[3/9] sched: update __cond_resched comment about RCU quiescent states

Commit Message

Paul E. McKenney Jan. 16, 2025, 8:13 p.m. UTC

From: Ankur Arora <[e-mail]>

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

Signed-off-by: Ankur Arora <[e-mail]>
Reviewed-by: Frederic Weisbecker <[e-mail]>
Signed-off-by: Paul E. McKenney <[e-mail]>
---
 kernel/sched/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 95e40895a5190..b0f7ffcc46a66 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7281,7 +7281,7 @@  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,
@@ -7290,6 +7290,8 @@  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();