Commit 2c00e119 authored by Ankur Arora's avatar Ankur Arora Committed by Boqun Feng
Browse files

sched: update __cond_resched comment about RCU quiescent states 



Update comment in __cond_resched() clarifying how urgently needed
quiescent state are provided.

Signed-off-by: default avatarAnkur Arora <ankur.a.arora@oracle.com>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
parent 4dca1af4

kernel/sched/core.c

+3 −1
Original line number Diff line number Diff line
@@ -7289,7 +7289,7 @@ int __sched __cond_resched(void) 
		return 1;

	}

	/*

	 * In preemptible kernels, ->rcu_read_lock_nesting tells the tick

	 * In PREEMPT_RCU kernels, ->rcu_read_lock_nesting tells the tick

	 * whether the current CPU is in an RCU read-side critical section,

	 * so the tick can report quiescent states even for CPUs looping

	 * in kernel context.  In contrast, in non-preemptible kernels,
@@ -7298,6 +7298,8 @@ int __sched __cond_resched(void) 
	 * RCU quiescent state.  Therefore, the following code causes

	 * cond_resched() to report a quiescent state, but only when RCU

	 * is in urgent need of one.

	 * A third case, preemptible, but non-PREEMPT_RCU provides for

	 * urgently needed quiescent states via rcu_flavor_sched_clock_irq().

	 */

#ifndef CONFIG_PREEMPT_RCU

	rcu_all_qs();