fail. */ void tracing_off(void) { clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags); } EXPORT_SYMBOL_GPL(tracing_off); /** * tracing_off_permanent - permanently disable ring buffers * * This function, once called, will disable all ring buffers * permanently. */ void tracing_off_permanent(void) { set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags); } /** * tracing_is_on - show state of ring buffers enabled */ int tracing_is_on(void) { return ring_buffer_flags == RB_BUFFERS_ON; } EXPORT_SYMBOL_GPL(tracing_is_on); #include "trace.h" #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) #define RB_ALIGNMENT 4U #define RB_MAX_SMALL_DATA 28 enum { RB_LEN_TIME_EXTEND = 8, RB_LEN_TIME_STAMP = 16, }; /* inline for ring buffer fast paths */ static unsigned rb_event_length(struct ring_buffer_event *event) { unsigned length; switch (event->type) { case RINGBUF_TYPE_PADDING: /* undefined */ return -1; case RINGBUF_TYPE_TIME_EXTEND: return RB_LEN_TIME_EXTEND; case RINGBUF_TYPE_TIME_STAMP: return RB_LEN_TIME_STAMP; case RINGBUF_TYPE_DATA: if (event->len) length = event->len * RB_ALIGNMENT; else length = event->array[0]; return length + RB_EVNT_HDR_SIZE; default: BUG(); } /* not hit */ return 0; } /** * ring_buffer_event_length - return the length of the event * @event: the event to get the length of */ unsigned ring_buffer_event_length(struct ring_buffer_event *event) { unsigned length = rb_event_length(event); if (event->type != RINGBUF_TYPE_DATA) return length; length -= RB_EVNT_HDR_SIZE; if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) length -= sizeof(event->array[0]); return length; } EXPORT_SYMBOL_GPL(ring_buffer_event_length); /* inline for ring buffer fast paths */ static void * rb_event_data(struct ring_buffer_event *event) { BUG_ON(event->type != RINGBUF_TYPE_DATA); /* If length is in len field, then array[0] has the data */ if (event->len) return (void *)&event->array[0]; /* Otherwise length is in array[0] and array[1] has the data */ return (void *)&event->array[1]; } /** * ring_buffer_event_data - return the data of the event * @event: the event to get the data from */ void *ring_buffer_event_data(struct ring_buffer_event *event) { return rb_event_data(event); } EXPORT_SYMBOL_GPL(ring_buffer_event_data); #define for_each_buffer_cpu(buffer, cpu) \ for_each_cpu(cpu, buffer->cpumask) #define TS_SHIFT 27 #define TS_MASK ((1ULL << TS_SHIFT) - 1) #define TS_DELTA_TEST (~TS_MASK) struct buffer_data_page { u64 time_stamp; /* page time stamp */ local_t commit; /* write committed index */ unsigned char data[]; /* data of buffer page */ }; struct buffer_page { local_t write; /* index for next write */ unsigned read; /* index for next read */ struct list_head list; /* list of free pages */ struct buffer_data_page *page; /* Actual data page */ }; static void rb_init_page(struct buffer_data_page *bpage) { local_set(&bpage->commit, 0); } /** * ring_buffer_page_len - the size of data on the page. * @page: The page to read * * Returns the amount of data on the page, including buffer page header. */ size_t ring_buffer_page_len(void *page) { return local_read(&((struct buffer_data_page *)page)->commit) + BUF_PAGE_HDR_SIZE; } /* * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing * this issue out. */ static void free_buffer_page(struct buffer_page *bpage) { free_page((unsigned long)bpage->page); kfree(bpage); } /* * We need to fit the time_stamp delta into 27 bits. */ static inline int test_time_stamp(u64 delta) { if (delta & TS_DELTA_TEST) return 1; return 0; } #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) /* * head_page == tail_page && head == tail then buffer is empty. */ struct ring_buffer_per_cpu { int cpu; struct ring_buffer *buffer; spinlock_t reader_lock; /* serialize readers */ raw_spinlock_t lock; struct lock_class_key lock_key; struct list_head pages; struct buffer_page *head_page; /* read from head */ struct buffer_page *tail_page; /* write to tail */ struct buffer_page *commit_page; /* committed pages */ struct buffer_page *reader_page; unsigned long overrun; unsigned long entries; u64 write_stamp; u64 read_stamp; atomic_t record_disabled; }; struct ring_buffer { unsigned pages; unsigned flags; int cpus; atomic_t record_disabled; cpumask_var_t cpumask; struct mutex mutex; struct ring_buffer_per_cpu **buffers; #ifdef CONFIG_HOTPLUG_CPU struct notifier_block cpu_notify; #endif u64 (*clock)(void); }; struct ring_buffer_iter { struct ring_buffer_per_cpu *cpu_buffer; unsigned long head; struct buffer_page *head_page; u64 read_stamp; }; /* buffer may be either ring_buffer or ring_buffer_per_cpu */ #define RB_WARN_ON(buffer, cond) \ ({ \ int _____ret = unlikely(cond); \ if (_____ret) { \ atomic_inc(&buffer->record_disabled); \ WARN_ON(1); \ } \ _____ret; \ }) /* Up this if you want to test the TIME_EXTENTS and normalization */ #define DEBUG_SHIFT 0 u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) { u64 time; preempt_disable_notrace(); /* shift to debug/test normalization and TIME_EXTENTS */ time = buffer->clock() << DEBUG_SHIFT; preempt_enable_no_resched_notrace(); return time; } EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, int cpu, u64 *ts) { /* Just stupid testing the normalize function and deltas */ *ts >>= DEBUG_SHIFT; } EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); /** * check_pages - integrity check of buffer pages * @cpu_buffer: CPU buffer with pages to test * * As a safety measure we check to make sure the data pages have not * been corrupted. */ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) { struct list_head *head = &cpu_buffer->pages; struct buffer_page *bpage, *tmp; if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) return -1; if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) return -1; list_for_each_entry_safe(bpage, tmp, head, list) { if (RB_WARN_ON(cpu_buffer, bpage->list.next->prev != &bpage->list)) return -1; if (RB_WARN_ON(cpu_buffer, bpage->list.prev->next != &bpage->list)) return -1; } return 0; } static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) { struct list_head *head = &cpu_buffer->pages; struct buffer_page *bpage, *tmp; unsigned long addr; LIST_HEAD(pages); unsigned i; for (i = 0; i < nr_pages; i++) { bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu_buffer->cpu)); if (!bpage) goto free_pages; list_add(&bpage->list, &pages); addr = __get_free_page(GFP_KERNEL); if (!addr) goto free_pages; bpage->page = (void *)addr; rb_init_page(bpage->page); } list_splice(&pages, head); rb_check_pages(cpu_buffer); return 0; free_pages: list_for_each_entry_safe(bpage, tmp, &pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } return -ENOMEM; } static struct ring_buffer_per_cpu * rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage; unsigned long addr; int ret; cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); if (!cpu_buffer) return NULL; cpu_buffer->cpu = cpu; cpu_buffer->buffer = buffer; spin_lock_init(&cpu_buffer->reader_lock); cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; INIT_LIST_HEAD(&cpu_buffer->pages); bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); if (!bpage) goto fail_free_buffer; cpu_buffer->reader_page = bpage; addr = __get_free_page(GFP_KERNEL); if (!addr) goto fail_free_reader; bpage->page = (void *)addr; rb_init_page(bpage->page); INIT_LIST_HEAD(&cpu_buffer->reader_page->list); ret = rb_allocate_pages(cpu_buffer, buffer->pages); if (ret < 0) goto fail_free_reader; cpu_buffer->head_page = list_entry(cpu_buffer->pages.next, struct buffer_page, list); cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; return cpu_buffer; fail_free_reader: free_buffer_page(cpu_buffer->reader_page); fail_free_buffer: kfree(cpu_buffer); return NULL; } static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) { struct list_head *head = &cpu_buffer->pages; struct buffer_page *bpage, *tmp; list_del_init(&cpu_buffer->reader_page->list); free_buffer_page(cpu_buffer->reader_page); list_for_each_entry_safe(bpage, tmp, head, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } kfree(cpu_buffer); } /* * Causes compile errors if the struct buffer_page gets bigger * than the struct page. */ extern int ring_buffer_page_too_big(void); #ifdef CONFIG_HOTPLUG_CPU static int __cpuinit rb_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu); #endif /** * ring_buffer_alloc - allocate a new ring_buffer * @size: the size in bytes per cpu that is needed. * @flags: attributes to set for the ring buffer. * * Currently the only flag that is available is the RB_FL_OVERWRITE * flag. This flag means that the buffer will overwrite old data * when the buffer wraps. If this flag is not set, the buffer will * drop data when the tail hits the head. */ struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags) { struct ring_buffer *buffer; int bsize; int cpu; /* Paranoid! Optimizes out when all is well */ if (sizeof(struct buffer_page) > sizeof(struct page)) ring_buffer_page_too_big(); /* keep it in its own cache line */ buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), GFP_KERNEL); if (!buffer) return NULL; if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) goto fail_free_buffer; buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); buffer->flags = flags; buffer->clock = trace_clock_local; /* need at least two pages */ if (buffer->pages == 1) buffer->pages++; /* * In case of non-hotplug cpu, if the ring-buffer is allocated * in early initcall, it will not be notified of secondary cpus. * In that off case, we need to allocate for all possible cpus. */ #ifdef CONFIG_HOTPLUG_CPU get_online_cpus(); cpumask_copy(buffer->cpumask, cpu_online_mask); #else cpumask_copy(buffer->cpumask, cpu_possible_mask); #endif buffer->cpus = nr_cpu_ids; bsize = sizeof(void *) * nr_cpu_ids; buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), GFP_KERNEL); if (!buffer->buffers) goto fail_free_cpumask; for_each_buffer_cpu(buffer, cpu) { buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, cpu); if (!buffer->buffers[cpu]) goto fail_free_buffers; } #ifdef CONFIG_HOTPLUG_CPU buffer->cpu_notify.notifier_call = rb_cpu_notify; buffer->cpu_notify.priority = 0; register_cpu_notifier(&buffer->cpu_notify); #endif put_online_cpus(); mutex_init(&buffer->mutex); return buffer; fail_free_buffers: for_each_buffer_cpu(buffer, cpu) { if (buffer->buffers[cpu]) rb_free_cpu_buffer(buffer->buffers[cpu]); } kfree(buffer->buffers); fail_free_cpumask: free_cpumask_var(buffer->cpumask); put_online_cpus(); fail_free_buffer: kfree(buffer); return NULL; } EXPORT_SYMBOL_GPL(ring_buffer_alloc); /** * ring_buffer_free - free a ring buffer. * @buffer: the buffer to free. */ void ring_buffer_free(struct ring_buffer *buffer) { int cpu; get_online_cpus(); #ifdef CONFIG_HOTPLUG_CPU unregister_cpu_notifier(&buffer->cpu_notify); #endif for_each_buffer_cpu(buffer, cpu) rb_free_cpu_buffer(buffer->buffers[cpu]); put_online_cpus(); free_cpumask_var(buffer->cpumask); kfree(buffer); } EXPORT_SYMBOL_GPL(ring_buffer_free); void ring_buffer_set_clock(struct ring_buffer *buffer, u64 (*clock)(void)) { buffer->clock = clock; } static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); static void rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) { struct buffer_page *bpage; struct list_head *p; unsigned i; atomic_inc(&cpu_buffer->record_disabled); synchronize_sched(); for (i = 0; i < nr_pages; i++) { if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages))) return; p = cpu_buffer->pages.next; bpage = list_entry(p, struct buffer_page, list); list_del_init(&bpage->list); free_buffer_page(bpage); } if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages))) return; rb_reset_cpu(cpu_buffer); rb_check_pages(cpu_buffer); atomic_dec(&cpu_buffer->record_disabled); } static void rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, struct list_head *pages, unsigned nr_pages) { struct buffer_page *bpage; struct list_head *p; unsigned i; atomic_inc(&cpu_buffer->record_disabled); synchronize_sched(); for (i = 0; i < nr_pages; i++) { if (RB_WARN_ON(cpu_buffer, list_empty(pages))) return; p = pages->next; bpage = list_entry(p, struct buffer_page, list); list_del_init(&bpage->list); list_add_tail(&bpage->list, &cpu_buffer->pages); } rb_reset_cpu(cpu_buffer); rb_check_pages(cpu_buffer); atomic_dec(&cpu_buffer->record_disabled); } /** * ring_buffer_resize - resize the ring buffer * @buffer: the buffer to resize. * @size: the new size. * * The tracer is responsible for making sure that the buffer is * not being used while changing the size. * Note: We may be able to change the above requirement by using * RCU synchronizations. * * Minimum size is 2 * BUF_PAGE_SIZE. * * Returns -1 on failure. */ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) { struct ring_buffer_per_cpu *cpu_buffer; unsigned nr_pages, rm_pages, new_pages; struct buffer_page *bpage, *tmp; unsigned long buffer_size; unsigned long addr; LIST_HEAD(pages); int i, cpu; /* * Always succeed at resizing a non-existent buffer: */ if (!buffer) return size; size = DIV_ROUND_UP(size, BUF_PAGE_SIZE); size *= BUF_PAGE_SIZE; buffer_size = buffer->pages * BUF_PAGE_SIZE; /* we need a minimum of two pages */ if (size < BUF_PAGE_SIZE * 2) size = BUF_PAGE_SIZE * 2; if (size == buffer_size) return size; mutex_lock(&buffer->mutex); get_online_cpus(); nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); if (size < buffer_size) { /* easy case, just free pages */ if (RB_WARN_ON(buffer, nr_pages >= buffer->pages)) goto out_fail; rm_pages = buffer->pages - nr_pages; for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; rb_remove_pages(cpu_buffer, rm_pages); } goto out; } /* * This is a bit more difficult. We only want to add pages * when we can allocate enough for all CPUs. We do this * by allocating all the pages and storing them on a local * link list. If we succeed in our allocation, then we * add these pages to the cpu_buffers. Otherwise we just free * them all and return -ENOMEM; */ if (RB_WARN_ON(buffer, nr_pages <= buffer->pages)) goto out_fail; new_pages = nr_pages - buffer->pages; for_each_buffer_cpu(buffer, cpu) { for (i = 0; i < new_pages; i++) { bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), GFP_KERNEL, cpu_to_node(cpu)); if (!bpage) goto free_pages; list_add(&bpage->list, &pages); addr = __get_free_page(GFP_KERNEL); if (!addr) goto free_pages; bpage->page = (void *)addr; rb_init_page(bpage->page); } } for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; rb_insert_pages(cpu_buffer, &pages, new_pages); } if (RB_WARN_ON(buffer, !list_empty(&pages))) goto out_fail; out: buffer->pages = nr_pages; put_online_cpus(); mutex_unlock(&buffer->mutex); return size; free_pages: list_for_each_entry_safe(bpage, tmp, &pages, list) { list_del_init(&bpage->list); free_buffer_page(bpage); } put_online_cpus(); mutex_unlock(&buffer->mutex); return -ENOMEM; /* * Something went totally wrong, and we are too paranoid * to even clean up the mess. */ out_fail: put_online_cpus(); mutex_unlock(&buffer->mutex); return -1; } EXPORT_SYMBOL_GPL(ring_buffer_resize); static inline int rb_null_event(struct ring_buffer_event *event) { return event->type == RINGBUF_TYPE_PADDING; } static inline void * __rb_data_page_index(struct buffer_data_page *bpage, unsigned index) { return bpage->data + index; } static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) { return bpage->page->data + index; } static inline struct ring_buffer_event * rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) { return __rb_page_index(cpu_buffer->reader_page, cpu_buffer->reader_page->read); } static inline struct ring_buffer_event * rb_head_event(struct ring_buffer_per_cpu *cpu_buffer) { return __rb_page_index(cpu_buffer->head_page, cpu_buffer->head_page->read); } static inline struct ring_buffer_event * rb_iter_head_event(struct ring_buffer_iter *iter) { return __rb_page_index(iter->head_page, iter->head); } static inline unsigned rb_page_write(struct buffer_page *bpage) { return local_read(&bpage->write); } static inline unsigned rb_page_commit(struct buffer_page *bpage) { return local_read(&bpage->page->commit); } /* Size is determined by what has been commited */ static inline unsigned rb_page_size(struct buffer_page *bpage) { return rb_page_commit(bpage); } static inline unsigned rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) { return rb_page_commit(cpu_buffer->commit_page); } static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer) { return rb_page_commit(cpu_buffer->head_page); } /* * When the tail hits the head and the buffer is in overwrite mode, * the head jumps to the next page and all content on the previous * page is discarded. But before doing so, we update the overrun * variable of the buffer. */ static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer) { struct ring_buffer_event *event; unsigned long head; for (head = 0; head < rb_head_size(cpu_buffer); head += rb_event_length(event)) { event = __rb_page_index(cpu_buffer->head_page, head); if (RB_WARN_ON(cpu_buffer, rb_null_event(event))) return; /* Only count data entries */ if (event->type != RINGBUF_TYPE_DATA) continue; cpu_buffer->overrun++; cpu_buffer->entries--; } } static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_page **bpage) { struct list_head *p = (*bpage)->list.next; if (p == &cpu_buffer->pages) p = p->next; *bpage = list_entry(p, struct buffer_page, list); } static inline unsigned rb_event_index(struct ring_buffer_event *event) { unsigned long addr = (unsigned long)event; return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE); } static int rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { unsigned long addr = (unsigned long)event; unsigned long index; index = rb_event_index(event); addr &= PAGE_MASK; return cpu_buffer->commit_page->page == (void *)addr && rb_commit_index(cpu_buffer) == index; } static void rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { unsigned long addr = (unsigned long)event; unsigned long index; index = rb_event_index(event); addr &= PAGE_MASK; while (cpu_buffer->commit_page->page != (void *)addr) { if (RB_WARN_ON(cpu_buffer, cpu_buffer->commit_page == cpu_buffer->tail_page)) return; cpu_buffer->commit_page->page->commit = cpu_buffer->commit_page->write; rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); cpu_buffer->write_stamp = cpu_buffer->commit_page->page->time_stamp; } /* Now set the commit to the event's index */ local_set(&cpu_buffer->commit_page->page->commit, index); } static void rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) { /* * We only race with interrupts and NMIs on this CPU. * If we own the commit event, then we can commit * all others that interrupted us, since the interruptions * are in stack format (they finish before they come * back to us). This allows us to do a simple loop to * assign the commit to the tail. */ again: while (cpu_buffer->commit_page != cpu_buffer->tail_page) { cpu_buffer->commit_page->page->commit = cpu_buffer->commit_page->write; rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); cpu_buffer->write_stamp = cpu_buffer->commit_page->page->time_stamp; /* add barrier to keep gcc from optimizing too much */ barrier(); } while (rb_commit_index(cpu_buffer) != rb_page_write(cpu_buffer->commit_page)) { cpu_buffer->commit_page->page->commit = cpu_buffer->commit_page->write; barrier(); } /* again, keep gcc from optimizing */ barrier(); /* * If an interrupt came in just after the first while loop * and pushed the tail page forward, we will be left with * a dangling commit that will never go forward. */ if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page)) goto again; } static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer) { cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp; cpu_buffer->reader_page->read = 0; } static void rb_inc_iter(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; /* * The iterator could be on the reader page (it starts there). * But the head could have moved, since the reader was * found. Check for this case and assign the iterator * to the head page instead of next. */ if (iter->head_page == cpu_buffer->reader_page) iter->head_page = cpu_buffer->head_page; else rb_inc_page(cpu_buffer, &iter->head_page); iter->read_stamp = iter->head_page->page->time_stamp; iter->head = 0; } /** * ring_buffer_update_event - update event type and data * @event: the even to update * @type: the type of event * @length: the size of the event field in the ring buffer * * Update the type and data fields of the event. The length * is the actual size that is written to the ring buffer, * and with this, we can determine what to place into the * data field. */ static void rb_update_event(struct ring_buffer_event *event, unsigned type, unsigned length) { event->type = type; switch (type) { case RINGBUF_TYPE_PADDING: break; case RINGBUF_TYPE_TIME_EXTEND: event->len = DIV_ROUND_UP(RB_LEN_TIME_EXTEND, RB_ALIGNMENT); break; case RINGBUF_TYPE_TIME_STAMP: event->len = DIV_ROUND_UP(RB_LEN_TIME_STAMP, RB_ALIGNMENT); break; case RINGBUF_TYPE_DATA: length -= RB_EVNT_HDR_SIZE; if (length > RB_MAX_SMALL_DATA) { event->len = 0; event->array[0] = length; } else event->len = DIV_ROUND_UP(length, RB_ALIGNMENT); break; default: BUG(); } } static unsigned rb_calculate_event_length(unsigned length) { struct ring_buffer_event event; /* Used only for sizeof array */ /* zero length can cause confusions */ if (!length) length = 1; if (length > RB_MAX_SMALL_DATA) length += sizeof(event.array[0]); length += RB_EVNT_HDR_SIZE; length = ALIGN(length, RB_ALIGNMENT); return length; } static struct ring_buffer_event * __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, unsigned type, unsigned long length, u64 *ts) { struct buffer_page *tail_page, *head_page, *reader_page, *commit_page; unsigned long tail, write; struct ring_buffer *buffer = cpu_buffer->buffer; struct ring_buffer_event *event; unsigned long flags; bool lock_taken = false; commit_page = cpu_buffer->commit_page; /* we just need to protect against interrupts */ barrier(); tail_page = cpu_buffer->tail_page; write = local_add_return(length, &tail_page->write); tail = write - length; /* See if we shot pass the end of this buffer page */ if (write > BUF_PAGE_SIZE) { struct buffer_page *next_page = tail_page; local_irq_save(flags); /* * Since the write to the buffer is still not * fully lockless, we must be careful with NMIs. * The locks in the writers are taken when a write * crosses to a new page. The locks protect against * races with the readers (this will soon be fixed * with a lockless solution). * * Because we can not protect against NMIs, and we * want to keep traces reentrant, we need to manage * what happens when we are in an NMI. * * NMIs can happen after we take the lock. * If we are in an NMI, only take the lock * if it is not already taken. Otherwise * simply fail. */ if (unlikely(in_nmi())) { if (!__raw_spin_trylock(&cpu_buffer->lock)) goto out_reset; } else __raw_spin_lock(&cpu_buffer->lock); lock_taken = true; rb_inc_page(cpu_buffer, &next_page); head_page = cpu_buffer->head_page; reader_page = cpu_buffer->reader_page; /* we grabbed the lock before incrementing */ if (RB_WARN_ON(cpu_buffer, next_page == reader_page)) goto out_reset; /* * If for some reason, we had an interrupt storm that made * it all the way around the buffer, bail, and warn * about it. */ if (unlikely(next_page == commit_page)) { WARN_ON_ONCE(1); goto out_reset; } if (next_page == head_page) { if (!(buffer->flags & RB_FL_OVERWRITE)) goto out_reset; /* tail_page has not moved yet? */ if (tail_page == cpu_buffer->tail_page) { /* count overflows */ rb_update_overflow(cpu_buffer); rb_inc_page(cpu_buffer, &head_page); cpu_buffer->head_page = head_page; cpu_buffer->head_page->read = 0; } } /* * If the tail page is still the same as what we think * it is, then it is up to us to update the tail * pointer. */ if (tail_page == cpu_buffer->tail_page) { local_set(&next_page->write, 0); local_set(&next_page->page->commit, 0); cpu_buffer->tail_page = next_page; /* reread the time stamp */ *ts = ring_buffer_time_stamp(buffer, cpu_buffer->cpu); cpu_buffer->tail_page->page->time_stamp = *ts; } /* * The actual tail page has moved forward. */ if (tail < BUF_PAGE_SIZE) { /* Mark the rest of the page with padding */ event = __rb_page_index(tail_page, tail); event->type = RINGBUF_TYPE_PADDING; } if (tail <= BUF_PAGE_SIZE) /* Set the write back to the previous setting */ local_set(&tail_page->write, tail); /* * If this was a commit entry that failed, * increment that too */ if (tail_page == cpu_buffer->commit_page && tail == rb_commit_index(cpu_buffer)) { rb_set_commit_to_write(cpu_buffer); } __raw_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); /* fail and let the caller try again */ return ERR_PTR(-EAGAIN); } /* We reserved something on the buffer */ if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE)) return NULL; event = __rb_page_index(tail_page, tail); rb_update_event(event, type, length); /* * If this is a commit and the tail is zero, then update * this page's time stamp. */ if (!tail && rb_is_commit(cpu_buffer, event)) cpu_buffer->commit_page->page->time_stamp = *ts; return event; out_reset: /* reset write */ if (tail <= BUF_PAGE_SIZE) local_set(&tail_page->write, tail); if (likely(lock_taken)) __raw_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); return NULL; } static int rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts, u64 *delta) { struct ring_buffer_event *event; static int once; int ret; if (unlikely(*delta > (1ULL << 59) && !once++)) { printk(KERN_WARNING "Delta way too big! %llu" " ts=%llu write stamp = %llu\n", (unsigned long long)*delta, (unsigned long long)*ts, (unsigned long long)cpu_buffer->write_stamp); WARN_ON(1); } /* * The delta is too big, we to add a * new timestamp. */ event = __rb_reserve_next(cpu_buffer, RINGBUF_TYPE_TIME_EXTEND, RB_LEN_TIME_EXTEND, ts); if (!event) return -EBUSY; if (PTR_ERR(event) == -EAGAIN) return -EAGAIN; /* Only a commited time event can update the write stamp */ if (rb_is_commit(cpu_buffer, event)) { /* * If this is the first on the page, then we need to * update the page itself, and just put in a zero. */ if (rb_event_index(event)) { event->time_delta = *delta & TS_MASK; event->array[0] = *delta >> TS_SHIFT; } else { cpu_buffer->commit_page->page->time_stamp = *ts; event->time_delta = 0; event->array[0] = 0; } cpu_buffer->write_stamp = *ts; /* let the caller know this was the commit */ ret = 1; } else { /* Darn, this is just wasted space */ event->time_delta = 0; event->array[0] = 0; ret = 0; } *delta = 0; return ret; } static struct ring_buffer_event * rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, unsigned type, unsigned long length) { struct ring_buffer_event *event; u64 ts, delta; int commit = 0; int nr_loops = 0; again: /* * We allow for interrupts to reenter here and do a trace. * If one does, it will cause this original code to loop * back here. Even with heavy interrupts happening, this * should only happen a few times in a row. If this happens * 1000 times in a row, there must be either an interrupt * storm or we have something buggy. * Bail! */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) return NULL; ts = ring_buffer_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu); /* * Only the first commit can update the timestamp. * Yes there is a race here. If an interrupt comes in * just after the conditional and it traces too, then it * will also check the deltas. More than one timestamp may * also be made. But only the entry that did the actual * commit will be something other than zero. */ if (cpu_buffer->tail_page == cpu_buffer->commit_page && rb_page_write(cpu_buffer->tail_page) == rb_commit_index(cpu_buffer)) { delta = ts - cpu_buffer->write_stamp; /* make sure this delta is calculated here */ barrier(); /* Did the write stamp get updated already? */ if (unlikely(ts < cpu_buffer->write_stamp)) delta = 0; if (test_time_stamp(delta)) { commit = rb_add_time_stamp(cpu_buffer, &ts, &delta); if (commit == -EBUSY) return NULL; if (commit == -EAGAIN) goto again; RB_WARN_ON(cpu_buffer, commit < 0); } } else /* Non commits have zero deltas */ delta = 0; event = __rb_reserve_next(cpu_buffer, type, length, &ts); if (PTR_ERR(event) == -EAGAIN) goto again; if (!event) { if (unlikely(commit)) /* * Ouch! We needed a timestamp and it was commited. But * we didn't get our event reserved. */ rb_set_commit_to_write(cpu_buffer); return NULL; } /* * If the timestamp was commited, make the commit our entry * now so that we will update it when needed. */ if (commit) rb_set_commit_event(cpu_buffer, event); else if (!rb_is_commit(cpu_buffer, event)) delta = 0; event->time_delta = delta; return event; } static DEFINE_PER_CPU(int, rb_need_resched); /** * ring_buffer_lock_reserve - reserve a part of the buffer * @buffer: the ring buffer to reserve from * @length: the length of the data to reserve (excluding event header) * * Returns a reseverd event on the ring buffer to copy directly to. * The user of this interface will need to get the body to write into * and can use the ring_buffer_event_data() interface. * * The length is the length of the data needed, not the event length * which also includes the event header. * * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. * If NULL is returned, then nothing has been allocated or locked. */ struct ring_buffer_event * ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; int cpu, resched; if (ring_buffer_flags != RB_BUFFERS_ON) return NULL; if (atomic_read(&buffer->record_disabled)) return NULL; /* If we are tracing schedule, we don't want to recurse */ resched = ftrace_preempt_disable(); cpu = raw_smp_processor_id(); if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out; cpu_buffer = buffer->buffers[cpu]; if (atomic_read(&cpu_buffer->record_disabled)) goto out; length = rb_calculate_event_length(length); if (length > BUF_PAGE_SIZE) goto out; event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length); if (!event) goto out; /* * Need to store resched state on this cpu. * Only the first needs to. */ if (preempt_count() == 1) per_cpu(rb_need_resched, cpu) = resched; return event; out: ftrace_preempt_enable(resched); return NULL; } EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { cpu_buffer->entries++; /* Only process further if we own the commit */ if (!rb_is_commit(cpu_buffer, event)) return; cpu_buffer->write_stamp += event->time_delta; rb_set_commit_to_write(cpu_buffer); } /** * ring_buffer_unlock_commit - commit a reserved * @buffer: The buffer to commit to * @event: The event pointer to commit. * * This commits the data to the ring buffer, and releases any locks held. * * Must be paired with ring_buffer_lock_reserve. */ int ring_buffer_unlock_commit(struct ring_buffer *buffer, struct ring_buffer_event *event) { struct ring_buffer_per_cpu *cpu_buffer; int cpu = raw_smp_processor_id(); cpu_buffer = buffer->buffers[cpu]; rb_commit(cpu_buffer, event); /* * Only the last preempt count needs to restore preemption. */ if (preempt_count() == 1) ftrace_preempt_enable(per_cpu(rb_need_resched, cpu)); else preempt_enable_no_resched_notrace(); return 0; } EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); /** * ring_buffer_write - write data to the buffer without reserving * @buffer: The ring buffer to write to. * @length: The length of the data being written (excluding the event header) * @data: The data to write to the buffer. * * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as * one function. If you already have the data to write to the buffer, it * may be easier to simply call this function. * * Note, like ring_buffer_lock_reserve, the length is the length of the data * and not the length of the event which would hold the header. */ int ring_buffer_write(struct ring_buffer *buffer, unsigned long length, void *data) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; unsigned long event_length; void *body; int ret = -EBUSY; int cpu, resched; if (ring_buffer_flags != RB_BUFFERS_ON) return -EBUSY; if (atomic_read(&buffer->record_disabled)) return -EBUSY; resched = ftrace_preempt_disable(); cpu = raw_smp_processor_id(); if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out; cpu_buffer = buffer->buffers[cpu]; if (atomic_read(&cpu_buffer->record_disabled)) goto out; event_length = rb_calculate_event_length(length); event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, event_length); if (!event) goto out; body = rb_event_data(event); memcpy(body, data, length); rb_commit(cpu_buffer, event); ret = 0; out: ftrace_preempt_enable(resched); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_write); static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) { struct buffer_page *reader = cpu_buffer->reader_page; struct buffer_page *head = cpu_buffer->head_page; struct buffer_page *commit = cpu_buffer->commit_page; return reader->read == rb_page_commit(reader) && (commit == reader || (commit == head && head->read == rb_page_commit(commit))); } /** * ring_buffer_record_disable - stop all writes into the buffer * @buffer: The ring buffer to stop writes to. * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * The caller should call synchronize_sched() after this. */ void ring_buffer_record_disable(struct ring_buffer *buffer) { atomic_inc(&buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_disable); /** * ring_buffer_record_enable - enable writes to the buffer * @buffer: The ring buffer to enable writes * * Note, multiple disables will need the same number of enables * to truely enable the writing (much like preempt_disable). */ void ring_buffer_record_enable(struct ring_buffer *buffer) { atomic_dec(&buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_enable); /** * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer * @buffer: The ring buffer to stop writes to. * @cpu: The CPU buffer to stop * * This prevents all writes to the buffer. Any attempt to write * to the buffer after this will fail and return NULL. * * The caller should call synchronize_sched() after this. */ void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return; cpu_buffer = buffer->buffers[cpu]; atomic_inc(&cpu_buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); /** * ring_buffer_record_enable_cpu - enable writes to the buffer * @buffer: The ring buffer to enable writes * @cpu: The CPU to enable. * * Note, multiple disables will need the same number of enables * to truely enable the writing (much like preempt_disable). */ void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return; cpu_buffer = buffer->buffers[cpu]; atomic_dec(&cpu_buffer->record_disabled); } EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); /** * ring_buffer_entries_cpu - get the number of entries in a cpu buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to get the entries from. */ unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; ret = cpu_buffer->entries; return ret; } EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); /** * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer * @buffer: The ring buffer * @cpu: The per CPU buffer to get the number of overruns from */ unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; cpu_buffer = buffer->buffers[cpu]; ret = cpu_buffer->overrun; return ret; } EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu); /** * ring_buffer_entries - get the number of entries in a buffer * @buffer: The ring buffer * * Returns the total number of entries in the ring buffer * (all CPU entries) */ unsigned long ring_buffer_entries(struct ring_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long entries = 0; int cpu; /* if you care about this being correct, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; entries += cpu_buffer->entries; } return entries; } EXPORT_SYMBOL_GPL(ring_buffer_entries); /** * ring_buffer_overrun_cpu - get the number of overruns in buffer * @buffer: The ring buffer * * Returns the total number of overruns in the ring buffer * (all CPU entries) */ unsigned long ring_buffer_overruns(struct ring_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long overruns = 0; int cpu; /* if you care about this being correct, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; overruns += cpu_buffer->overrun; } return overruns; } EXPORT_SYMBOL_GPL(ring_buffer_overruns); static void rb_iter_reset(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; /* Iterator usage is expected to have record disabled */ if (list_empty(&cpu_buffer->reader_page->list)) { iter->head_page = cpu_buffer->head_page; iter->head = cpu_buffer->head_page->read; } else { iter->head_page = cpu_buffer->reader_page; iter->head = cpu_buffer->reader_page->read; } if (iter->head) iter->read_stamp = cpu_buffer->read_stamp; else iter->read_stamp = iter->head_page->page->time_stamp; } /** * ring_buffer_iter_reset - reset an iterator * @iter: The iterator to reset * * Resets the iterator, so that it will start from the beginning * again. */ void ring_buffer_iter_reset(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; if (!iter) return; cpu_buffer = iter->cpu_buffer; spin_lock_irqsave(&cpu_buffer->reader_lock, flags); rb_iter_reset(iter); spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); /** * ring_buffer_iter_empty - check if an iterator has no more to read * @iter: The iterator to check */ int ring_buffer_iter_empty(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer; cpu_buffer = iter->cpu_buffer; return iter->head_page == cpu_buffer->commit_page && iter->head == rb_commit_index(cpu_buffer); } EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); static void rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event) { u64 delta; switch (event->type) { case RINGBUF_TYPE_PADDING: return; case RINGBUF_TYPE_TIME_EXTEND: delta = event->array[0]; delta <<= TS_SHIFT; delta += event->time_delta; cpu_buffer->read_stamp += delta; return; case RINGBUF_TYPE_TIME_STAMP: /* FIXME: not implemented */ return; case RINGBUF_TYPE_DATA: cpu_buffer->read_stamp += event->time_delta; return; default: BUG(); } return; } static void rb_update_iter_read_stamp(struct ring_buffer_iter *iter, struct ring_buffer_event *event) { u64 delta; switch (event->type) { case RINGBUF_TYPE_PADDING: return; case RINGBUF_TYPE_TIME_EXTEND: delta = event->array[0]; delta <<= TS_SHIFT; delta += event->time_delta; iter->read_stamp += delta; return; case RINGBUF_TYPE_TIME_STAMP: /* FIXME: not implemented */ return; case RINGBUF_TYPE_DATA: iter->read_stamp += event->time_delta; return; default: BUG(); } return; } static struct buffer_page * rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer) { struct buffer_page *reader = NULL; unsigned long flags; int nr_loops = 0; local_irq_save(flags); __raw_spin_lock(&cpu_buffer->lock); again: /* * This should normally only loop twice. But because the * start of the reader inserts an empty page, it causes * a case where we will loop three times. There should be no * reason to loop four times (that I know of). */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) { reader = NULL; goto out; } reader = cpu_buffer->reader_page; /* If there's more to read, return this page */ if (cpu_buffer->reader_page->read < rb_page_size(reader)) goto out; /* Never should we have an index greater than the size */ if (RB_WARN_ON(cpu_buffer, cpu_buffer->reader_page->read > rb_page_size(reader))) goto out; /* check if we caught up to the tail */ reader = NULL; if (cpu_buffer->commit_page == cpu_buffer->reader_page) goto out; /* * Splice the empty reader page into the list around the head. * Reset the reader page to size zero. */ reader = cpu_buffer->head_page; cpu_buffer->reader_page->list.next = reader->list.next; cpu_buffer->reader_page->list.prev = reader->list.prev; local_set(&cpu_buffer->reader_page->write, 0); local_set(&cpu_buffer->reader_page->page->commit, 0); /* Make the reader page now replace the head */ reader->list.prev->next = &cpu_buffer->reader_page->list; reader->list.next->prev = &cpu_buffer->reader_page->list; /* * If the tail is on the reader, then we must set the head * to the inserted page, otherwise we set it one before. */ cpu_buffer->head_page = cpu_buffer->reader_page; if (cpu_buffer->commit_page != reader) rb_inc_page(cpu_buffer, &cpu_buffer->head_page); /* Finally update the reader page to the new head */ cpu_buffer->reader_page = reader; rb_reset_reader_page(cpu_buffer); goto again; out: __raw_spin_unlock(&cpu_buffer->lock); local_irq_restore(flags); return reader; } static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) { struct ring_buffer_event *event; struct buffer_page *reader; unsigned length; reader = rb_get_reader_page(cpu_buffer); /* This function should not be called when buffer is empty */ if (RB_WARN_ON(cpu_buffer, !reader)) return; event = rb_reader_event(cpu_buffer); if (event->type == RINGBUF_TYPE_DATA) cpu_buffer->entries--; rb_update_read_stamp(cpu_buffer, event); length = rb_event_length(event); cpu_buffer->reader_page->read += length; } static void rb_advance_iter(struct ring_buffer_iter *iter) { struct ring_buffer *buffer; struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; unsigned length; cpu_buffer = iter->cpu_buffer; buffer = cpu_buffer->buffer; /* * Check if we are at the end of the buffer. */ if (iter->head >= rb_page_size(iter->head_page)) { if (RB_WARN_ON(buffer, iter->head_page == cpu_buffer->commit_page)) return; rb_inc_iter(iter); return; } event = rb_iter_head_event(iter); length = rb_event_length(event); /* * This should not be called to advance the header if we are * at the tail of the buffer. */ if (RB_WARN_ON(cpu_buffer, (iter->head_page == cpu_buffer->commit_page) && (iter->head + length > rb_commit_index(cpu_buffer)))) return; rb_update_iter_read_stamp(iter, event); iter->head += length; /* check for end of page padding */ if ((iter->head >= rb_page_size(iter->head_page)) && (iter->head_page != cpu_buffer->commit_page)) rb_advance_iter(iter); } static struct ring_buffer_event * rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; struct buffer_page *reader; int nr_loops = 0; cpu_buffer = buffer->buffers[cpu]; again: /* * We repeat when a timestamp is encountered. It is possible * to get multiple timestamps from an interrupt entering just * as one timestamp is about to be written. The max times * that this can happen is the number of nested interrupts we * can have. Nesting 10 deep of interrupts is clearly * an anomaly. */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10)) return NULL; reader = rb_get_reader_page(cpu_buffer); if (!reader) return NULL; event = rb_reader_event(cpu_buffer); switch (event->type) { case RINGBUF_TYPE_PADDING: RB_WARN_ON(cpu_buffer, 1); rb_advance_reader(cpu_buffer); return NULL; case RINGBUF_TYPE_TIME_EXTEND: /* Internal data, OK to advance */ rb_advance_reader(cpu_buffer); goto again; case RINGBUF_TYPE_TIME_STAMP: /* FIXME: not implemented */ rb_advance_reader(cpu_buffer); goto again; case RINGBUF_TYPE_DATA: if (ts) { *ts = cpu_buffer->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(buffer, cpu_buffer->cpu, ts); } return event; default: BUG(); } return NULL; } EXPORT_SYMBOL_GPL(ring_buffer_peek); static struct ring_buffer_event * rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) { struct ring_buffer *buffer; struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event; int nr_loops = 0; if (ring_buffer_iter_empty(iter)) return NULL; cpu_buffer = iter->cpu_buffer; buffer = cpu_buffer->buffer; again: /* * We repeat when a timestamp is encountered. It is possible * to get multiple timestamps from an interrupt entering just * as one timestamp is about to be written. The max times * that this can happen is the number of nested interrupts we * can have. Nesting 10 deep of interrupts is clearly * an anomaly. */ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10)) return NULL; if (rb_per_cpu_empty(cpu_buffer)) return NULL; event = rb_iter_head_event(iter); switch (event->type) { case RINGBUF_TYPE_PADDING: rb_inc_iter(iter); goto again; case RINGBUF_TYPE_TIME_EXTEND: /* Internal data, OK to advance */ rb_advance_iter(iter); goto again; case RINGBUF_TYPE_TIME_STAMP: /* FIXME: not implemented */ rb_advance_iter(iter); goto again; case RINGBUF_TYPE_DATA: if (ts) { *ts = iter->read_stamp + event->time_delta; ring_buffer_normalize_time_stamp(buffer, cpu_buffer->cpu, ts); } return event; default: BUG(); } return NULL; } EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); /** * ring_buffer_peek - peek at the next event to be read * @buffer: The ring buffer to read * @cpu: The cpu to peak at * @ts: The timestamp counter of this event. * * This will return the event that will be read next, but does * not consume the data. */ struct ring_buffer_event * ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; unsigned long flags; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL; spin_lock_irqsave(&cpu_buffer->reader_lock, flags); event = rb_buffer_peek(buffer, cpu, ts); spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return event; } /** * ring_buffer_iter_peek - peek at the next event to be read * @iter: The ring buffer iterator * @ts: The timestamp counter of this event. * * This will return the event that will be read next, but does * not increment the iterator. */ struct ring_buffer_event * ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; struct ring_buffer_event *event; unsigned long flags; spin_lock_irqsave(&cpu_buffer->reader_lock, flags); event = rb_iter_peek(iter, ts); spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return event; } /** * ring_buffer_consume - return an event and consume it * @buffer: The ring buffer to get the next event from * * Returns the next event in the ring buffer, and that event is consumed. * Meaning, that sequential reads will keep returning a different event, * and eventually empty the ring buffer if the producer is slower. */ struct ring_buffer_event * ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event = NULL; unsigned long flags; /* might be called in atomic */ preempt_disable(); if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out; cpu_buffer = buffer->buffers[cpu]; spin_lock_irqsave(&cpu_buffer->reader_lock, flags); event = rb_buffer_peek(buffer, cpu, ts); if (!event) goto out_unlock; rb_advance_reader(cpu_buffer); out_unlock: spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); out: preempt_enable(); return event; } EXPORT_SYMBOL_GPL(ring_buffer_consume); /** * ring_buffer_read_start - start a non consuming read of the buffer * @buffer: The ring buffer to read from * @cpu: The cpu buffer to iterate over * * This starts up an iteration through the buffer. It also disables * the recording to the buffer until the reading is finished. * This prevents the reading from being corrupted. This is not * a consuming read, so a producer is not expected. * * Must be paired with ring_buffer_finish. */ struct ring_buffer_iter * ring_buffer_read_start(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_iter *iter; unsigned long flags; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL; iter = kmalloc(sizeof(*iter), GFP_KERNEL); if (!iter) return NULL; cpu_buffer = buffer->buffers[cpu]; iter->cpu_buffer = cpu_buffer; atomic_inc(&cpu_buffer->record_disabled); synchronize_sched(); spin_lock_irqsave(&cpu_buffer->reader_lock, flags); __raw_spin_lock(&cpu_buffer->lock); rb_iter_reset(iter); __raw_spin_unlock(&cpu_buffer->lock); spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return iter; } EXPORT_SYMBOL_GPL(ring_buffer_read_start); /** * ring_buffer_finish - finish reading the iterator of the buffer * @iter: The iterator retrieved by ring_buffer_start * * This re-enables the recording to the buffer, and frees the * iterator. */ void ring_buffer_read_finish(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; atomic_dec(&cpu_buffer->record_disabled); kfree(iter); } EXPORT_SYMBOL_GPL(ring_buffer_read_finish); /** * ring_buffer_read - read the next item in the ring buffer by the iterator * @iter: The ring buffer iterator * @ts: The time stamp of the event read. * * This reads the next event in the ring buffer and increments the iterator. */ struct ring_buffer_event * ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts) { struct ring_buffer_event *event; struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; unsigned long flags; spin_lock_irqsave(&cpu_buffer->reader_lock, flags); event = rb_iter_peek(iter, ts); if (!event) goto out; rb_advance_iter(iter); out: spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return event; } EXPORT_SYMBOL_GPL(ring_buffer_read); /** * ring_buffer_size - return the size of the ring buffer (in bytes) * @buffer: The ring buffer. */ unsigned long ring_buffer_size(struct ring_buffer *buffer) { return BUF_PAGE_SIZE * buffer->pages; } EXPORT_SYMBOL_GPL(ring_buffer_size); static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer) { cpu_buffer->head_page = list_entry(cpu_buffer->pages.next, struct buffer_page, list); local_set(&cpu_buffer->head_page->write, 0); local_set(&cpu_buffer->head_page->page->commit, 0); cpu_buffer->head_page->read = 0; cpu_buffer->tail_page = cpu_buffer->head_page; cpu_buffer->commit_page = cpu_buffer->head_page; INIT_LIST_HEAD(&cpu_buffer->reader_page->list); local_set(&cpu_buffer->reader_page->write, 0); local_set(&cpu_buffer->reader_page->page->commit, 0); cpu_buffer->reader_page->read = 0; cpu_buffer->overrun = 0; cpu_buffer->entries = 0; cpu_buffer->write_stamp = 0; cpu_buffer->read_stamp = 0; } /** * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer * @buffer: The ring buffer to reset a per cpu buffer of * @cpu: The CPU buffer to be reset */ void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; unsigned long flags; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return; spin_lock_irqsave(&cpu_buffer->reader_lock, flags); __raw_spin_lock(&cpu_buffer->lock); rb_reset_cpu(cpu_buffer); __raw_spin_unlock(&cpu_buffer->lock); spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); } EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); /** * ring_buffer_reset - reset a ring buffer * @buffer: The ring buffer to reset all cpu buffers */ void ring_buffer_reset(struct ring_buffer *buffer) { int cpu; for_each_buffer_cpu(buffer, cpu) ring_buffer_reset_cpu(buffer, cpu); } EXPORT_SYMBOL_GPL(ring_buffer_reset); /** * rind_buffer_empty - is the ring buffer empty? * @buffer: The ring buffer to test */ int ring_buffer_empty(struct ring_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; int cpu; /* yes this is racy, but if you don't like the race, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; if (!rb_per_cpu_empty(cpu_buffer)) return 0; } return 1; } EXPORT_SYMBOL_GPL(ring_buffer_empty); /** * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty? * @buffer: The ring buffer * @cpu: The CPU buffer to test */ int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; int ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 1; cpu_buffer = buffer->buffers[cpu]; ret = rb_per_cpu_empty(cpu_buffer); return ret; } EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu); /** * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers * @buffer_a: One buffer to swap with * @buffer_b: The other buffer to swap with * * This function is useful for tracers that want to take a "snapshot" * of a CPU buffer and has another back up buffer lying around. * it is expected that the tracer handles the cpu buffer not being * used at the moment. */ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, struct ring_buffer *buffer_b, int cpu) { struct ring_buffer_per_cpu *cpu_buffer_a; struct ring_buffer_per_cpu *cpu_buffer_b; int ret = -EINVAL; if (!cpumask_test_cpu(cpu, buffer_a->cpumask) || !cpumask_test_cpu(cpu, buffer_b->cpumask)) goto out; /* At least make sure the two buffers are somewhat the same */ if (buffer_a->pages != buffer_b->pages) goto out; ret = -EAGAIN; if (ring_buffer_flags != RB_BUFFERS_ON) goto out; if (atomic_read(&buffer_a->record_disabled)) goto out; if (atomic_read(&buffer_b->record_disabled)) goto out; cpu_buffer_a = buffer_a->buffers[cpu]; cpu_buffer_b = buffer_b->buffers[cpu]; if (atomic_read(&cpu_buffer_a->record_disabled)) goto out; if (atomic_read(&cpu_buffer_b->record_disabled)) goto out; /* * We can't do a synchronize_sched here because this * function can be called in atomic context. * Normally this will be called from the same CPU as cpu. * If not it's up to the caller to protect this. */ atomic_inc(&cpu_buffer_a->record_disabled); atomic_inc(&cpu_buffer_b->record_disabled); buffer_a->buffers[cpu] = cpu_buffer_b; buffer_b->buffers[cpu] = cpu_buffer_a; cpu_buffer_b->buffer = buffer_a; cpu_buffer_a->buffer = buffer_b; atomic_dec(&cpu_buffer_a->record_disabled); atomic_dec(&cpu_buffer_b->record_disabled); ret = 0; out: return ret; } EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); static void rb_remove_entries(struct ring_buffer_per_cpu *cpu_buffer, struct buffer_data_page *bpage, unsigned int offset) { struct ring_buffer_event *event; unsigned long head; __raw_spin_lock(&cpu_buffer->lock); for (head = offset; head < local_read(&bpage->commit); head += rb_event_length(event)) { event = __rb_data_page_index(bpage, head); if (RB_WARN_ON(cpu_buffer, rb_null_event(event))) return; /* Only count data entries */ if (event->type != RINGBUF_TYPE_DATA) continue; cpu_buffer->entries--; } __raw_spin_unlock(&cpu_buffer->lock); } /** * ring_buffer_alloc_read_page - allocate a page to read from buffer * @buffer: the buffer to allocate for. * * This function is used in conjunction with ring_buffer_read_page. * When reading a full page from the ring buffer, these functions * can be used to speed up the process. The calling function should * allocate a few pages first with this function. Then when it * needs to get pages from the ring buffer, it passes the result * of this function into ring_buffer_read_page, which will swap * the page that was allocated, with the read page of the buffer. * * Returns: * The page allocated, or NULL on error. */ void *ring_buffer_alloc_read_page(struct ring_buffer *buffer) { struct buffer_data_page *bpage; unsigned long addr; addr = __get_free_page(GFP_KERNEL); if (!addr) return NULL; bpage = (void *)addr; rb_init_page(bpage); return bpage; } /** * ring_buffer_free_read_page - free an allocated read page * @buffer: the buffer the page was allocate for * @data: the page to free * * Free a page allocated from ring_buffer_alloc_read_page. */ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) { free_page((unsigned long)data); } /** * ring_buffer_read_page - extract a page from the ring buffer * @buffer: buffer to extract from * @data_page: the page to use allocated from ring_buffer_alloc_read_page * @len: amount to extract * @cpu: the cpu of the buffer to extract * @full: should the extraction only happen when the page is full. * * This function will pull out a page from the ring buffer and consume it. * @data_page must be the address of the variable that was returned * from ring_buffer_alloc_read_page. This is because the page might be used * to swap with a page in the ring buffer. * * for example: * rpage = ring_buffer_alloc_read_page(buffer); * if (!rpage) * return error; * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0); * if (ret >= 0) * process_page(rpage, ret); * * When @full is set, the function will not return true unless * the writer is off the reader page. * * Note: it is up to the calling functions to handle sleeps and wakeups. * The ring buffer can be used anywhere in the kernel and can not * blindly call wake_up. The layer that uses the ring buffer must be * responsible for that. * * Returns: * >=0 if data has been transferred, returns the offset of consumed data. * <0 if no data has been transferred. */ int ring_buffer_read_page(struct ring_buffer *buffer, void **data_page, size_t len, int cpu, int full) { struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; struct buffer_data_page *bpage; struct buffer_page *reader; unsigned long flags; unsigned int commit; unsigned int read; u64 save_timestamp; int ret = -1; if (!cpumask_test_cpu(cpu, buffer->cpumask)) goto out; /* * If len is not big enough to hold the page header, then * we can not copy anything. */ if (len <= BUF_PAGE_HDR_SIZE) goto out; len -= BUF_PAGE_HDR_SIZE; if (!data_page) goto out; bpage = *data_page; if (!bpage) goto out; spin_lock_irqsave(&cpu_buffer->reader_lock, flags); reader = rb_get_reader_page(cpu_buffer); if (!reader) goto out_unlock; event = rb_reader_event(cpu_buffer); read = reader->read; commit = rb_page_commit(reader); /* * If this page has been partially read or * if len is not big enough to read the rest of the page or * a writer is still on the page, then * we must copy the data from the page to the buffer. * Otherwise, we can simply swap the page with the one passed in. */ if (read || (len < (commit - read)) || cpu_buffer->reader_page == cpu_buffer->commit_page) { struct buffer_data_page *rpage = cpu_buffer->reader_page->page; unsigned int rpos = read; unsigned int pos = 0; unsigned int size; if (full) goto out_unlock; if (len > (commit - read)) len = (commit - read); size = rb_event_length(event); if (len < size) goto out_unlock; /* save the current timestamp, since the user will need it */ save_timestamp = cpu_buffer->read_stamp; /* Need to copy one event at a time */ do { memcpy(bpage->data + pos, rpage->data + rpos, size); len -= size; rb_advance_reader(cpu_buffer); rpos = reader->read; pos += size; event = rb_reader_event(cpu_buffer); size = rb_event_length(event); } while (len > size); /* update bpage */ local_set(&bpage->commit, pos); bpage->time_stamp = save_timestamp; /* we copied everything to the beginning */ read = 0; } else { /* swap the pages */ rb_init_page(bpage); bpage = reader->page; reader->page = *data_page; local_set(&reader->write, 0); reader->read = 0; *data_page = bpage; /* update the entry counter */ rb_remove_entries(cpu_buffer, bpage, read); } ret = read; out_unlock: spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); out: return ret; } static ssize_t rb_simple_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) { unsigned long *p = filp->private_data; char buf[64]; int r; if (test_bit(RB_BUFFERS_DISABLED_BIT, p)) r = sprintf(buf, "permanently disabled\n"); else r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p)); return simple_read_from_buffer(ubuf, cnt, ppos, buf, r); } static ssize_t rb_simple_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) { unsigned long *p = filp->private_data; char buf[64]; unsigned long val; int ret; if (cnt >= sizeof(buf)) return -EINVAL; if (copy_from_user(&buf, ubuf, cnt)) return -EFAULT; buf[cnt] = 0; ret = strict_strtoul(buf, 10, &val); if (ret < 0) return ret; if (val) set_bit(RB_BUFFERS_ON_BIT, p); else clear_bit(RB_BUFFERS_ON_BIT, p); (*ppos)++; return cnt; } static const struct file_operations rb_simple_fops = { .open = tracing_open_generic, .read = rb_simple_read, .write = rb_simple_write, }; static __init int rb_init_debugfs(void) { struct dentry *d_tracer; struct dentry *entry; d_tracer = tracing_init_dentry(); entry = debugfs_create_file("tracing_on", 0644, d_tracer, &ring_buffer_flags, &rb_simple_fops); if (!entry) pr_warning("Could not create debugfs 'tracing_on' entry\n"); return 0; } fs_initcall(rb_init_debugfs); #ifdef CONFIG_HOTPLUG_CPU static int __cpuinit rb_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) { struct ring_buffer *buffer = container_of(self, struct ring_buffer, cpu_notify); long cpu = (long)hcpu; switch (action) { case CPU_UP_PREPARE: case CPU_UP_PREPARE_FROZEN: if (cpu_isset(cpu, *buffer->cpumask)) return NOTIFY_OK; buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, cpu); if (!buffer->buffers[cpu]) { WARN(1, "failed to allocate ring buffer on CPU %ld\n", cpu); return NOTIFY_OK; } smp_wmb(); cpu_set(cpu, *buffer->cpumask); break; case CPU_DOWN_PREPARE: case CPU_DOWN_PREPARE_FROZEN: /* * Do nothing. * If we were to free the buffer, then the user would * lose any trace that was in the buffer. */ break; default: break; } return NOTIFY_OK; } #endif