From: Oleg Nesterov <oleg@redhat.com>
To: peterz@infradead.org
Cc: Jiri Slaby <jirislaby@kernel.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
christian@brauner.io, "Eric W. Biederman" <ebiederm@xmission.com>,
Linux kernel mailing list <linux-kernel@vger.kernel.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 16:02:24 +0200 [thread overview]
Message-ID: <20200720140224.GD6612@redhat.com> (raw)
In-Reply-To: <20200720105924.GE43129@hirez.programming.kicks-ass.net>
On 07/20, Peter Zijlstra wrote:
>
> Also, is there any way to not have ptrace do this?
Well, we need to ensure that even SIGKILL can't wake the tracee up while
debugger plays with its registers/etc.
> How performance
> critical is this ptrace path?
This is a slow path.
We can probably change ptrace_check_attach() to call ptrace_freeze_traced()
after wait_task_inactive(), but I would like to not do this... Because we
actually want to avoid wait_task_inactive() when possible.
Perhaps ptrace_freeze_traced() can __task_rq_lock() to avoid the race with
__schedule() ? No, it reads prev_state before rq_lock().
> Because I really hate having to add code
> to __schedule() to deal with this horrible thing.
Oh yes, I agree.
I have to admit, I do not understand the usage of prev_state in schedule(),
it looks really, really subtle...
Oleg.
next prev parent reply other threads:[~2020-07-20 14:02 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 10:45 5.8-rc*: kernel BUG at kernel/signal.c:1917 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
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 [this message]
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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