*/
#include <linux/delay.h>
-#include <linux/stop_machine.h>
#define RCU_KTHREAD_PRIO 1
printk(KERN_INFO "\tRCU torture testing starts during boot.\n");
#endif
#if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE)
- printk(KERN_INFO "\tVerbose stalled-CPUs detection is disabled.\n");
+ printk(KERN_INFO "\tDump stacks of tasks blocking RCU-preempt GP.\n");
+#endif
+#if defined(CONFIG_RCU_CPU_STALL_INFO)
+ printk(KERN_INFO "\tAdditional per-CPU info printed with stalls.\n");
#endif
#if NUM_RCU_LVL_4 != 0
printk(KERN_INFO "\tExperimental four-level hierarchy is enabled.\n");
#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */
+#ifdef CONFIG_RCU_CPU_STALL_INFO
+
+static void rcu_print_task_stall_begin(struct rcu_node *rnp)
+{
+ printk(KERN_ERR "\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
+ rnp->level, rnp->grplo, rnp->grphi);
+}
+
+static void rcu_print_task_stall_end(void)
+{
+ printk(KERN_CONT "\n");
+}
+
+#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
+
+static void rcu_print_task_stall_begin(struct rcu_node *rnp)
+{
+}
+
+static void rcu_print_task_stall_end(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */
+
/*
* Scan the current list of tasks blocked within RCU read-side critical
* sections, printing out the tid of each.
if (!rcu_preempt_blocked_readers_cgp(rnp))
return 0;
+ rcu_print_task_stall_begin(rnp);
t = list_entry(rnp->gp_tasks,
struct task_struct, rcu_node_entry);
list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
- printk(" P%d", t->pid);
+ printk(KERN_CONT " P%d", t->pid);
ndetected++;
}
+ rcu_print_task_stall_end();
return ndetected;
}
* absolutely necessary, but this is a good performance/complexity
* tradeoff.
*/
- if (rcu_preempt_blocked_readers_cgp(rnp))
+ if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0)
retval |= RCU_OFL_TASKS_NORM_GP;
if (rcu_preempted_readers_exp(rnp))
retval |= RCU_OFL_TASKS_EXP_GP;
rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */
}
-/*
- * Wait for an rcu-preempt grace period, but expedite it. The basic idea
- * is to invoke synchronize_sched_expedited() to push all the tasks to
- * the ->blkd_tasks lists and wait for this list to drain.
+/**
+ * synchronize_rcu_expedited - Brute-force RCU grace period
+ *
+ * Wait for an RCU-preempt grace period, but expedite it. The basic
+ * idea is to invoke synchronize_sched_expedited() to push all the tasks to
+ * the ->blkd_tasks lists and wait for this list to drain. This consumes
+ * significant time on all CPUs and is unfriendly to real-time workloads,
+ * so is thus not recommended for any sort of common-case code.
+ * In fact, if you are using synchronize_rcu_expedited() in a loop,
+ * please restructure your code to batch your updates, and then Use a
+ * single synchronize_rcu() instead.
+ *
+ * Note that it is illegal to call this function while holding any lock
+ * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
+ * to call this function from a CPU-hotplug notifier. Failing to observe
+ * these restriction will result in deadlock.
*/
void synchronize_rcu_expedited(void)
{
}
/*
- * Does preemptible RCU need the CPU to stay out of dynticks mode?
+ * Does preemptible RCU have callbacks on this CPU?
*/
-static int rcu_preempt_needs_cpu(int cpu)
+static int rcu_preempt_cpu_has_callbacks(int cpu)
{
return !!per_cpu(rcu_preempt_data, cpu).nxtlist;
}
}
/*
- * Because preemptible RCU does not exist, it never needs any CPU.
+ * Because preemptible RCU does not exist, it never has callbacks
*/
-static int rcu_preempt_needs_cpu(int cpu)
+static int rcu_preempt_cpu_has_callbacks(int cpu)
{
return 0;
}
#endif /* #else #ifdef CONFIG_RCU_BOOST */
-#ifndef CONFIG_SMP
-
-void synchronize_sched_expedited(void)
-{
- cond_resched();
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
-
-#else /* #ifndef CONFIG_SMP */
-
-static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0);
-static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0);
-
-static int synchronize_sched_expedited_cpu_stop(void *data)
-{
- /*
- * There must be a full memory barrier on each affected CPU
- * between the time that try_stop_cpus() is called and the
- * time that it returns.
- *
- * In the current initial implementation of cpu_stop, the
- * above condition is already met when the control reaches
- * this point and the following smp_mb() is not strictly
- * necessary. Do smp_mb() anyway for documentation and
- * robustness against future implementation changes.
- */
- smp_mb(); /* See above comment block. */
- return 0;
-}
-
-/*
- * Wait for an rcu-sched grace period to elapse, but use "big hammer"
- * approach to force grace period to end quickly. This consumes
- * significant time on all CPUs, and is thus not recommended for
- * any sort of common-case code.
- *
- * Note that it is illegal to call this function while holding any
- * lock that is acquired by a CPU-hotplug notifier. Failing to
- * observe this restriction will result in deadlock.
- *
- * This implementation can be thought of as an application of ticket
- * locking to RCU, with sync_sched_expedited_started and
- * sync_sched_expedited_done taking on the roles of the halves
- * of the ticket-lock word. Each task atomically increments
- * sync_sched_expedited_started upon entry, snapshotting the old value,
- * then attempts to stop all the CPUs. If this succeeds, then each
- * CPU will have executed a context switch, resulting in an RCU-sched
- * grace period. We are then done, so we use atomic_cmpxchg() to
- * update sync_sched_expedited_done to match our snapshot -- but
- * only if someone else has not already advanced past our snapshot.
- *
- * On the other hand, if try_stop_cpus() fails, we check the value
- * of sync_sched_expedited_done. If it has advanced past our
- * initial snapshot, then someone else must have forced a grace period
- * some time after we took our snapshot. In this case, our work is
- * done for us, and we can simply return. Otherwise, we try again,
- * but keep our initial snapshot for purposes of checking for someone
- * doing our work for us.
- *
- * If we fail too many times in a row, we fall back to synchronize_sched().
- */
-void synchronize_sched_expedited(void)
-{
- int firstsnap, s, snap, trycount = 0;
-
- /* Note that atomic_inc_return() implies full memory barrier. */
- firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
- get_online_cpus();
-
- /*
- * Each pass through the following loop attempts to force a
- * context switch on each CPU.
- */
- while (try_stop_cpus(cpu_online_mask,
- synchronize_sched_expedited_cpu_stop,
- NULL) == -EAGAIN) {
- put_online_cpus();
-
- /* No joy, try again later. Or just synchronize_sched(). */
- if (trycount++ < 10)
- udelay(trycount * num_online_cpus());
- else {
- synchronize_sched();
- return;
- }
-
- /* Check to see if someone else did our work for us. */
- s = atomic_read(&sync_sched_expedited_done);
- if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) {
- smp_mb(); /* ensure test happens before caller kfree */
- return;
- }
-
- /*
- * Refetching sync_sched_expedited_started allows later
- * callers to piggyback on our grace period. We subtract
- * 1 to get the same token that the last incrementer got.
- * We retry after they started, so our grace period works
- * for them, and they started after our first try, so their
- * grace period works for us.
- */
- get_online_cpus();
- snap = atomic_read(&sync_sched_expedited_started);
- smp_mb(); /* ensure read is before try_stop_cpus(). */
- }
-
- /*
- * Everyone up to our most recent fetch is covered by our grace
- * period. Update the counter, but only if our work is still
- * relevant -- which it won't be if someone who started later
- * than we did beat us to the punch.
- */
- do {
- s = atomic_read(&sync_sched_expedited_done);
- if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) {
- smp_mb(); /* ensure test happens before caller kfree */
- break;
- }
- } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s);
-
- put_online_cpus();
-}
-EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
-
-#endif /* #else #ifndef CONFIG_SMP */
-
#if !defined(CONFIG_RCU_FAST_NO_HZ)
/*
}
/*
- * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=y,
+ * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n,
* is nothing.
*/
static void rcu_prepare_for_idle(int cpu)
*/
static void rcu_prepare_for_idle(int cpu)
{
- unsigned long flags;
-
- local_irq_save(flags);
-
/*
* If there are no callbacks on this CPU, enter dyntick-idle mode.
* Also reset state to avoid prejudicing later attempts.
if (!rcu_cpu_has_callbacks(cpu)) {
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
per_cpu(rcu_dyntick_drain, cpu) = 0;
- local_irq_restore(flags);
trace_rcu_prep_idle("No callbacks");
return;
}
* refrained from disabling the scheduling-clock tick.
*/
if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies) {
- local_irq_restore(flags);
trace_rcu_prep_idle("In holdoff");
return;
}
/* First time through, initialize the counter. */
per_cpu(rcu_dyntick_drain, cpu) = RCU_IDLE_FLUSHES;
} else if (per_cpu(rcu_dyntick_drain, cpu) <= RCU_IDLE_OPT_FLUSHES &&
- !rcu_pending(cpu)) {
+ !rcu_pending(cpu) &&
+ !local_softirq_pending()) {
/* Can we go dyntick-idle despite still having callbacks? */
trace_rcu_prep_idle("Dyntick with callbacks");
per_cpu(rcu_dyntick_drain, cpu) = 0;
- per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
+ per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
if (rcu_cpu_has_nonlazy_callbacks(cpu))
hrtimer_start(&per_cpu(rcu_idle_gp_timer, cpu),
rcu_idle_gp_wait, HRTIMER_MODE_REL);
} else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
/* We have hit the limit, so time to give up. */
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
- local_irq_restore(flags);
trace_rcu_prep_idle("Begin holdoff");
invoke_rcu_core(); /* Force the CPU out of dyntick-idle. */
return;
*/
#ifdef CONFIG_TREE_PREEMPT_RCU
if (per_cpu(rcu_preempt_data, cpu).nxtlist) {
- local_irq_restore(flags);
rcu_preempt_qs(cpu);
force_quiescent_state(&rcu_preempt_state, 0);
- local_irq_save(flags);
}
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
if (per_cpu(rcu_sched_data, cpu).nxtlist) {
- local_irq_restore(flags);
rcu_sched_qs(cpu);
force_quiescent_state(&rcu_sched_state, 0);
- local_irq_save(flags);
}
if (per_cpu(rcu_bh_data, cpu).nxtlist) {
- local_irq_restore(flags);
rcu_bh_qs(cpu);
force_quiescent_state(&rcu_bh_state, 0);
- local_irq_save(flags);
}
/*
* So try forcing the callbacks through the grace period.
*/
if (rcu_cpu_has_callbacks(cpu)) {
- local_irq_restore(flags);
trace_rcu_prep_idle("More callbacks");
invoke_rcu_core();
- } else {
- local_irq_restore(flags);
+ } else
trace_rcu_prep_idle("Callbacks drained");
- }
}
#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
+
+#ifdef CONFIG_RCU_CPU_STALL_INFO
+
+#ifdef CONFIG_RCU_FAST_NO_HZ
+
+static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
+{
+ struct hrtimer *hrtp = &per_cpu(rcu_idle_gp_timer, cpu);
+
+ sprintf(cp, "drain=%d %c timer=%lld",
+ per_cpu(rcu_dyntick_drain, cpu),
+ per_cpu(rcu_dyntick_holdoff, cpu) == jiffies ? 'H' : '.',
+ hrtimer_active(hrtp)
+ ? ktime_to_us(hrtimer_get_remaining(hrtp))
+ : -1);
+}
+
+#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
+
+static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */
+
+/* Initiate the stall-info list. */
+static void print_cpu_stall_info_begin(void)
+{
+ printk(KERN_CONT "\n");
+}
+
+/*
+ * Print out diagnostic information for the specified stalled CPU.
+ *
+ * If the specified CPU is aware of the current RCU grace period
+ * (flavor specified by rsp), then print the number of scheduling
+ * clock interrupts the CPU has taken during the time that it has
+ * been aware. Otherwise, print the number of RCU grace periods
+ * that this CPU is ignorant of, for example, "1" if the CPU was
+ * aware of the previous grace period.
+ *
+ * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info.
+ */
+static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
+{
+ char fast_no_hz[72];
+ struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
+ struct rcu_dynticks *rdtp = rdp->dynticks;
+ char *ticks_title;
+ unsigned long ticks_value;
+
+ if (rsp->gpnum == rdp->gpnum) {
+ ticks_title = "ticks this GP";
+ ticks_value = rdp->ticks_this_gp;
+ } else {
+ ticks_title = "GPs behind";
+ ticks_value = rsp->gpnum - rdp->gpnum;
+ }
+ print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
+ printk(KERN_ERR "\t%d: (%lu %s) idle=%03x/%llx/%d %s\n",
+ cpu, ticks_value, ticks_title,
+ atomic_read(&rdtp->dynticks) & 0xfff,
+ rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,
+ fast_no_hz);
+}
+
+/* Terminate the stall-info list. */
+static void print_cpu_stall_info_end(void)
+{
+ printk(KERN_ERR "\t");
+}
+
+/* Zero ->ticks_this_gp for all flavors of RCU. */
+static void zero_cpu_stall_ticks(struct rcu_data *rdp)
+{
+ rdp->ticks_this_gp = 0;
+}
+
+/* Increment ->ticks_this_gp for all flavors of RCU. */
+static void increment_cpu_stall_ticks(void)
+{
+ __get_cpu_var(rcu_sched_data).ticks_this_gp++;
+ __get_cpu_var(rcu_bh_data).ticks_this_gp++;
+#ifdef CONFIG_TREE_PREEMPT_RCU
+ __get_cpu_var(rcu_preempt_data).ticks_this_gp++;
+#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+}
+
+#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
+
+static void print_cpu_stall_info_begin(void)
+{
+ printk(KERN_CONT " {");
+}
+
+static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
+{
+ printk(KERN_CONT " %d", cpu);
+}
+
+static void print_cpu_stall_info_end(void)
+{
+ printk(KERN_CONT "} ");
+}
+
+static void zero_cpu_stall_ticks(struct rcu_data *rdp)
+{
+}
+
+static void increment_cpu_stall_ticks(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */
projects / linux-flexiantxendom0-3.2.10.git / blobdiff