Commit 4145fa7f authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 9ceae0e2

include/trace/events/rcu.h

+9 −6
Original line number Diff line number Diff line
@@ -246,21 +246,24 @@ TRACE_EVENT(rcu_fqs, 
 */

TRACE_EVENT(rcu_dyntick,



	TP_PROTO(char *polarity, int nesting),

	TP_PROTO(char *polarity, long long oldnesting, long long newnesting),



	TP_ARGS(polarity, nesting),

	TP_ARGS(polarity, oldnesting, newnesting),



	TP_STRUCT__entry(

		__field(char *, polarity)

		__field(int, nesting)

		__field(long long, oldnesting)

		__field(long long, newnesting)

	),



	TP_fast_assign(

		__entry->polarity = polarity;

		__entry->nesting = nesting;

		__entry->oldnesting = oldnesting;

		__entry->newnesting = newnesting;

	),



	TP_printk("%s %d", __entry->polarity, __entry->nesting)

	TP_printk("%s %llx %llx", __entry->polarity,

		  __entry->oldnesting, __entry->newnesting)

);



/*
@@ -470,7 +473,7 @@ TRACE_EVENT(rcu_torture_read, 
#define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)

#define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, grplo, grphi, gp_tasks) do { } while (0)

#define trace_rcu_fqs(rcuname, gpnum, cpu, qsevent) do { } while (0)

#define trace_rcu_dyntick(polarity, nesting) do { } while (0)

#define trace_rcu_dyntick(polarity, oldnesting, newnesting) do { } while (0)

#define trace_rcu_callback(rcuname, rhp, qlen) do { } while (0)

#define trace_rcu_kfree_callback(rcuname, rhp, offset, qlen) do { } while (0)

#define trace_rcu_batch_start(rcuname, qlen, blimit) do { } while (0)

kernel/rcu.h

+7 −0
Original line number Diff line number Diff line
@@ -29,6 +29,13 @@ 
#define RCU_TRACE(stmt)

#endif /* #else #ifdef CONFIG_RCU_TRACE */



/*

 * Process-level increment to ->dynticks_nesting field.  This allows for

 * architectures that use half-interrupts and half-exceptions from

 * process context.

 */

#define DYNTICK_TASK_NESTING (LLONG_MAX / 2 - 1)



/*

 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally

 * by call_rcu() and rcu callback execution, and are therefore not part of the

kernel/rcutiny.c

+17 −11
Original line number Diff line number Diff line
@@ -53,20 +53,21 @@ static void __call_rcu(struct rcu_head *head, 


#include "rcutiny_plugin.h"



static long long rcu_dynticks_nesting = LLONG_MAX / 2;

static long long rcu_dynticks_nesting = DYNTICK_TASK_NESTING;



/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */

static void rcu_idle_enter_common(void)

static void rcu_idle_enter_common(long long oldval)

{

	if (rcu_dynticks_nesting) {

		RCU_TRACE(trace_rcu_dyntick("--=", rcu_dynticks_nesting));

		RCU_TRACE(trace_rcu_dyntick("--=",

					    oldval, rcu_dynticks_nesting));

		return;

	}

	RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting));

	RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));

	if (!idle_cpu(smp_processor_id())) {

		WARN_ON_ONCE(1);	/* must be idle task! */

		RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",

					    rcu_dynticks_nesting));

					    oldval, rcu_dynticks_nesting));

		ftrace_dump(DUMP_ALL);

	}

	rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
@@ -79,10 +80,12 @@ static void rcu_idle_enter_common(void) 
void rcu_idle_enter(void)

{

	unsigned long flags;

	long long oldval;



	local_irq_save(flags);

	oldval = rcu_dynticks_nesting;

	rcu_dynticks_nesting = 0;

	rcu_idle_enter_common();

	rcu_idle_enter_common(oldval);

	local_irq_restore(flags);

}
@@ -92,11 +95,13 @@ void rcu_idle_enter(void) 
void rcu_irq_exit(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_enter_common();

	rcu_idle_enter_common(oldval);

	local_irq_restore(flags);

}
@@ -104,14 +109,15 @@ void rcu_irq_exit(void) 
static void rcu_idle_exit_common(long long oldval)

{

	if (oldval) {

		RCU_TRACE(trace_rcu_dyntick("++=", rcu_dynticks_nesting));

		RCU_TRACE(trace_rcu_dyntick("++=",

					    oldval, rcu_dynticks_nesting));

		return;

	}

	RCU_TRACE(trace_rcu_dyntick("End", oldval));

	RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));

	if (!idle_cpu(smp_processor_id())) {

		WARN_ON_ONCE(1);	/* must be idle task! */

		RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",

			  oldval));

			  oldval, rcu_dynticks_nesting));

		ftrace_dump(DUMP_ALL);

	}

}
@@ -127,7 +133,7 @@ void rcu_idle_exit(void) 
	local_irq_save(flags);

	oldval = rcu_dynticks_nesting;

	WARN_ON_ONCE(oldval != 0);

	rcu_dynticks_nesting = LLONG_MAX / 2;

	rcu_dynticks_nesting = DYNTICK_TASK_NESTING;

	rcu_idle_exit_common(oldval);

	local_irq_restore(flags);

}

kernel/rcutree.c

+20 −15
Original line number Diff line number Diff line
@@ -196,7 +196,7 @@ void rcu_note_context_switch(int cpu) 
EXPORT_SYMBOL_GPL(rcu_note_context_switch);



DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {

	.dynticks_nesting = LLONG_MAX / 2,

	.dynticks_nesting = DYNTICK_TASK_NESTING,

	.dynticks = ATOMIC_INIT(1),

};
@@ -348,17 +348,17 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp) 
 * we really have entered idle, and must do the appropriate accounting.

 * The caller must have disabled interrupts.

 */

static void rcu_idle_enter_common(struct rcu_dynticks *rdtp)

static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)

{

	if (rdtp->dynticks_nesting) {

		trace_rcu_dyntick("--=", rdtp->dynticks_nesting);

		trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);

		return;

	}

	trace_rcu_dyntick("Start", rdtp->dynticks_nesting);

	trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);

	if (!idle_cpu(smp_processor_id())) {

		WARN_ON_ONCE(1);	/* must be idle task! */

		trace_rcu_dyntick("Error on entry: not idle task",

				   rdtp->dynticks_nesting);

				   oldval, rdtp->dynticks_nesting);

		ftrace_dump(DUMP_ALL);

	}

	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
@@ -383,12 +383,14 @@ static void rcu_idle_enter_common(struct rcu_dynticks *rdtp) 
void rcu_idle_enter(void)

{

	unsigned long flags;

	long long oldval;

	struct rcu_dynticks *rdtp;



	local_irq_save(flags);

	rdtp = &__get_cpu_var(rcu_dynticks);

	oldval = rdtp->dynticks_nesting;

	rdtp->dynticks_nesting = 0;

	rcu_idle_enter_common(rdtp);

	rcu_idle_enter_common(rdtp, oldval);

	local_irq_restore(flags);

}
@@ -411,13 +413,15 @@ void rcu_idle_enter(void) 
void rcu_irq_exit(void)

{

	unsigned long flags;

	long long oldval;

	struct rcu_dynticks *rdtp;



	local_irq_save(flags);

	rdtp = &__get_cpu_var(rcu_dynticks);

	oldval = rdtp->dynticks_nesting;

	rdtp->dynticks_nesting--;

	WARN_ON_ONCE(rdtp->dynticks_nesting < 0);

	rcu_idle_enter_common(rdtp);

	rcu_idle_enter_common(rdtp, oldval);

	local_irq_restore(flags);

}
@@ -431,7 +435,7 @@ void rcu_irq_exit(void) 
static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)

{

	if (oldval) {

		trace_rcu_dyntick("++=", rdtp->dynticks_nesting);

		trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting);

		return;

	}

	smp_mb__before_atomic_inc();  /* Force ordering w/previous sojourn. */
@@ -439,10 +443,11 @@ static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) 
	/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */

	smp_mb__after_atomic_inc();  /* See above. */

	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));

	trace_rcu_dyntick("End", oldval);

	trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);

	if (!idle_cpu(smp_processor_id())) {

		WARN_ON_ONCE(1);	/* must be idle task! */

		trace_rcu_dyntick("Error on exit: not idle task", oldval);

		trace_rcu_dyntick("Error on exit: not idle task",

				  oldval, rdtp->dynticks_nesting);

		ftrace_dump(DUMP_ALL);

	}

}
@@ -453,8 +458,8 @@ static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) 
 * Exit idle mode, in other words, -enter- the mode in which RCU

 * read-side critical sections can occur.

 *

 * We crowbar the ->dynticks_nesting field to LLONG_MAX/2 to allow for

 * the possibility of usermode upcalls messing up our count

 * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NESTING to

 * allow for the possibility of usermode upcalls messing up our count

 * of interrupt nesting level during the busy period that is just

 * now starting.

 */
@@ -468,7 +473,7 @@ void rcu_idle_exit(void) 
	rdtp = &__get_cpu_var(rcu_dynticks);

	oldval = rdtp->dynticks_nesting;

	WARN_ON_ONCE(oldval != 0);

	rdtp->dynticks_nesting = LLONG_MAX / 2;

	rdtp->dynticks_nesting = DYNTICK_TASK_NESTING;

	rcu_idle_exit_common(rdtp, oldval);

	local_irq_restore(flags);

}
@@ -2012,7 +2017,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) 
		rdp->nxttail[i] = &rdp->nxtlist;

	rdp->qlen = 0;

	rdp->dynticks = &per_cpu(rcu_dynticks, cpu);

	WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);

	WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_NESTING);

	WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);

	rdp->cpu = cpu;

	rdp->rsp = rsp;
@@ -2040,7 +2045,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) 
	rdp->qlen_last_fqs_check = 0;

	rdp->n_force_qs_snap = rsp->n_force_qs;

	rdp->blimit = blimit;

	WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != LLONG_MAX / 2);

	WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_NESTING);

	WARN_ON_ONCE((atomic_read(&rdp->dynticks->dynticks) & 0x1) != 1);

	raw_spin_unlock(&rnp->lock);		/* irqs remain disabled. */

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