HACK: ARM: disable sleeping while atomic warning in do_signal
[linux-2.6.git] / kernel / rcutiny.c
index 0c343b9..37a5444 100644 (file)
  * For detailed explanation of Read-Copy Update mechanism see -
  *             Documentation/RCU
  */
-#include <linux/moduleparam.h>
 #include <linux/completion.h>
 #include <linux/interrupt.h>
 #include <linux/notifier.h>
 #include <linux/rcupdate.h>
 #include <linux/kernel.h>
-#include <linux/module.h>
+#include <linux/export.h>
 #include <linux/mutex.h>
 #include <linux/sched.h>
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/time.h>
 #include <linux/cpu.h>
+#include <linux/prefetch.h>
 
-/* Controls for rcu_kthread() kthread, replacing RCU_SOFTIRQ used previously. */
-static struct task_struct *rcu_kthread_task;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
-static unsigned long have_rcu_kthread_work;
-static void invoke_rcu_kthread(void);
+#ifdef CONFIG_RCU_TRACE
+#include <trace/events/rcu.h>
+#endif /* #else #ifdef CONFIG_RCU_TRACE */
+
+#include "rcu.h"
 
 /* Forward declarations for rcutiny_plugin.h. */
 struct rcu_ctrlblk;
-static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
-static int rcu_kthread(void *arg);
+static void invoke_rcu_callbacks(void);
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
+static void rcu_process_callbacks(struct softirq_action *unused);
 static void __call_rcu(struct rcu_head *head,
                       void (*func)(struct rcu_head *rcu),
                       struct rcu_ctrlblk *rcp);
 
 #include "rcutiny_plugin.h"
 
-#ifdef CONFIG_NO_HZ
+static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
 
-static long rcu_dynticks_nesting = 1;
+/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
+static void rcu_idle_enter_common(long long oldval)
+{
+       if (rcu_dynticks_nesting) {
+               RCU_TRACE(trace_rcu_dyntick("--=",
+                                           oldval, rcu_dynticks_nesting));
+               return;
+       }
+       RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
+       if (!is_idle_task(current)) {
+               struct task_struct *idle = idle_task(smp_processor_id());
+
+               RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
+                                           oldval, rcu_dynticks_nesting));
+               ftrace_dump(DUMP_ALL);
+               WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                         current->pid, current->comm,
+                         idle->pid, idle->comm); /* must be idle task! */
+       }
+       rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+}
 
 /*
- * Enter dynticks-idle mode, which is an extended quiescent state
- * if we have fully entered that mode (i.e., if the new value of
- * dynticks_nesting is zero).
+ * Enter idle, which is an extended quiescent state if we have fully
+ * entered that mode (i.e., if the new value of dynticks_nesting is zero).
  */
-void rcu_enter_nohz(void)
+void rcu_idle_enter(void)
 {
-       if (--rcu_dynticks_nesting == 0)
-               rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
+       unsigned long flags;
+       long long oldval;
+
+       local_irq_save(flags);
+       oldval = rcu_dynticks_nesting;
+       WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0);
+       if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) ==
+           DYNTICK_TASK_NEST_VALUE)
+               rcu_dynticks_nesting = 0;
+       else
+               rcu_dynticks_nesting  -= DYNTICK_TASK_NEST_VALUE;
+       rcu_idle_enter_common(oldval);
+       local_irq_restore(flags);
 }
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
 
 /*
- * Exit dynticks-idle mode, so that we are no longer in an extended
- * quiescent state.
+ * Exit an interrupt handler towards idle.
  */
-void rcu_exit_nohz(void)
+void rcu_irq_exit(void)
 {
-       rcu_dynticks_nesting++;
+       unsigned long flags;
+       long long oldval;
+
+       local_irq_save(flags);
+       oldval = rcu_dynticks_nesting;
+       rcu_dynticks_nesting--;
+       WARN_ON_ONCE(rcu_dynticks_nesting < 0);
+       rcu_idle_enter_common(oldval);
+       local_irq_restore(flags);
 }
 
-#endif /* #ifdef CONFIG_NO_HZ */
+/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
+static void rcu_idle_exit_common(long long oldval)
+{
+       if (oldval) {
+               RCU_TRACE(trace_rcu_dyntick("++=",
+                                           oldval, rcu_dynticks_nesting));
+               return;
+       }
+       RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
+       if (!is_idle_task(current)) {
+               struct task_struct *idle = idle_task(smp_processor_id());
+
+               RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
+                         oldval, rcu_dynticks_nesting));
+               ftrace_dump(DUMP_ALL);
+               WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+                         current->pid, current->comm,
+                         idle->pid, idle->comm); /* must be idle task! */
+       }
+}
 
 /*
- * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
- * Also disable irqs to avoid confusion due to interrupt handlers
- * invoking call_rcu().
+ * Exit idle, so that we are no longer in an extended quiescent state.
  */
-static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+void rcu_idle_exit(void)
 {
        unsigned long flags;
+       long long oldval;
 
        local_irq_save(flags);
+       oldval = rcu_dynticks_nesting;
+       WARN_ON_ONCE(rcu_dynticks_nesting < 0);
+       if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK)
+               rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
+       else
+               rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+       rcu_idle_exit_common(oldval);
+       local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
+
+/*
+ * Enter an interrupt handler, moving away from idle.
+ */
+void rcu_irq_enter(void)
+{
+       unsigned long flags;
+       long long oldval;
+
+       local_irq_save(flags);
+       oldval = rcu_dynticks_nesting;
+       rcu_dynticks_nesting++;
+       WARN_ON_ONCE(rcu_dynticks_nesting == 0);
+       rcu_idle_exit_common(oldval);
+       local_irq_restore(flags);
+}
+
+#ifdef CONFIG_PROVE_RCU
+
+/*
+ * Test whether RCU thinks that the current CPU is idle.
+ */
+int rcu_is_cpu_idle(void)
+{
+       return !rcu_dynticks_nesting;
+}
+EXPORT_SYMBOL(rcu_is_cpu_idle);
+
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
+/*
+ * Test whether the current CPU was interrupted from idle.  Nested
+ * interrupts don't count, we must be running at the first interrupt
+ * level.
+ */
+int rcu_is_cpu_rrupt_from_idle(void)
+{
+       return rcu_dynticks_nesting <= 0;
+}
+
+/*
+ * Helper function for rcu_sched_qs() and rcu_bh_qs().
+ * Also irqs are disabled to avoid confusion due to interrupt handlers
+ * invoking call_rcu().
+ */
+static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+{
        if (rcp->rcucblist != NULL &&
            rcp->donetail != rcp->curtail) {
                rcp->donetail = rcp->curtail;
-               local_irq_restore(flags);
                return 1;
        }
-       local_irq_restore(flags);
 
        return 0;
 }
@@ -106,9 +218,13 @@ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
  */
 void rcu_sched_qs(int cpu)
 {
+       unsigned long flags;
+
+       local_irq_save(flags);
        if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
            rcu_qsctr_help(&rcu_bh_ctrlblk))
-               invoke_rcu_kthread();
+               invoke_rcu_callbacks();
+       local_irq_restore(flags);
 }
 
 /*
@@ -116,20 +232,23 @@ void rcu_sched_qs(int cpu)
  */
 void rcu_bh_qs(int cpu)
 {
+       unsigned long flags;
+
+       local_irq_save(flags);
        if (rcu_qsctr_help(&rcu_bh_ctrlblk))
-               invoke_rcu_kthread();
+               invoke_rcu_callbacks();
+       local_irq_restore(flags);
 }
 
 /*
  * Check to see if the scheduling-clock interrupt came from an extended
- * quiescent state, and, if so, tell RCU about it.
+ * quiescent state, and, if so, tell RCU about it.  This function must
+ * be called from hardirq context.  It is normally called from the
+ * scheduling-clock interrupt.
  */
 void rcu_check_callbacks(int cpu, int user)
 {
-       if (user ||
-           (idle_cpu(cpu) &&
-            !in_softirq() &&
-            hardirq_count() <= (1 << HARDIRQ_SHIFT)))
+       if (user || rcu_is_cpu_rrupt_from_idle())
                rcu_sched_qs(cpu);
        else if (!in_softirq())
                rcu_bh_qs(cpu);
@@ -140,18 +259,27 @@ void rcu_check_callbacks(int cpu, int user)
  * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
  * whose grace period has elapsed.
  */
-static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
+static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 {
+       char *rn = NULL;
        struct rcu_head *next, *list;
        unsigned long flags;
        RCU_TRACE(int cb_count = 0);
 
        /* If no RCU callbacks ready to invoke, just return. */
-       if (&rcp->rcucblist == rcp->donetail)
+       if (&rcp->rcucblist == rcp->donetail) {
+               RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1));
+               RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,
+                                             ACCESS_ONCE(rcp->rcucblist),
+                                             need_resched(),
+                                             is_idle_task(current),
+                                             rcu_is_callbacks_kthread()));
                return;
+       }
 
        /* Move the ready-to-invoke callbacks to a local list. */
        local_irq_save(flags);
+       RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1));
        list = rcp->rcucblist;
        rcp->rcucblist = *rcp->donetail;
        *rcp->donetail = NULL;
@@ -162,63 +290,28 @@ static void rcu_process_callbacks(struct rcu_ctrlblk *rcp)
        local_irq_restore(flags);
 
        /* Invoke the callbacks on the local list. */
+       RCU_TRACE(rn = rcp->name);
        while (list) {
                next = list->next;
                prefetch(next);
                debug_rcu_head_unqueue(list);
                local_bh_disable();
-               list->func(list);
+               __rcu_reclaim(rn, list);
                local_bh_enable();
                list = next;
                RCU_TRACE(cb_count++);
        }
        RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
+       RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(),
+                                     is_idle_task(current),
+                                     rcu_is_callbacks_kthread()));
 }
 
-/*
- * This kthread invokes RCU callbacks whose grace periods have
- * elapsed.  It is awakened as needed, and takes the place of the
- * RCU_SOFTIRQ that was used previously for this purpose.
- * This is a kthread, but it is never stopped, at least not until
- * the system goes down.
- */
-static int rcu_kthread(void *arg)
+static void rcu_process_callbacks(struct softirq_action *unused)
 {
-       unsigned long work;
-       unsigned long morework;
-       unsigned long flags;
-
-       for (;;) {
-               wait_event_interruptible(rcu_kthread_wq,
-                                        have_rcu_kthread_work != 0);
-               morework = rcu_boost();
-               local_irq_save(flags);
-               work = have_rcu_kthread_work;
-               have_rcu_kthread_work = morework;
-               local_irq_restore(flags);
-               if (work) {
-                       rcu_process_callbacks(&rcu_sched_ctrlblk);
-                       rcu_process_callbacks(&rcu_bh_ctrlblk);
-                       rcu_preempt_process_callbacks();
-               }
-               schedule_timeout_interruptible(1); /* Leave CPU for others. */
-       }
-
-       return 0;  /* Not reached, but needed to shut gcc up. */
-}
-
-/*
- * Wake up rcu_kthread() to process callbacks now eligible for invocation
- * or to boost readers.
- */
-static void invoke_rcu_kthread(void)
-{
-       unsigned long flags;
-
-       local_irq_save(flags);
-       have_rcu_kthread_work = 1;
-       wake_up(&rcu_kthread_wq);
-       local_irq_restore(flags);
+       __rcu_process_callbacks(&rcu_sched_ctrlblk);
+       __rcu_process_callbacks(&rcu_bh_ctrlblk);
+       rcu_preempt_process_callbacks();
 }
 
 /*
@@ -236,6 +329,10 @@ static void invoke_rcu_kthread(void)
  */
 void synchronize_sched(void)
 {
+       rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                          !lock_is_held(&rcu_lock_map) &&
+                          !lock_is_held(&rcu_sched_lock_map),
+                          "Illegal synchronize_sched() in RCU read-side critical section");
        cond_resched();
 }
 EXPORT_SYMBOL_GPL(synchronize_sched);
@@ -280,45 +377,3 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
        __call_rcu(head, func, &rcu_bh_ctrlblk);
 }
 EXPORT_SYMBOL_GPL(call_rcu_bh);
-
-void rcu_barrier_bh(void)
-{
-       struct rcu_synchronize rcu;
-
-       init_rcu_head_on_stack(&rcu.head);
-       init_completion(&rcu.completion);
-       /* Will wake me after RCU finished. */
-       call_rcu_bh(&rcu.head, wakeme_after_rcu);
-       /* Wait for it. */
-       wait_for_completion(&rcu.completion);
-       destroy_rcu_head_on_stack(&rcu.head);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_bh);
-
-void rcu_barrier_sched(void)
-{
-       struct rcu_synchronize rcu;
-
-       init_rcu_head_on_stack(&rcu.head);
-       init_completion(&rcu.completion);
-       /* Will wake me after RCU finished. */
-       call_rcu_sched(&rcu.head, wakeme_after_rcu);
-       /* Wait for it. */
-       wait_for_completion(&rcu.completion);
-       destroy_rcu_head_on_stack(&rcu.head);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_sched);
-
-/*
- * Spawn the kthread that invokes RCU callbacks.
- */
-static int __init rcu_spawn_kthreads(void)
-{
-       struct sched_param sp;
-
-       rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
-       sp.sched_priority = RCU_BOOST_PRIO;
-       sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
-       return 0;
-}
-early_initcall(rcu_spawn_kthreads);