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Commit e68bbb26 authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Simplify rcu_eqs_{enter,exit}() non-idle task debug code 



The code that checks for non-idle non-nohz_idle-usermode tasks invoking
rcu_eqs_enter() and rcu_eqs_exit() prints a considerable quantity of
helpful information.  However, these checks fire rarely, so the extra
complexity is no longer worth it.  This commit therefore replaces this
debug code with simple WARN_ON_ONCE() statements.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 9dd238e2

include/trace/events/rcu.h

+5 −7
Original line number Diff line number Diff line
@@ -424,15 +424,13 @@ TRACE_EVENT(rcu_fqs, 
 * as argument: "Start" for entering dyntick-idle mode, "Startirq" for

 * entering it from irq/NMI, "End" for leaving it, "Endirq" for leaving it

 * to irq/NMI, "--=" for events moving towards idle, and "++=" for events

 * moving away from idle.  "Error on entry: not idle task" and "Error

 * on exit: not idle task" indicate that a non-idle task is erroneously

 * toying with the idle loop.

 * moving away from idle.

 *

 * These events also take a pair of numbers, which indicate the nesting

 * depth before and after the event of interest.  Note that task-related

 * and interrupt-related events use two separate counters, and that the

 * "++=" and "--=" events for irq/NMI will change the counter by two,

 * otherwise by one.

 * depth before and after the event of interest, and a third number that is

 * the ->dynticks counter.  Note that task-related and interrupt-related

 * events use two separate counters, and that the "++=" and "--=" events

 * for irq/NMI will change the counter by two, otherwise by one.

 */

TRACE_EVENT(rcu_dyntick,

kernel/rcu/tree.c

+2 −22
Original line number Diff line number Diff line
@@ -773,17 +773,7 @@ static void rcu_eqs_enter(bool user) 


	lockdep_assert_irqs_disabled();

	trace_rcu_dyntick(TPS("Start"), rdtp->dynticks_nesting, 0, rdtp->dynticks);

	if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&

	    !user && !is_idle_task(current)) {

		struct task_struct *idle __maybe_unused =

			idle_task(smp_processor_id());



		trace_rcu_dyntick(TPS("Error on entry: not idle task"), rdtp->dynticks_nesting, 0, rdtp->dynticks);

		rcu_ftrace_dump(DUMP_ORIG);

		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! */

	}

	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));

	for_each_rcu_flavor(rsp) {

		rdp = this_cpu_ptr(rsp->rda);

		do_nocb_deferred_wakeup(rdp);
@@ -941,17 +931,7 @@ static void rcu_eqs_exit(bool user) 
	rcu_dynticks_eqs_exit();

	rcu_cleanup_after_idle();

	trace_rcu_dyntick(TPS("End"), rdtp->dynticks_nesting, 1, rdtp->dynticks);

	if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&

	    !user && !is_idle_task(current)) {

		struct task_struct *idle __maybe_unused =

			idle_task(smp_processor_id());



		trace_rcu_dyntick(TPS("Error on exit: not idle task"), rdtp->dynticks_nesting, 1, rdtp->dynticks);

		rcu_ftrace_dump(DUMP_ORIG);

		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! */

	}

	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));

	WRITE_ONCE(rdtp->dynticks_nesting, 1);

	WRITE_ONCE(rdtp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);

}