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 1BFFA8248B for ; Tue, 16 Sep 2025 04:07:57 +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=1757995677; cv=none; b=qg+yWpxNYZ9PeZplKb9esNfu+lKTGNhaoIfiwvedV56tg75Qy95v/l6ERGEZvf+h+Qy32bVfYgyQZlwpNeOcTvTUv6xihvCcK/1Gv6Zk95ejzw0I1Nfr41pijZ+J7sSdZO7mxPlBkzkC9wmSCOnBrNy6JWOVJDbl1wPsMLuJjMA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757995677; c=relaxed/simple; bh=RKJUVCWvFwzjN/Q37Y733wtl79nGCMwDcafr97JrFio=; h=Date:To:From:Subject:Message-Id; b=JXEUVbvUxPq9mXfXpeKooYjVAP4Roo6neEGR90AoIHyvLctOaQCNokZB7o8M2bfaQ6+ibmryjjhf1Fgilsn+KuuyEh+otQtmZzTVQ3Nbw5K1mvdixxCHP3/YHQwqHMKKs+tlCL53YvDOO7muGId8b+YhK2pDqTZDnHBXtejIqgY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=c61rSPv3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="c61rSPv3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7EB7C4CEEB; Tue, 16 Sep 2025 04:07:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1757995676; bh=RKJUVCWvFwzjN/Q37Y733wtl79nGCMwDcafr97JrFio=; h=Date:To:From:Subject:From; b=c61rSPv3ZXZcXDIcem0w2sUTWdirq+QDuvSY31bhfgUsi1UYf175pPKVJep28b5ap XieBd08AfEnNUyolgr+ituI9wi54F4tiWUT/mv14RtoD9s68BSQKDIOkSQchBoL4d8 YOTM9HuBYY01Mg3x6LZfDcllf98foHvOB8nLuXrg= Date: Mon, 15 Sep 2025 21:07:56 -0700 To: mm-commits@vger.kernel.org,mjguzik@gmail.com,jirislaby@kernel.org,brauner@kernel.org,oleg@redhat.com,akpm@linux-foundation.org From: Andrew Morton Subject: + fix-the-wrong-comment-on-task_lock-nesting-with-tasklist_lock.patch added to mm-nonmm-unstable branch Message-Id: <20250916040756.C7EB7C4CEEB@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: sched/task.h: fix the wrong comment on task_lock() nesting with tasklist_lock has been added to the -mm mm-nonmm-unstable branch. Its filename is fix-the-wrong-comment-on-task_lock-nesting-with-tasklist_lock.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fix-the-wrong-comment-on-task_lock-nesting-with-tasklist_lock.patch This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Oleg Nesterov Subject: sched/task.h: fix the wrong comment on task_lock() nesting with tasklist_lock Date: Sun, 14 Sep 2025 13:09:08 +0200 The ancient comment above task_lock() states that it can be nested outside of read_lock(&tasklist_lock), but this is no longer true: CPU_0 CPU_1 CPU_2 task_lock() read_lock(tasklist) write_lock_irq(tasklist) read_lock(tasklist) task_lock() Unless CPU_0 calls read_lock() in IRQ context, queued_read_lock_slowpath() won't get the lock immediately, it will spin waiting for the pending writer on CPU_2, resulting in a deadlock. Link: https://lkml.kernel.org/r/20250914110908.GA18769@redhat.com Signed-off-by: Oleg Nesterov Cc: Christian Brauner Cc: Jiri Slaby Cc: Mateusz Guzik Signed-off-by: Andrew Morton --- include/linux/sched/task.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) --- a/include/linux/sched/task.h~fix-the-wrong-comment-on-task_lock-nesting-with-tasklist_lock +++ a/include/linux/sched/task.h @@ -210,9 +210,8 @@ static inline struct vm_struct *task_sta * pins the final release of task.io_context. Also protects ->cpuset and * ->cgroup.subsys[]. And ->vfork_done. And ->sysvshm.shm_clist. * - * Nests both inside and outside of read_lock(&tasklist_lock). - * It must not be nested with write_lock_irq(&tasklist_lock), - * neither inside nor outside. + * Nests inside of read_lock(&tasklist_lock). It must not be nested with + * write_lock_irq(&tasklist_lock), neither inside nor outside. */ static inline void task_lock(struct task_struct *p) { _ Patches currently in -mm which might be from oleg@redhat.com are fix-the-wrong-comment-on-task_lock-nesting-with-tasklist_lock.patch fix-the-racy-usage-of-task_locktsk-group_leader-in-sys_prlimit64-paths.patch