Date: Mon, 25 Jan 2010 22:25:20 -0800 From: Rob Farmer <rfarmer@predatorlabs.net> To: Attilio Rao <attilio@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r202889 - head/sys/kern Message-ID: <b025ceb71001252225r56d4b0c8qe4c6affe338e6f9f@mail.gmail.com> In-Reply-To: <201001231554.o0NFsMbx049837@svn.freebsd.org> References: <201001231554.o0NFsMbx049837@svn.freebsd.org>
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On Sat, Jan 23, 2010 at 7:54 AM, Attilio Rao <attilio@freebsd.org> wrote: > Author: attilio > Date: Sat Jan 23 15:54:21 2010 > New Revision: 202889 > URL: http://svn.freebsd.org/changeset/base/202889 > > Log: > - Fix a race in sched_switch() of sched_4bsd. > In the case of the thread being on a sleepqueue or a turnstile, the > sched_lock was acquired (without the aid of the td_lock interface) and > the td_lock was dropped. This was going to break locking rules on other > threads willing to access to the thread (via the td_lock interface) and > modify his flags (allowed as long as the container lock was different > by the one used in sched_switch). > In order to prevent this situation, while sched_lock is acquired there > the td_lock gets blocked. [0] > - Merge the ULE's internal function thread_block_switch() into the global > thread_lock_block() and make the former semantic as the default for > thread_lock_block(). This means that thread_lock_block() will not > disable interrupts when called (and consequently thread_unlock_block() > will not re-enabled them when called). This should be done manually > when necessary. > Note, however, that ULE's thread_unblock_switch() is not reaped > because it does reflect a difference in semantic due in ULE (the > td_lock may not be necessarilly still blocked_lock when calling this). > While asymmetric, it does describe a remarkable difference in semantic > that is good to keep in mind. > > [0] Reported by: Kohji Okuno > <okuno dot kohji at jp dot panasonic dot com> > Tested by: Giovanni Trematerra > <giovanni dot trematerra at gmail dot com> > MFC: 2 weeks > > Modified: > head/sys/kern/kern_mutex.c > head/sys/kern/sched_4bsd.c > head/sys/kern/sched_ule.c Hi, This commit seems to be causing me a kernel panic on sparc64 - details are in PR 143215. Could you take a look before MFCing this? Thanks, -- Rob Farmer
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