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Date:   Tue, 8 Oct 2019 14:36:01 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Bruce Ashfield <bruce.ashfield@gmail.com>
Cc:     Roman Gushchin <guro@fb.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "tj@kernel.org" <tj@kernel.org>,
        Richard Purdie <richard.purdie@linuxfoundation.org>
Subject: Re: ptrace/strace and freezer oddities and v5.2+ kernels
Message-ID: <20191008123601.GA28621@redhat.com>
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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.

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 {