On Tue, Mar 28, 2023 at 06:16:33AM +0000, Yosry Ahmed wrote:
> rstat flushing is too expensive to perform in irq context.
> The previous patch removed the only context that may invoke an rstat
> flush from irq context, add a WARN_ON_ONCE() to detect future
> violations, or those that we are not aware of.
>
> Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> ---
> kernel/cgroup/rstat.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
> index d3252b0416b6..c2571939139f 100644
> --- a/kernel/cgroup/rstat.c
> +++ b/kernel/cgroup/rstat.c
> @@ -176,6 +176,8 @@ static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
> {
> int cpu;
>
> + /* rstat flushing is too expensive for irq context */
> + WARN_ON_ONCE(!in_task());
> lockdep_assert_held(&cgroup_rstat_lock);
This seems a bit arbitrary. Why is an irq caller forbidden, but an
irq-disabled, non-preemptible section caller is allowed? The latency
impact on the system would be the same, right?
