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Date:   Fri, 22 Mar 2019 03:15:35 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Waiman Long <longman@redhat.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        selinux@vger.kernel.org, Paul Moore <paul@paul-moore.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Eric Paris <eparis@parisplace.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 0/4] Signal: Fix hard lockup problem in flush_sigqueue()
Message-ID: <20190322101535.GA10344@bombadil.infradead.org>
References: <20190321214512.11524-1-longman@redhat.com>
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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?