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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id v198si3958763pgb.204.2019.03.22.03.16.01 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 22 Mar 2019 03:16:01 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=eHZqkMXu; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=nBJewWCbdaJ5X4iQT6hRh0j0tFDuXREWOR4IbUJXZrw=; b=eHZqkMXuJaUupBq5agtV44k7F rlUiJ5cff+KL4dk+vjyMIFhLoq4JYR0WhK1ryKV7Nym63LnjGzMxBoF7HODFZyQuc1Zbb2hlBIlFH 77oZYullmVvDUschGOvwJxz1lqJf73QZPU364tHP/Wo7XGZICNCGIETJO/443iPrcSIWCock3qWYB 9nDvjnTkEZr6RyExdNRDyrQGRTu1GNBu4BevbyT/ZPs9HTctSQpu2/n+OiuQ19rVZT2sBOg2K/2B1 VVl/vIvTNpogP3pjWIta6k4fqBzVTHxeU0lc9vuMrv+O1eq+CzFe1WDPpeNaHB1W3Ep9RfU4VoXd/ KUnsSV5IA==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1h7HD6-0003yd-1c; Fri, 22 Mar 2019 10:15:36 +0000 Date: Fri, 22 Mar 2019 03:15:35 -0700 From: Matthew Wilcox To: Waiman Long Cc: 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)" , Oleg Nesterov 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190321214512.11524-1-longman@redhat.com> User-Agent: Mutt/1.9.2 (2017-12-15) 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 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?