From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from dggsgout12.his.huawei.com (dggsgout12.his.huawei.com [45.249.212.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D3DBF231828; Wed, 4 Jun 2025 03:23:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749007440; cv=none; b=EotZwPUhR4BEdYk8BI7enw+WKvMXHrtPss3GSdB6TL3597qkso8I5JYJspziFllZ2YOaxZEbcMRLZBt7q7CCIpT7E6C6If0gaIe9MqdgyDFXz+AtHd/QrCSgx6aeJQ57r1boQpX/iUQNRtZkJ34Xz5r8zo0yvL1twBup0RPVa2Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749007440; c=relaxed/simple; bh=KKCtxcNKDurQedRm8dJ/mP8QxHRVX5UPgpzxDkDohe8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Y7K8UMwUDjZ4iJ7Lb0XCE4LZnRBYNZsonFSKqV9Ooz+DnK31XEK9/yQc4lagOY5yzgesTlOBk+WGcfQGPxynlO7AGyWMpEVvtMKXTZ7+HoRnx058+L7TBBu4Wn8iRNFn6uyQe3W+wq33ZhjfsqHMMhmKuryKc5zlFcYOeUSir7w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.93.142]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4bBtGJ4Hq3zKHND7; Wed, 4 Jun 2025 11:23:52 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.112]) by mail.maildlp.com (Postfix) with ESMTP id F16FF1A118D; Wed, 4 Jun 2025 11:23:50 +0800 (CST) Received: from huaweicloud.com (unknown [10.67.174.193]) by APP1 (Coremail) with SMTP id cCh0CgC3GntEvD9ondLUOA--.11688S6; Wed, 04 Jun 2025 11:23:50 +0800 (CST) From: Luo Gengkun To: peterz@infradead.org Cc: mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, davidcc@google.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, luogengkun@huaweicloud.com Subject: [PATCH v2 2/2] perf/core: Fix WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0) in perf_cgroup_switch Date: Wed, 4 Jun 2025 03:39:24 +0000 Message-Id: <20250604033924.3914647-3-luogengkun@huaweicloud.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250604033924.3914647-1-luogengkun@huaweicloud.com> References: <20250604033924.3914647-1-luogengkun@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:cCh0CgC3GntEvD9ondLUOA--.11688S6 X-Coremail-Antispam: 1UD129KBjvJXoWxAF4DWr17XF1kuF1rZF1kXwb_yoW5GF47pa n7CrW29ws5XF90qay5t34vq3W0qa1Fqa95Wr1jkw4ayrW5Xr1fXF4xCw43JF15AFn7JFy3 trZ0vr15C34UKaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUQv14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_Jryl82xGYIkIc2 x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kIc2 xKxwCY1x0262kKe7AKxVWUtVW8ZwCF04k20xvY0x0EwIxGrwCF54CYxVCY1x0262kKe7AK xVWUtVW8ZwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r18MI8I3I 0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41lIxAI cVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr1lIxAIcV CF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r1j6r4UMIIF0xvEx4A2jsIE c7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUQXo7UUUUU= X-CM-SenderInfo: 5oxrwvpqjn3046kxt4xhlfz01xgou0bp/ There may be concurrency between perf_cgroup_switch and perf_cgroup_event_disable. Consider the following scenario: after a new perf cgroup event is created on CPU0, the new event may not trigger a reprogramming, causing ctx->is_active to be 0. In this case, when CPU1 disables this perf event, it executes __perf_remove_from_context-> list _del_event->perf_cgroup_event_disable on CPU1, which causes a race with perf_cgroup_switch running on CPU0. The following describes the details of this concurrency scenario: CPU0 CPU1 perf_cgroup_switch: ... # cpuctx->cgrp is not NULL here if (READ_ONCE(cpuctx->cgrp) == NULL) return; perf_remove_from_context: ... raw_spin_lock_irq(&ctx->lock); ... # ctx->is_active == 0 because reprogramm is not # tigger, so CPU1 can do __perf_remove_from_context # for CPU0 __perf_remove_from_context: perf_cgroup_event_disable: ... if (--ctx->nr_cgroups) ... # this warning will happened because CPU1 changed # ctx.nr_cgroups to 0. WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0); To fix this problem, expand the lock-holding critical section in perf_cgroup_switch. Fixes: db4a835601b7 ("perf/core: Set cgroup in CPU contexts for new cgroup events") Signed-off-by: Luo Gengkun --- kernel/events/core.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 280d42b40b34..1e442897ebde 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -931,20 +931,20 @@ static void perf_cgroup_switch(struct task_struct *task) struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context); struct perf_cgroup *cgrp; + cgrp = perf_cgroup_from_task(task, NULL); + perf_ctx_lock(cpuctx, cpuctx->task_ctx); /* * cpuctx->cgrp is set when the first cgroup event enabled, * and is cleared when the last cgroup event disabled. */ if (READ_ONCE(cpuctx->cgrp) == NULL) - return; + goto unlock; WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0); - cgrp = perf_cgroup_from_task(task, NULL); if (READ_ONCE(cpuctx->cgrp) == cgrp) - return; + goto unlock; - perf_ctx_lock(cpuctx, cpuctx->task_ctx); perf_ctx_disable(&cpuctx->ctx, true); ctx_sched_out(&cpuctx->ctx, NULL, EVENT_ALL|EVENT_CGROUP); @@ -962,6 +962,7 @@ static void perf_cgroup_switch(struct task_struct *task) ctx_sched_in(&cpuctx->ctx, NULL, EVENT_ALL|EVENT_CGROUP); perf_ctx_enable(&cpuctx->ctx, true); +unlock: perf_ctx_unlock(cpuctx, cpuctx->task_ctx); } -- 2.34.1