Commit 07c59729 authored Jan 22, 2020 by Song Liu Committed by Ingo Molnar Jan 28, 2020

perf/cgroups: Install cgroup events to correct cpuctx



cgroup events are always installed in the cpuctx. However, when it is not
installed via IPI, list_update_cgroup_event() adds it to cpuctx of current
CPU, which triggers list corruption:

  [] list_add double add: new=ffff888ff7cf0db0, prev=ffff888ff7ce82f0, next=ffff888ff7cf0db0.

To reproduce this, we can simply run:

  # perf stat -e cs -a &
  # perf stat -e cs -G anycgroup

Fix this by installing it to cpuctx that contains event->ctx, and the
proper cgrp_cpuctx_list.

Fixes: db0503e4 ("perf/core: Optimize perf_install_in_event()")
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200122195027.2112449-1-songliubraving@fb.com

parent 00346155

kernel/events/core.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -951,9 +951,9 @@ list_update_cgroup_event(struct perf_event *event,

		/*
		* Because cgroup events are always per-cpu events,
		* this will always be called from the right CPU.
		* @ctx == &cpuctx->ctx.
		*/
		cpuctx = __get_cpu_context(ctx);
		cpuctx = container_of(ctx, struct perf_cpu_context, ctx);

		/*
		* Since setting cpuctx->cgrp is conditional on the current @cgrp
		@@ -979,7 +979,8 @@ list_update_cgroup_event(struct perf_event *event,

		cpuctx_entry = &cpuctx->cgrp_cpuctx_entry;
		if (add)
		list_add(cpuctx_entry, this_cpu_ptr(&cgrp_cpuctx_list));
		list_add(cpuctx_entry,
		per_cpu_ptr(&cgrp_cpuctx_list, event->cpu));
		else
		list_del(cpuctx_entry);
		}

Admin message