From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Guy Briggs Subject: [PATCH 5/8] audit: efficiency fix 2: request exclusive wait since all need same resource Date: Wed, 18 Sep 2013 15:06:50 -0400 Message-ID: <5c2035525f6bf06dcaa24a5922071d2f4e4e495e.1379530867.git.rgb@redhat.com> References: <20130917152842.51158606ed46ec67b97b4448@linux-foundation.org> Return-path: In-Reply-To: <20130917152842.51158606ed46ec67b97b4448@linux-foundation.org> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org To: linux-audit@redhat.com, linux-kernel@vger.kernel.org Cc: Richard Guy Briggs , Steve Grubb , Eric Paris , Konstantin Khlebnikov , Andrew Morton , Dan Duval , Chuck Anderson , Guy Streeter , Oleg Nesterov List-Id: linux-audit@redhat.com author: Dan Duval These and similar errors were seen on a patched 3.8 kernel when the audit subsystem was overrun during boot: udevd[876]: worker [887] unexpectedly returned with status 0x0100 udevd[876]: worker [887] failed while handling '/devices/pci0000:00/0000:00:03.0/0000:40:00.0' udevd[876]: worker [880] unexpectedly returned with status 0x0100 udevd[876]: worker [880] failed while handling '/devices/LNXSYSTM:00/LNXPWRBN:00/input/input1/event1' udevadm settle - timeout of 180 seconds reached, the event queue contains: /sys/devices/LNXSYSTM:00/LNXPWRBN:00/input/input1/event1 (3995) /sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/INT3F0D:00 (4034) audit: audit_backlog=258 > audit_backlog_limit=256 audit: audit_lost=1 audit_rate_limit=0 audit_backlog_limit=256 The change below increases the efficiency of the audit code and prevents it from being overrun: Use add_wait_queue_exclusive() in wait_for_auditd() to put the thread on the wait queue. When kauditd dequeues an skb, all of the waiting threads are waiting for the same resource, but only one is going to get it, so there's no need to wake up more than one waiter. See: https://lkml.org/lkml/2013/9/2/479 Signed-off-by: Dan Duval Signed-off-by: Chuck Anderson Signed-off-by: Richard Guy Briggs --- kernel/audit.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/audit.c b/kernel/audit.c index 25fab2d..990d02f 100644 --- a/kernel/audit.c +++ b/kernel/audit.c @@ -1061,7 +1061,7 @@ static unsigned long wait_for_auditd(unsigned long sleep_time) unsigned long timeout = sleep_time; DECLARE_WAITQUEUE(wait, current); set_current_state(TASK_UNINTERRUPTIBLE); - add_wait_queue(&audit_backlog_wait, &wait); + add_wait_queue_exclusive(&audit_backlog_wait, &wait); if (audit_backlog_limit && skb_queue_len(&audit_skb_queue) > audit_backlog_limit) -- 1.7.1