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perf/core: Always set cpuctx cgrp when enable cgroup event

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When enable a cgroup event, cpuctx->cgrp setting is conditional
on the current task cgrp matching the event's cgroup, so have to
do it for every new event. It brings complexity but no advantage.

To keep it simple, this patch would always set cpuctx->cgrp
when enable the first cgroup event, and reset to NULL when disable
the last cgroup event.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220329154523.86438-5-zhouchengming@bytedance.com
This commit is contained in:
Chengming Zhou 2022-03-29 23:45:23 +08:00 • committed by Peter Zijlstra
parent 96492a6c55
commit e19cd0b6fa
1 changed files with 2 additions and 16 deletions
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18
kernel/events/core.c
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@ -967,22 +967,10 @@ perf_cgroup_event_enable(struct perf_event *event, struct perf_event_context *ct
*/
cpuctx = container_of(ctx, struct perf_cpu_context, ctx);
/*
* Since setting cpuctx->cgrp is conditional on the current @cgrp
* matching the event's cgroup, we must do this for every new event,
* because if the first would mismatch, the second would not try again
* and we would leave cpuctx->cgrp unset.
*/
if (ctx->is_active && !cpuctx->cgrp) {
struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);
if (cgroup_is_descendant(cgrp->css.cgroup, event->cgrp->css.cgroup))
cpuctx->cgrp = cgrp;
}
if (ctx->nr_cgroups++)
return;
cpuctx->cgrp = perf_cgroup_from_task(current, ctx);
list_add(&cpuctx->cgrp_cpuctx_entry,
per_cpu_ptr(&cgrp_cpuctx_list, event->cpu));
}
@ -1004,9 +992,7 @@ perf_cgroup_event_disable(struct perf_event *event, struct perf_event_context *c
if (--ctx->nr_cgroups)
return;
if (ctx->is_active && cpuctx->cgrp)
cpuctx->cgrp = NULL;
cpuctx->cgrp = NULL;
list_del(&cpuctx->cgrp_cpuctx_entry);
}