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[209.132.183.28]) by mx.google.com with ESMTPS id c6si3858641qtc.307.2019.03.21.14.45.37 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Mar 2019 14:45:37 -0700 (PDT) Received-SPF: pass (google.com: domain of longman@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 longman@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=longman@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 DA86A59443; Thu, 21 Mar 2019 21:45:35 +0000 (UTC) Received: from llong.com (dhcp-17-47.bos.redhat.com [10.18.17.47]) by smtp.corp.redhat.com (Postfix) with ESMTP id 845765C8BD; Thu, 21 Mar 2019 21:45:27 +0000 (UTC) From: Waiman Long To: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, selinux@vger.kernel.org, Paul Moore , Stephen Smalley , Eric Paris , "Peter Zijlstra (Intel)" , Oleg Nesterov , Waiman Long Subject: [PATCH 0/4] Signal: Fix hard lockup problem in flush_sigqueue() Date: Thu, 21 Mar 2019 17:45:08 -0400 Message-Id: <20190321214512.11524-1-longman@redhat.com> 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 [10.5.110.39]); Thu, 21 Mar 2019 21:45:36 +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: 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). release_task() => flush_sigqueue() The lockup condition can be reproduced on a large system with a lot of memory and relatively slow CPUs running LTP's sigqueue_9-1 test on a debug kernel. This patchset tries to mitigate this problem by introducing a new kernel memory freeing queue mechanism modelled after the wake_q mechanism for waking up tasks. Then flush_sigqueue() and release_task() are modified to use the freeing queue mechanism to defer the actual memory object freeing until after releasing the tasklist_lock and with irq re-enabled. With the patchset applied, the hard lockup problem was no longer reproducible on the debug kernel. Waiman Long (4): mm: Implement kmem objects freeing queue signal: Make flush_sigqueue() use free_q to release memory signal: Add free_uid_to_q() mm: Do periodic rescheduling when freeing objects in kmem_free_up_q() include/linux/sched/user.h | 3 +++ include/linux/signal.h | 4 ++- include/linux/slab.h | 28 +++++++++++++++++++++ kernel/exit.c | 12 ++++++--- kernel/signal.c | 29 +++++++++++++--------- kernel/user.c | 17 ++++++++++--- mm/slab_common.c | 50 ++++++++++++++++++++++++++++++++++++++ security/selinux/hooks.c | 8 ++++-- 8 files changed, 128 insertions(+), 23 deletions(-) -- 2.18.1