HACK: ARM: disable sleeping while atomic warning in do_signal
[linux-2.6.git] / kernel / rcutiny.c
index 0b54efd..37a5444 100644 (file)
  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  *
  * For detailed explanation of Read-Copy Update mechanism see -
- *             Documentation/RCU
+ *             Documentation/RCU
  */
-
-#include <linux/types.h>
-#include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/rcupdate.h>
-#include <linux/interrupt.h>
-#include <linux/sched.h>
-#include <linux/module.h>
 #include <linux/completion.h>
-#include <linux/moduleparam.h>
+#include <linux/interrupt.h>
 #include <linux/notifier.h>
-#include <linux/cpu.h>
+#include <linux/rcupdate.h>
+#include <linux/kernel.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>
+
+#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 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"
 
-/* Global control variables for rcupdate callback mechanism. */
-struct rcu_ctrlblk {
-       struct rcu_head *rcucblist;     /* List of pending callbacks (CBs). */
-       struct rcu_head **donetail;     /* ->next pointer of last "done" CB. */
-       struct rcu_head **curtail;      /* ->next pointer of last CB. */
-};
-
-/* Definition for rcupdate control block. */
-static struct rcu_ctrlblk rcu_ctrlblk = {
-       .rcucblist = NULL,
-       .donetail = &rcu_ctrlblk.rcucblist,
-       .curtail = &rcu_ctrlblk.rcucblist,
-};
-static struct rcu_ctrlblk rcu_bh_ctrlblk = {
-       .rcucblist = NULL,
-       .donetail = &rcu_bh_ctrlblk.rcucblist,
-       .curtail = &rcu_bh_ctrlblk.rcucblist,
-};
-
-#ifdef CONFIG_NO_HZ
-
-static long rcu_dynticks_nesting = 1;
+static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+
+/* 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);
+}
+
+/* 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! */
+       }
 }
 
-#endif /* #ifdef CONFIG_NO_HZ */
+/*
+ * Exit idle, so that we are no longer in an extended quiescent state.
+ */
+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);
 
 /*
- * Helper function for rcu_qsctr_inc() and rcu_bh_qsctr_inc().
- * Also disable irqs to avoid confusion due to interrupt handlers invoking
- * call_rcu().
+ * Enter an interrupt handler, moving away from idle.
  */
-static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
+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;
 }
 
@@ -109,8 +218,13 @@ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
  */
 void rcu_sched_qs(int cpu)
 {
-       if (rcu_qsctr_help(&rcu_ctrlblk) + rcu_qsctr_help(&rcu_bh_ctrlblk))
-               raise_softirq(RCU_SOFTIRQ);
+       unsigned long flags;
+
+       local_irq_save(flags);
+       if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
+           rcu_qsctr_help(&rcu_bh_ctrlblk))
+               invoke_rcu_callbacks();
+       local_irq_restore(flags);
 }
 
 /*
@@ -118,74 +232,86 @@ 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))
-               raise_softirq(RCU_SOFTIRQ);
+               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);
+       rcu_preempt_check_callbacks();
 }
 
 /*
- * Helper function for rcu_process_callbacks() that operates on the
- * specified rcu_ctrlkblk structure.
+ * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
+ * whose grace period has elapsed.
  */
 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
 {
-       unsigned long flags;
+       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;
        if (rcp->curtail == rcp->donetail)
                rcp->curtail = &rcp->rcucblist;
+       rcu_preempt_remove_callbacks(rcp);
        rcp->donetail = &rcp->rcucblist;
        local_irq_restore(flags);
 
        /* Invoke the callbacks on the local list. */
+       RCU_TRACE(rn = rcp->name);
        while (list) {
                next = list->next;
                prefetch(next);
-               list->func(list);
+               debug_rcu_head_unqueue(list);
+               local_bh_disable();
+               __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()));
 }
 
-/*
- * Invoke any callbacks whose grace period has completed.
- */
 static void rcu_process_callbacks(struct softirq_action *unused)
 {
-       __rcu_process_callbacks(&rcu_ctrlblk);
+       __rcu_process_callbacks(&rcu_sched_ctrlblk);
        __rcu_process_callbacks(&rcu_bh_ctrlblk);
-}
-
-/*
- * Null function to handle CPU being onlined.  Longer term, we want to
- * make TINY_RCU avoid using rcupdate.c, but later...
- */
-int rcu_cpu_notify(struct notifier_block *self,
-                  unsigned long action, void *hcpu)
-{
-       return NOTIFY_OK;
+       rcu_preempt_process_callbacks();
 }
 
 /*
@@ -198,20 +324,19 @@ int rcu_cpu_notify(struct notifier_block *self,
  *
  * Cool, huh?  (Due to Josh Triplett.)
  *
- * But we want to make this a static inline later.
+ * But we want to make this a static inline later.  The cond_resched()
+ * currently makes this problematic.
  */
 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);
 
-void synchronize_rcu_bh(void)
-{
-       synchronize_sched();
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
-
 /*
  * Helper function for call_rcu() and call_rcu_bh().
  */
@@ -221,74 +346,34 @@ static void __call_rcu(struct rcu_head *head,
 {
        unsigned long flags;
 
+       debug_rcu_head_queue(head);
        head->func = func;
        head->next = NULL;
+
        local_irq_save(flags);
        *rcp->curtail = head;
        rcp->curtail = &head->next;
+       RCU_TRACE(rcp->qlen++);
        local_irq_restore(flags);
 }
 
 /*
- * Post an RCU callback to be invoked after the end of an RCU grace
+ * Post an RCU callback to be invoked after the end of an RCU-sched grace
  * period.  But since we have but one CPU, that would be after any
  * quiescent state.
  */
-void call_rcu(struct rcu_head *head,
-             void (*func)(struct rcu_head *rcu))
+void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 {
-       __call_rcu(head, func, &rcu_ctrlblk);
+       __call_rcu(head, func, &rcu_sched_ctrlblk);
 }
-EXPORT_SYMBOL_GPL(call_rcu);
+EXPORT_SYMBOL_GPL(call_rcu_sched);
 
 /*
  * Post an RCU bottom-half callback to be invoked after any subsequent
  * quiescent state.
  */
-void call_rcu_bh(struct rcu_head *head,
-                void (*func)(struct rcu_head *rcu))
+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(void)
-{
-       struct rcu_synchronize rcu;
-
-       init_completion(&rcu.completion);
-       /* Will wake me after RCU finished. */
-       call_rcu(&rcu.head, wakeme_after_rcu);
-       /* Wait for it. */
-       wait_for_completion(&rcu.completion);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier);
-
-void rcu_barrier_bh(void)
-{
-       struct rcu_synchronize rcu;
-
-       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);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_bh);
-
-void rcu_barrier_sched(void)
-{
-       struct rcu_synchronize rcu;
-
-       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);
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_sched);
-
-void __rcu_init(void)
-{
-       open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
-}