From nobody Thu Apr 2 22:59:32 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70B13C6FA82 for ; Tue, 20 Sep 2022 01:45:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229805AbiITBpV (ORCPT ); Mon, 19 Sep 2022 21:45:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229612AbiITBpP (ORCPT ); Mon, 19 Sep 2022 21:45:15 -0400 Received: from zju.edu.cn (mail.zju.edu.cn [61.164.42.155]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 36C0540BFC; Mon, 19 Sep 2022 18:45:12 -0700 (PDT) Received: from ubuntu.localdomain (unknown [10.162.98.155]) by mail-app3 (Coremail) with SMTP id cC_KCgBnbQwPGyljNLDDBg--.19579S2; Tue, 20 Sep 2022 09:44:53 +0800 (CST) From: Duoming Zhou To: peterz@infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Cc: mingo@redhat.com, acme@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, tglx@linutronix.de, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, Duoming Zhou Subject: [PATCH V2] perf/x86/rapl: fix deadlock in rapl_pmu_event_stop Date: Tue, 20 Sep 2022 09:44:47 +0800 Message-Id: <20220920014447.71946-1-duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 X-CM-TRANSID: cC_KCgBnbQwPGyljNLDDBg--.19579S2 X-Coremail-Antispam: 1UD129KBjvJXoW7ZF47XryxCr4rWFW5WFyfWFg_yoW8AFWrpr WxAFy5tF1jv3Z2qayUK3WkXw4fua1kXanrJryfGw1rAan8Wan8J3W8WayFvF45JrZ7XasI yw10qrWrAFyDAa7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvm1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVWxJr0_GcWl84ACjcxK6I8E 87Iv67AKxVW0oVCq3wA2z4x0Y4vEx4A2jsIEc7CjxVAFwI0_GcCE3s1le2I262IYc4CY6c 8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_Jr0_ Jr4lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE7xkEbVWUJVW8JwACjcxG0xvY0x0EwI xGrwACjI8F5VA0II8E6IAqYI8I648v4I1lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IY c2Ij64vIr41l42xK82IY6x8ErcxFaVAv8VW8uw4UJr1UMxC20s026xCaFVCjc4AY6r1j6r 4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF 67AKxVWUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2I x0cI8IcVCY1x0267AKxVW8JVWxJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2 z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnU UI43ZEXa7VUbXdbUUUUUU== X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/1tbiAgkTAVZdtbikRgAHs6 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" There is a deadlock in rapl_pmu_event_stop(), the process is shown below: (thread 1) | (thread 2) rapl_pmu_event_stop() | rapl_hrtimer_handle() ... | if (!pmu->n_active) raw_spin_lock_irqsave() //(1) | ... ... | hrtimer_cancel() | raw_spin_lock_irqsave() //(2) (block forever) We hold pmu->lock in position (1) and use hrtimer_cancel() to wait rapl_hrtimer_handle() to stop, but rapl_hrtimer_handle() also need pmu->lock in position (2). As a result, the rapl_pmu_event_stop() will be blocked forever. This patch extracts hrtimer_cancel() from the protection of raw_spin_lock_irqsave(). As a result, the rapl_hrtimer_handle() could obtain the pmu->lock. Fixes: 65661f96d3b3 ("perf/x86: Add RAPL hrtimer support") Signed-off-by: Duoming Zhou --- Changes in v2: - Move hrtimer_cancel() to the end of rapl_pmu_event_stop() function. arch/x86/events/rapl.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/events/rapl.c b/arch/x86/events/rapl.c index 77e3a47af5a..7c110092c83 100644 --- a/arch/x86/events/rapl.c +++ b/arch/x86/events/rapl.c @@ -281,8 +281,6 @@ static void rapl_pmu_event_stop(struct perf_event *even= t, int mode) if (!(hwc->state & PERF_HES_STOPPED)) { WARN_ON_ONCE(pmu->n_active <=3D 0); pmu->n_active--; - if (pmu->n_active =3D=3D 0) - hrtimer_cancel(&pmu->hrtimer); =20 list_del(&event->active_entry); =20 @@ -300,6 +298,11 @@ static void rapl_pmu_event_stop(struct perf_event *eve= nt, int mode) hwc->state |=3D PERF_HES_UPTODATE; } =20 + if (!pmu->n_active) { + raw_spin_unlock_irqrestore(&pmu->lock, flags); + hrtimer_cancel(&pmu->hrtimer); + return; + } raw_spin_unlock_irqrestore(&pmu->lock, flags); } =20 --=20 2.17.1