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rcu: Deconfuse dynticks entry-exit tracing
The trace_rcu_dyntick() trace event did not print both the old and the new value of the nesting level, and furthermore printed only the low-order 32 bits of it. This could result in some confusion when interpreting trace-event dumps, so this commit prints both the old and the new value, prints the full 64 bits, and also selects the process-entry/exit increment to print nicely in hexadecimal. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney
Paul E. McKenney
parent
9ceae0e248
commit
4145fa7fbe
@ -246,21 +246,24 @@ TRACE_EVENT(rcu_fqs,
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*/
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TRACE_EVENT(rcu_dyntick,
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TP_PROTO(char *polarity, int nesting),
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TP_PROTO(char *polarity, long long oldnesting, long long newnesting),
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TP_ARGS(polarity, nesting),
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TP_ARGS(polarity, oldnesting, newnesting),
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TP_STRUCT__entry(
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__field(char *, polarity)
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__field(int, nesting)
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__field(long long, oldnesting)
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__field(long long, newnesting)
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),
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TP_fast_assign(
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__entry->polarity = polarity;
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__entry->nesting = nesting;
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__entry->oldnesting = oldnesting;
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__entry->newnesting = newnesting;
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),
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TP_printk("%s %d", __entry->polarity, __entry->nesting)
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TP_printk("%s %llx %llx", __entry->polarity,
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__entry->oldnesting, __entry->newnesting)
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);
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/*
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@ -470,7 +473,7 @@ TRACE_EVENT(rcu_torture_read,
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#define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
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#define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, grplo, grphi, gp_tasks) do { } while (0)
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#define trace_rcu_fqs(rcuname, gpnum, cpu, qsevent) do { } while (0)
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#define trace_rcu_dyntick(polarity, nesting) do { } while (0)
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#define trace_rcu_dyntick(polarity, oldnesting, newnesting) do { } while (0)
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#define trace_rcu_callback(rcuname, rhp, qlen) do { } while (0)
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#define trace_rcu_kfree_callback(rcuname, rhp, offset, qlen) do { } while (0)
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#define trace_rcu_batch_start(rcuname, qlen, blimit) do { } while (0)
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@ -29,6 +29,13 @@
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#define RCU_TRACE(stmt)
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#endif /* #else #ifdef CONFIG_RCU_TRACE */
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/*
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* Process-level increment to ->dynticks_nesting field. This allows for
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* architectures that use half-interrupts and half-exceptions from
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* process context.
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*/
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#define DYNTICK_TASK_NESTING (LLONG_MAX / 2 - 1)
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/*
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* debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
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* by call_rcu() and rcu callback execution, and are therefore not part of the
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@ -53,20 +53,21 @@ static void __call_rcu(struct rcu_head *head,
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#include "rcutiny_plugin.h"
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static long long rcu_dynticks_nesting = LLONG_MAX / 2;
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static long long rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
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/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
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static void rcu_idle_enter_common(void)
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static void rcu_idle_enter_common(long long oldval)
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{
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if (rcu_dynticks_nesting) {
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RCU_TRACE(trace_rcu_dyntick("--=", rcu_dynticks_nesting));
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RCU_TRACE(trace_rcu_dyntick("--=",
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oldval, rcu_dynticks_nesting));
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return;
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}
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RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting));
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RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
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if (!idle_cpu(smp_processor_id())) {
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WARN_ON_ONCE(1); /* must be idle task! */
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RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
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rcu_dynticks_nesting));
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oldval, rcu_dynticks_nesting));
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ftrace_dump(DUMP_ALL);
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}
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rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
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@ -79,10 +80,12 @@ static void rcu_idle_enter_common(void)
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void rcu_idle_enter(void)
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{
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unsigned long flags;
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long long oldval;
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local_irq_save(flags);
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oldval = rcu_dynticks_nesting;
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rcu_dynticks_nesting = 0;
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rcu_idle_enter_common();
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rcu_idle_enter_common(oldval);
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local_irq_restore(flags);
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}
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@ -92,11 +95,13 @@ void rcu_idle_enter(void)
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void rcu_irq_exit(void)
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{
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unsigned long flags;
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long long oldval;
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local_irq_save(flags);
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oldval = rcu_dynticks_nesting;
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rcu_dynticks_nesting--;
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WARN_ON_ONCE(rcu_dynticks_nesting < 0);
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rcu_idle_enter_common();
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rcu_idle_enter_common(oldval);
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local_irq_restore(flags);
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}
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@ -104,14 +109,15 @@ void rcu_irq_exit(void)
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static void rcu_idle_exit_common(long long oldval)
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{
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if (oldval) {
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RCU_TRACE(trace_rcu_dyntick("++=", rcu_dynticks_nesting));
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RCU_TRACE(trace_rcu_dyntick("++=",
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oldval, rcu_dynticks_nesting));
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return;
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}
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RCU_TRACE(trace_rcu_dyntick("End", oldval));
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RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
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if (!idle_cpu(smp_processor_id())) {
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WARN_ON_ONCE(1); /* must be idle task! */
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RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
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oldval));
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oldval, rcu_dynticks_nesting));
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ftrace_dump(DUMP_ALL);
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}
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}
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@ -127,7 +133,7 @@ void rcu_idle_exit(void)
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local_irq_save(flags);
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oldval = rcu_dynticks_nesting;
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WARN_ON_ONCE(oldval != 0);
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rcu_dynticks_nesting = LLONG_MAX / 2;
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rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
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rcu_idle_exit_common(oldval);
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local_irq_restore(flags);
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}
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@ -196,7 +196,7 @@ void rcu_note_context_switch(int cpu)
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EXPORT_SYMBOL_GPL(rcu_note_context_switch);
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DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
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.dynticks_nesting = LLONG_MAX / 2,
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.dynticks_nesting = DYNTICK_TASK_NESTING,
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.dynticks = ATOMIC_INIT(1),
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};
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@ -348,17 +348,17 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
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* we really have entered idle, and must do the appropriate accounting.
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* The caller must have disabled interrupts.
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*/
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static void rcu_idle_enter_common(struct rcu_dynticks *rdtp)
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static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
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{
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if (rdtp->dynticks_nesting) {
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trace_rcu_dyntick("--=", rdtp->dynticks_nesting);
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trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);
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return;
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}
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trace_rcu_dyntick("Start", rdtp->dynticks_nesting);
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trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
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if (!idle_cpu(smp_processor_id())) {
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WARN_ON_ONCE(1); /* must be idle task! */
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trace_rcu_dyntick("Error on entry: not idle task",
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rdtp->dynticks_nesting);
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oldval, rdtp->dynticks_nesting);
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ftrace_dump(DUMP_ALL);
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}
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/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
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@ -383,12 +383,14 @@ static void rcu_idle_enter_common(struct rcu_dynticks *rdtp)
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void rcu_idle_enter(void)
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{
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unsigned long flags;
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long long oldval;
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struct rcu_dynticks *rdtp;
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local_irq_save(flags);
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rdtp = &__get_cpu_var(rcu_dynticks);
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oldval = rdtp->dynticks_nesting;
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rdtp->dynticks_nesting = 0;
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rcu_idle_enter_common(rdtp);
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rcu_idle_enter_common(rdtp, oldval);
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local_irq_restore(flags);
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}
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@ -411,13 +413,15 @@ void rcu_idle_enter(void)
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void rcu_irq_exit(void)
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{
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unsigned long flags;
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long long oldval;
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struct rcu_dynticks *rdtp;
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local_irq_save(flags);
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rdtp = &__get_cpu_var(rcu_dynticks);
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oldval = rdtp->dynticks_nesting;
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rdtp->dynticks_nesting--;
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WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
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rcu_idle_enter_common(rdtp);
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rcu_idle_enter_common(rdtp, oldval);
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local_irq_restore(flags);
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}
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@ -431,7 +435,7 @@ void rcu_irq_exit(void)
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static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
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{
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if (oldval) {
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trace_rcu_dyntick("++=", rdtp->dynticks_nesting);
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trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting);
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return;
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}
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smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
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@ -439,10 +443,11 @@ static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
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/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
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smp_mb__after_atomic_inc(); /* See above. */
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WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
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trace_rcu_dyntick("End", oldval);
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trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
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if (!idle_cpu(smp_processor_id())) {
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WARN_ON_ONCE(1); /* must be idle task! */
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trace_rcu_dyntick("Error on exit: not idle task", oldval);
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trace_rcu_dyntick("Error on exit: not idle task",
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oldval, rdtp->dynticks_nesting);
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ftrace_dump(DUMP_ALL);
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}
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}
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@ -453,8 +458,8 @@ static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
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* Exit idle mode, in other words, -enter- the mode in which RCU
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* read-side critical sections can occur.
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*
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* We crowbar the ->dynticks_nesting field to LLONG_MAX/2 to allow for
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* the possibility of usermode upcalls messing up our count
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* We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NESTING to
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* allow for the possibility of usermode upcalls messing up our count
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* of interrupt nesting level during the busy period that is just
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* now starting.
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*/
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@ -468,7 +473,7 @@ void rcu_idle_exit(void)
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rdtp = &__get_cpu_var(rcu_dynticks);
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oldval = rdtp->dynticks_nesting;
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WARN_ON_ONCE(oldval != 0);
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rdtp->dynticks_nesting = LLONG_MAX / 2;
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rdtp->dynticks_nesting = DYNTICK_TASK_NESTING;
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rcu_idle_exit_common(rdtp, oldval);
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local_irq_restore(flags);
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}
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@ -2012,7 +2017,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
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rdp->nxttail[i] = &rdp->nxtlist;
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rdp->qlen = 0;
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rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
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WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);
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WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_NESTING);
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WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
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rdp->cpu = cpu;
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rdp->rsp = rsp;
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@ -2040,7 +2045,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
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rdp->qlen_last_fqs_check = 0;
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rdp->n_force_qs_snap = rsp->n_force_qs;
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rdp->blimit = blimit;
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WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);
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WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_NESTING);
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WARN_ON_ONCE((atomic_read(&rdp->dynticks->dynticks) & 0x1) != 1);
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raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
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