On Thu, Dec 15, 2022 at 11:57:55AM +0800, Zqiang wrote:
> Currently, if the system is in the RCU_SCHEDULER_INACTIVE state, invoke
> synchronize_rcu_*() will implies a grace period and return directly,
> so there is no sleep action due to waiting for a grace period to end,
> but this might_sleep() check is the opposite. therefore, this commit
> puts might_sleep() check in the correct palce.
>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
>
>Queued for testing and review, thank you!
>
>I was under the impression that might_sleep() did some lockdep-based
>checking, but I am unable to find it. If there really is such checking,
>that would be a potential argument for leaving this code as it is.
>
__might_sleep
__might_resched(file, line, 0)
rcu_sleep_check()
Does it refer to this rcu_sleep_check() ?
If so, when in the RCU_SCHEDULER_INACTIVE state, the debug_lockdep_rcu_enabled() is always
return false, so the RCU_LOCKDEP_WARN() also does not produce an actual warning.
Thanks
Zqiang
>But in the meantime, full speed ahead! ;-)
>
> Thanx, Paul
>
> ---
> kernel/rcu/tree.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index ee8a6a711719..65f3dd2fd3ae 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3379,9 +3379,10 @@ void __init kfree_rcu_scheduler_running(void)
> */
> static int rcu_blocking_is_gp(void)
> {
> - if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
> + if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE) {
> + might_sleep();
> return false;
> - might_sleep(); /* Check for RCU read-side critical section. */
> + }
> return true;
> }
>
> --
> 2.25.1
>
