linux-kernel - Re: ptrace/strace and freezer oddities and v5.2+ kernels

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Message-ID: <20191008172706.GA9392@tower.DHCP.thefacebook.com>
Date:   Tue, 8 Oct 2019 17:27:10 +0000
From:   Roman Gushchin <guro@...com>
To:     Oleg Nesterov <oleg@...hat.com>
CC:     Bruce Ashfield <bruce.ashfield@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tj@...nel.org" <tj@...nel.org>,
        "Richard Purdie" <richard.purdie@...uxfoundation.org>
Subject: Re: ptrace/strace and freezer oddities and v5.2+ kernels

On Tue, Oct 08, 2019 at 02:36:01PM +0200, Oleg Nesterov wrote:
> On 10/08, Bruce Ashfield wrote:
> >
> > So I've been looking through the config delta's and late last night, I was
> > able to move the runtime back to a failed 4 minute state by adding the
> > CONFIG_PREEMPT settings that we have by default in our reference
> > kernel.

Ah, yeah, I don't have CONFIG_PREEMPT on any of my machines.
Good catch, Bruce!

> 
> Aha... Can you try the patch below?
> 
> Oleg.
> 
> --- x/kernel/signal.c
> +++ x/kernel/signal.c
> @@ -2205,8 +2205,8 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
>  		 */
>  		preempt_disable();
>  		read_unlock(&tasklist_lock);
> -		preempt_enable_no_resched();
>  		cgroup_enter_frozen();
> +		preempt_enable_no_resched();
>  		freezable_schedule();
>  		cgroup_leave_frozen(true);
>  	} else {
> 

That was fast! Thank you, Oleg!