Date: Wed, 30 Jul 2008 20:22:21 +0000 (UTC) From: Ed Maste <emaste@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/kern kern_timeout.c Message-ID: <200807302022.m6UKMTf4017190@repoman.freebsd.org>
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emaste 2008-07-30 20:22:21 UTC
FreeBSD src repository
Modified files: (Branch: RELENG_6)
sys/kern kern_timeout.c
Log:
SVN rev 181012 on 2008-07-30 20:22:21Z by emaste
MFC improved and simplified callout_drain logic and improved ktr(4)
logging.
r155957:
Use the recently added msleep_spin() function to simplify the
callout_drain() logic. We no longer need a separate non-spin mutex to
do sleep/wakeup with, instead we can now just use the one spin mutex
to manage all the callout functionality.
r163246:
Improve ktr(4) logging for callout(9) subsystem. Log all inserts and
removals, including failures, into the callwheel.
r171053:
Fix an old standing LOR between callout_lock and sleepqueues chain
(which could lead to a deadlock).
- sleepq_set_timeout acquires callout_lock (via callout_reset()) only
with sleepq chain lock held
- msleep_spin in _callout_stop_safe lock the sleepqueue chain with
callout_lock held
In order to solve this don't use msleep_spin in _callout_stop_safe()
but use directly sleepqueues as inline msleep_spin code. Rearrange the
wakeup path in order to have it consistent too.
r172025:
Close a race that snuck in with the recent changes to fix a LOR
between the callout_lock spin lock and the sleepqueue spin locks.
In the fix, callout_drain() has to drop the callout_lock so it can
acquire the sleepqueue lock. The state of the callout can change
while the callout_lock is held however (for example, it can be
rescheduled via callout_reset()). The previous code assumed that the
only state change that could happen is that the callout could finish
executing. This change alters callout_drain() to effectively restart
and recheck everything after it acquires the sleepqueue lock thus
handling all the possible states that the callout could be in after
any changes while callout_lock was dropped.
Revision Changes Path
1.97.2.3 +106 -60 src/sys/kern/kern_timeout.c
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