From: Vincent Donnefort vincent.donnefort@arm.com
stable inclusion form stable-v5.10.82 commit 68fcb52b610c1853cadf3d135415555a128355f9 bugzilla: 185877 https://gitee.com/openeuler/kernel/issues/I4QU6V
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit 42dc938a590c96eeb429e1830123fef2366d9c80 ]
Nothing protects the access to the per_cpu variable sd_llc_id. When testing the same CPU (i.e. this_cpu == that_cpu), a race condition exists with update_top_cache_domain(). One scenario being:
CPU1 CPU2 ==================================================================
per_cpu(sd_llc_id, CPUX) => 0 partition_sched_domains_locked() detach_destroy_domains() cpus_share_cache(CPUX, CPUX) update_top_cache_domain(CPUX) per_cpu(sd_llc_id, CPUX) => 0 per_cpu(sd_llc_id, CPUX) = CPUX per_cpu(sd_llc_id, CPUX) => CPUX return false
ttwu_queue_cond() wouldn't catch smp_processor_id() == cpu and the result is a warning triggered from ttwu_queue_wakelist().
Avoid a such race in cpus_share_cache() by always returning true when this_cpu == that_cpu.
Fixes: 518cd6234178 ("sched: Only queue remote wakeups when crossing cache boundaries") Reported-by: Jing-Ting Wu jing-ting.wu@mediatek.com Signed-off-by: Vincent Donnefort vincent.donnefort@arm.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Valentin Schneider valentin.schneider@arm.com Reviewed-by: Vincent Guittot vincent.guittot@linaro.org Link: https://lore.kernel.org/r/20211104175120.857087-1-vincent.donnefort@arm.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Chen Jun chenjun102@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- kernel/sched/core.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 93961898567b..02de67c01aa9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2647,6 +2647,9 @@ void wake_up_if_idle(int cpu)
bool cpus_share_cache(int this_cpu, int that_cpu) { + if (this_cpu == that_cpu) + return true; + return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); }