Messages in this thread Patch in this message | | | Date | Wed, 30 Apr 2014 20:47:58 -0400 | From | Steven Rostedt <> | Subject | [PATCH RT 1/3] rt: Move migrate_disable up in trylocks |
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3.12.15-rt26-rc1 stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt <rostedt@goodmis.org>
The changes to move the migrate_disable() down in the trylocks() caused race conditions to appear in the cpu hotplug code. The migrate disables must be done before any of the rtmutexes are taken, otherwise a lock may be held that prevents hotplug from moving forward.
Link: http://lkml.kernel.org/r/20140429201308.63292691@gandalf.local.home
Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Nicholas Mc Guire <der.herr@hofr.at> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: linux-rt-users <linux-rt-users@vger.kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: John Kacur <jkacur@redhat.com> Cc: Clark Williams <williams@redhat.com> --- kernel/rt.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/kernel/rt.c b/kernel/rt.c index 5d17727..5f44def 100644 --- a/kernel/rt.c +++ b/kernel/rt.c @@ -180,12 +180,15 @@ EXPORT_SYMBOL(_mutex_unlock); */ int __lockfunc rt_write_trylock(rwlock_t *rwlock) { - int ret = rt_mutex_trylock(&rwlock->lock); + int ret; + + migrate_disable(); + ret = rt_mutex_trylock(&rwlock->lock); - if (ret) { + if (ret) rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_); - migrate_disable(); - } + else + migrate_enable(); return ret; } @@ -212,11 +215,12 @@ int __lockfunc rt_read_trylock(rwlock_t *rwlock) * write locked. */ if (rt_mutex_owner(lock) != current) { + migrate_disable(); ret = rt_mutex_trylock(lock); - if (ret) { + if (ret) rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_); - migrate_disable(); - } + else + migrate_enable(); } else if (!rwlock->read_depth) { ret = 0; } @@ -245,8 +249,8 @@ void __lockfunc rt_read_lock(rwlock_t *rwlock) */ if (rt_mutex_owner(lock) != current) { rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_); - __rt_spin_lock(lock); migrate_disable(); + __rt_spin_lock(lock); } rwlock->read_depth++; } -- 1.8.5.3
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