From nobody Wed Dec 17 05:49:21 2025 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 4A0C1C4167B for ; Wed, 29 Nov 2023 15:08:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234521AbjK2PIl (ORCPT ); Wed, 29 Nov 2023 10:08:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234844AbjK2Ozk (ORCPT ); Wed, 29 Nov 2023 09:55:40 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2045310DF; Wed, 29 Nov 2023 06:55:45 -0800 (PST) Date: Wed, 29 Nov 2023 14:55:43 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1701269743; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=u7fdg9HsOCuKA61WgZU0Q3a150uw7ZsSmWZm77p0STY=; b=3VS2nUxhbvX0YkzobvkabVg1G3ZXYUUY0jsOHrr1xGUq925nsPWUfxr+Pe+Uj1OA9ECpMP YK24kCIQjXaT3FOwFPZAcWo4rIrJKB+ScNMprL93VsHStttXFHe7YUtUAFvMt2VkGDXg0S hzvJitaCLYKZmqlm08WTE4ExFf0jnPbapHlxhBoslbH3bfn/7leN4hLCLxkkmovPyUVUGa XE1CFmGKsNk1np+UC4Zt7ktOv2uUf4Hm/pfMQGg/ZrrL+WC10uF/8N58NRSMLqsbH8WJzd VGI7eRuYv+6/HLQE4wnkFSbo/UQ9SyXJtZANpLFUpfof+q3T2jQEYf1NF4iNRA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1701269743; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=u7fdg9HsOCuKA61WgZU0Q3a150uw7ZsSmWZm77p0STY=; b=Fp0sg0f3pICor0IYtjwps1teD4BvPlL6tKD7Z/lZmK7hU5NZggyIUwRj6UC3jpDt4XhAZY TnGK6OytYQMq14DA== From: "tip-bot2 for Elliot Berman" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] freezer,sched: Do not restore saved_state of a thawed task Cc: Elliot Berman , "Peter Zijlstra (Intel)" , Abhijeet Dharmapurikar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20231120-freezer-state-multiple-thaws-v1-1-f2e1dd7ce5a2@quicinc.com> References: <20231120-freezer-state-multiple-thaws-v1-1-f2e1dd7ce5a2@quicinc.com> MIME-Version: 1.0 Message-ID: <170126974302.398.5668977195119638525.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/urgent branch of tip: Commit-ID: 23ab79e8e469e2605beec2e3ccb40d19c68dd2e0 Gitweb: https://git.kernel.org/tip/23ab79e8e469e2605beec2e3ccb40d19c= 68dd2e0 Author: Elliot Berman AuthorDate: Mon, 20 Nov 2023 09:36:31 -08:00 Committer: Peter Zijlstra CommitterDate: Wed, 29 Nov 2023 15:43:48 +01:00 freezer,sched: Do not restore saved_state of a thawed task It is possible for a task to be thawed multiple times when mixing the *legacy* cgroup freezer and system-wide freezer. To do this, freeze the cgroup, do system-wide freeze/thaw, then thaw the cgroup. When this happens, then a stale saved_state can be written to the task's state and cause task to hang indefinitely. Fix this by only trying to thaw tasks that are actually frozen. This change also has the marginal benefit avoiding unnecessary wake_up_state(p, TASK_FROZEN) if we know the task is already thawed. There is not possibility of time-of-compare/time-of-use race when we skip the wake_up_state because entering/exiting TASK_FROZEN is guarded by freezer_lock. Fixes: 8f0eed4a78a8 ("freezer,sched: Use saved_state to reduce some spuriou= s wakeups") Signed-off-by: Elliot Berman Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Abhijeet Dharmapurikar Link: https://lore.kernel.org/r/20231120-freezer-state-multiple-thaws-v1-1-= f2e1dd7ce5a2@quicinc.com --- kernel/freezer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/freezer.c b/kernel/freezer.c index c450fa8..759006a 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -201,7 +201,7 @@ void __thaw_task(struct task_struct *p) if (WARN_ON_ONCE(freezing(p))) goto unlock; =20 - if (task_call_func(p, __restore_freezer_state, NULL)) + if (!frozen(p) || task_call_func(p, __restore_freezer_state, NULL)) goto unlock; =20 wake_up_state(p, TASK_FROZEN);