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From: Oleg Nesterov <oleg@redhat.com>
To: Jiri Slaby <jirislaby@kernel.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>,
	christian@brauner.io, "Eric W. Biederman" <ebiederm@xmission.com>,
	Linux kernel mailing list <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Mel Gorman <mgorman@suse.de>,
	Dave Jones <davej@codemonkey.org.uk>,
	Paul Gortmaker <paul.gortmaker@windriver.com>
Subject: Re: 5.8-rc*: kernel BUG at kernel/signal.c:1917
Date: Mon, 20 Jul 2020 08:43:26 +0200	[thread overview]
Message-ID: <20200720064326.GA6612@redhat.com> (raw)
In-Reply-To: <badcb9d5-f628-2be1-7a72-902cf08010bd@kernel.org>

On 07/20, Jiri Slaby wrote:
>
> You tackled it, we cherry-picked dbfb089d360 to our kernels. Ccing more
> people.

Thanks... so with this patch __schedule() does

	prev_state = prev->state;

	...

	if (!preempt && prev_state && prev_state == prev->state) {
		if (signal_pending_state(prev_state, prev)) {
			prev->state = TASK_RUNNING;
		} else {

and ptrace_freeze_traced() can change ->state in between. This means
that this task can return from __schedule() with ->state != RUNNING,
this can explain BUG_ON(task_is_stopped_or_traced) in do_notify_parent()
you reported.

Oleg.


  reply	other threads:[~2020-07-20  6:43 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-17 10:45 Jiri Slaby
2020-07-17 11:04 ` Jiri Slaby
2020-07-17 11:12   ` Christian Brauner
2020-07-18 13:05     ` Jiri Slaby
2020-07-17 12:26   ` Oleg Nesterov
2020-07-17 12:40     ` Oleg Nesterov
2020-07-18 12:28       ` Jiri Slaby
2020-07-18 17:14         ` Oleg Nesterov
2020-07-18 17:44           ` Christian Brauner
2020-07-20  5:44             ` Jiri Slaby
2020-07-20  6:43               ` Oleg Nesterov [this message]
2020-07-20  8:26                 ` Oleg Nesterov
2020-07-20  8:41                   ` Peter Zijlstra
2020-07-20 10:59                     ` peterz
2020-07-20 11:26                       ` peterz
2020-07-20 11:40                         ` Jiri Slaby
2020-07-20 12:20                         ` Valentin Schneider
2020-07-20 13:17                           ` peterz
2020-07-20 14:26                             ` Valentin Schneider
2020-07-20 12:57                         ` Christian Brauner
2020-07-20 14:05                         ` peterz
2020-07-20 14:02                       ` Oleg Nesterov
2020-07-20 14:21                         ` Peter Zijlstra
2020-07-20 14:39                           ` Oleg Nesterov
2020-07-20 15:35                             ` Oleg Nesterov
2020-07-20 15:38                               ` Peter Zijlstra
2020-07-21  4:52                           ` Paul Gortmaker
2020-07-21  8:37                             ` peterz
2020-07-21 12:13                               ` [PATCH] sched: Fix race against ptrace_freeze_trace() peterz
2020-07-21 14:29                                 ` Christian Brauner
2020-07-21 15:38                                 ` Oleg Nesterov
2020-07-21  9:14                           ` 5.8-rc*: kernel BUG at kernel/signal.c:1917 Valentin Schneider
     [not found]           ` <20200719072726.5892-1-hdanton@sina.com>
2020-07-19 18:23             ` Oleg Nesterov
2020-07-20  6:00           ` Jiri Slaby
2020-07-20  6:56             ` Oleg Nesterov

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