From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 92AF52192EC; Mon, 23 Jun 2025 22:25:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750717517; cv=none; b=ezGM2X0CuMQWtHKjHZ7BrqwboGUI4mT3jSW1PxY5LwcPvSU8V607u4h4/dZIDHTxsfHbUAdZa5utnQDSpxDzZb4tA8gnOTT+C8NdaYbcRDi3ZwDo8ge4uo0BCROpiqxROeeWbjSLBIdOfJgW2/+ZQIJRABlTOP9hMxd1LQjTBGI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750717517; c=relaxed/simple; bh=WxrMm/OvvnuNb7MwZM/afEptVpi1Y42iunKi3K/QmzA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=U1vW/7zqygQOvY7QSuafshNyqRd8o5Tip+no8nv/vcj59CDst1n1RIencTZs26NaRxmzNYxQSJ4kKNiEAWEG1pHyQbypr3mC3ccfXC/62qk9q2F2rbXWIPZqCR+Yto6vUCrSHXoMG6Zp9Lab/M9/YG3OSN0+cRE40uzk6vbfhr0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=MPQVciGv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="MPQVciGv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1AFBC4CEEA; Mon, 23 Jun 2025 22:25:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750717516; bh=WxrMm/OvvnuNb7MwZM/afEptVpi1Y42iunKi3K/QmzA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MPQVciGv186aNLUb9lneWxUklTFbTCbX76SrDgsrllZU4vT0hui+rpywvlrQ0K/4c A3UiDhHVW1D9GlmMiqi/9q5a1BhPjY7rK6rH0n4vRg4z9HJ+d2fxYDoHKFKc1MunoM X+wR/GbnC/t5TxtamRBR00hBfhljrEXsXWhA1Ecs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Luo Gengkun , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 6.12 405/414] perf/core: Fix WARN in perf_cgroup_switch() Date: Mon, 23 Jun 2025 15:09:02 +0200 Message-ID: <20250623130652.063159565@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130642.015559452@linuxfoundation.org> References: <20250623130642.015559452@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Luo Gengkun [ Upstream commit 3172fb986666dfb71bf483b6d3539e1e587fa197 ] 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); [peterz: use guard instead of goto unlock] Fixes: db4a835601b7 ("perf/core: Set cgroup in CPU contexts for new cgroup events") Signed-off-by: Luo Gengkun Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20250604033924.3914647-3-luogengkun@huaweicloud.com Signed-off-by: Sasha Levin --- kernel/events/core.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 3389a5a2724df..7210104b3345c 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -206,6 +206,19 @@ static void perf_ctx_unlock(struct perf_cpu_context *cpuctx, __perf_ctx_unlock(&cpuctx->ctx); } +typedef struct { + struct perf_cpu_context *cpuctx; + struct perf_event_context *ctx; +} class_perf_ctx_lock_t; + +static inline void class_perf_ctx_lock_destructor(class_perf_ctx_lock_t *_T) +{ perf_ctx_unlock(_T->cpuctx, _T->ctx); } + +static inline class_perf_ctx_lock_t +class_perf_ctx_lock_constructor(struct perf_cpu_context *cpuctx, + struct perf_event_context *ctx) +{ perf_ctx_lock(cpuctx, ctx); return (class_perf_ctx_lock_t){ cpuctx, ctx }; } + #define TASK_TOMBSTONE ((void *)-1L) static bool is_kernel_event(struct perf_event *event) @@ -898,7 +911,13 @@ static void perf_cgroup_switch(struct task_struct *task) if (READ_ONCE(cpuctx->cgrp) == cgrp) return; - perf_ctx_lock(cpuctx, cpuctx->task_ctx); + guard(perf_ctx_lock)(cpuctx, cpuctx->task_ctx); + /* + * Re-check, could've raced vs perf_remove_from_context(). + */ + if (READ_ONCE(cpuctx->cgrp) == NULL) + return; + perf_ctx_disable(&cpuctx->ctx, true); ctx_sched_out(&cpuctx->ctx, NULL, EVENT_ALL|EVENT_CGROUP); @@ -916,7 +935,6 @@ 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); - perf_ctx_unlock(cpuctx, cpuctx->task_ctx); } static int perf_cgroup_ensure_storage(struct perf_event *event, -- 2.39.5