From nobody Mon Feb 9 04:28:49 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 81A37C77B75 for ; Tue, 16 May 2023 03:42:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229642AbjEPDmZ (ORCPT ); Mon, 15 May 2023 23:42:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47526 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229529AbjEPDmX (ORCPT ); Mon, 15 May 2023 23:42:23 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E7A755A4 for ; Mon, 15 May 2023 20:42:22 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id 41be03b00d2f7-5340957c397so1202533a12.2 for ; Mon, 15 May 2023 20:42:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1684208541; x=1686800541; h=content-transfer-encoding:cc:to:from:subject:message-id :mime-version:date:from:to:cc:subject:date:message-id:reply-to; bh=QfakjCCfwFt+mIB9AT5nkofxGKZ/CvaVo69e1r5gk1A=; b=EhBoZybb/5zbx0jCyhuVRYEzB7CdoPFz543LQUtWqQM4QQ9lH/RWwABYlF/w/TQE+s MFWKqc8gbVDGpEgNZFNL53EaqKEk/FCXjQlVgQhPFj9GmcGt0pPW2gbem3ExJPbstLQI yRh8OS60LDRcMiNPhHJr0v6VnHy4JHCu4v45DeBlPT3fFTCEE3YaI09rfNi7mxuGF4EY mwMSWA0z5Fm8VgAX7MIyiOX1xcvYfBJcPNwTqHEGj1yZUzwjsQNtSQodV6g2bY7Un1h/ KA6Ihza/OO8L4T+UWSiXz52SMp6Y/cKWBpU8JQKOmoarsnm0mWcX0Lz9o6+djmDisua6 HeWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1684208541; x=1686800541; h=content-transfer-encoding:cc:to:from:subject:message-id :mime-version:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=QfakjCCfwFt+mIB9AT5nkofxGKZ/CvaVo69e1r5gk1A=; b=BGWXJ7ayDJyf6tDLfeYPDPz3lqS1BJlnZL31se7YgSv11hcF6gmL+FqafYT5nFRBaW ekvqEfWKjAHFHCuMrej31dsKhyft+JJprqDM5LfWFeyVBKXgKfZ/gLEoHap6vO6iJ2Ez Ks1V5vHhMQL/tMG4Ou8et8mZF4BpV0bNkykTT5vety6p7ecZReqXwg8IvWYM1JprcxqX Ej6Nh/RPQVs/YFtLZdrKt4SZ6a+PVvzukcEc90jnbdLe7LCLVSx2HA8NrBRdVUdlMgY3 1H0+CBuB11F+4fLBSG3ai0f1N0Ls/b6uh9yk/d9VQp1g1/OUhQ+T9CuwSXA9V7n6jg8v XvRw== X-Gm-Message-State: AC+VfDzWUOrVu3ELvdrZ0iiGgHLp6fqmF4gp8pe3OP7N0oDs73wtlAml ujpyRgetRdeNqCfMGpdo7XX9oA5byvUCRrbsG3MHj/tXpxI1m/ga0zZ/5Q+1HAkQGZodxDGPTMc hlkAjhvl8tRsvfZM13UfsHHd2mOGo8hjUuQeHIAzQKWjMi+fmQrKyYwDom9ZANn8NtmTydBE= X-Google-Smtp-Source: ACHHUZ4sqKNlx2tjDfNXgCMyzJzsAbqTNhgzIsDUZkSJ4N44sAU8G6n9vZXNnCtVtQA1z5AuAm/bFtuVfZkv X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a63:8ac1:0:b0:52c:8878:65dc with SMTP id y184-20020a638ac1000000b0052c887865dcmr10381889pgd.1.1684208541169; Mon, 15 May 2023 20:42:21 -0700 (PDT) Date: Tue, 16 May 2023 03:41:48 +0000 Mime-Version: 1.0 X-Mailer: git-send-email 2.40.1.606.ga4b1b128d6-goog Message-ID: <20230516034207.3847143-1-jstultz@google.com> Subject: [PATCH v2] sched/wait: Fix a kthread_park race with wait_woken() From: John Stultz To: LKML Cc: "=?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?=" , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , android-kernel-team , John Stultz Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Arve Hj=C3=B8nnev=C3=A5g kthread_park and wait_woken have a similar race that kthread_stop and wait_woken used to have before it was fixed in commit cb6538e740d7 ("sched/wait: Fix a kthread race with wait_woken()"). Extend that fix to also cover kthread_park. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Valentin Schneider Cc: android-kernel-team Signed-off-by: Arve Hj=C3=B8nnev=C3=A5g [jstultz: Made changes suggested by Peter to optimize memory loads] Signed-off-by: John Stultz --- v2: * Commit message tweaks, suggested by Peter * Move logic to kthread.c & optimize to avoid duplicate memory loads, also suggested by Peter --- include/linux/kthread.h | 1 + kernel/kthread.c | 10 ++++++++++ kernel/sched/wait.c | 7 +------ 3 files changed, 12 insertions(+), 6 deletions(-) diff --git a/include/linux/kthread.h b/include/linux/kthread.h index 30e5bec81d2b..f1f95a71a4bc 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -89,6 +89,7 @@ int kthread_stop(struct task_struct *k); bool kthread_should_stop(void); bool kthread_should_park(void); bool __kthread_should_park(struct task_struct *k); +bool kthread_should_stop_or_park(void); bool kthread_freezable_should_stop(bool *was_frozen); void *kthread_func(struct task_struct *k); void *kthread_data(struct task_struct *k); diff --git a/kernel/kthread.c b/kernel/kthread.c index 490792b1066e..07a057086d26 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -182,6 +182,16 @@ bool kthread_should_park(void) } EXPORT_SYMBOL_GPL(kthread_should_park); =20 +bool kthread_should_stop_or_park(void) +{ + struct kthread *kthread =3D __to_kthread(current); + + if (!kthread) + return false; + + return kthread->flags & (BIT(KTHREAD_SHOULD_STOP) | BIT(KTHREAD_SHOULD_PA= RK)); +} + /** * kthread_freezable_should_stop - should this freezable kthread return no= w? * @was_frozen: optional out parameter, indicates whether %current was fro= zen diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index 133b74730738..48c53e4739ea 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -425,11 +425,6 @@ int autoremove_wake_function(struct wait_queue_entry *= wq_entry, unsigned mode, i } EXPORT_SYMBOL(autoremove_wake_function); =20 -static inline bool is_kthread_should_stop(void) -{ - return (current->flags & PF_KTHREAD) && kthread_should_stop(); -} - /* * DEFINE_WAIT_FUNC(wait, woken_wake_func); * @@ -459,7 +454,7 @@ long wait_woken(struct wait_queue_entry *wq_entry, unsi= gned mode, long timeout) * or woken_wake_function() sees our store to current->state. */ set_current_state(mode); /* A */ - if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop()) + if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !kthread_should_stop_or_park()) timeout =3D schedule_timeout(timeout); __set_current_state(TASK_RUNNING); =20 --=20 2.40.1.606.ga4b1b128d6-goog