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Date:   Fri, 22 Mar 2019 12:49:17 +0100
From:   Oleg Nesterov <>
To:     Matthew Wilcox <>
Cc:     Waiman Long <>,
        Andrew Morton <>,
        Christoph Lameter <>,
        Pekka Enberg <>,
        David Rientjes <>,
        Joonsoo Kim <>,,,, Paul Moore <>,
        Stephen Smalley <>,
        Eric Paris <>,
        "Peter Zijlstra (Intel)" <>
Subject: Re: [PATCH 0/4] Signal: Fix hard lockup problem in flush_sigqueue()

On 03/22, Matthew Wilcox wrote:
> On Thu, Mar 21, 2019 at 05:45:08PM -0400, Waiman Long wrote:
> > It was found that if a process has accumulated sufficient number of
> > pending signals, the exiting of that process may cause its parent to
> > have hard lockup when running on a debug kernel with a slow memory
> > freeing path (like with KASAN enabled).
> I appreciate these are "reliable" signals, but why do we accumulate so
> many signals to a task which will never receive them?  Can we detect at
> signal delivery time that the task is going to die and avoid queueing
> them in the first place?

A task can block the signal and accumulate up to RLIMIT_SIGPENDING signals,
then it can exit.


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