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[209.132.183.28]) by mx.google.com with ESMTPS id a3si3958839qvj.12.2019.03.22.04.49.26 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 Mar 2019 04:49:26 -0700 (PDT) Received-SPF: pass (google.com: domain of oleg@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of oleg@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 758D8A12A7; Fri, 22 Mar 2019 11:49:25 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.32]) by smtp.corp.redhat.com (Postfix) with SMTP id 2DD3417160; Fri, 22 Mar 2019 11:49:20 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 22 Mar 2019 12:49:23 +0100 (CET) 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 , linux-kernel@vger.kernel.org, linux-mm@kvack.org, selinux@vger.kernel.org, Paul Moore , Stephen Smalley , Eric Paris , "Peter Zijlstra (Intel)" Subject: Re: [PATCH 0/4] Signal: Fix hard lockup problem in flush_sigqueue() Message-ID: <20190322114917.GC28876@redhat.com> References: <20190321214512.11524-1-longman@redhat.com> <20190322101535.GA10344@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190322101535.GA10344@bombadil.infradead.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Fri, 22 Mar 2019 11:49:25 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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. Oleg.