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* locking/mutexes: Return false if task need_resched() in ↵Jason Low2014-03-111-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | mutex_can_spin_on_owner() The mutex_can_spin_on_owner() function should also return false if the task needs to be rescheduled to avoid entering the MCS queue when it needs to reschedule. Signed-off-by: Jason Low <jason.low2@hp.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Waiman.Long@hp.com Cc: torvalds@linux-foundation.org Cc: tglx@linutronix.de Cc: riel@redhat.com Cc: akpm@linux-foundation.org Cc: davidlohr@hp.com Cc: hpa@zytor.com Cc: andi@firstfloor.org Cc: aswin@hp.com Cc: scott.norton@hp.com Cc: chegu_vinod@hp.com Cc: paulmck@linux.vnet.ibm.com Link: http://lkml.kernel.org/r/1390936396-3962-2-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking: Move mcs_spinlock.h into kernel/locking/Peter Zijlstra2014-03-111-1/+1
| | | | | | | | | | | | | | The mcs_spinlock code is not meant (or suitable) as a generic locking primitive, therefore take it away from the normal includes and place it in kernel/locking/. This way the locking primitives implemented there can use it as part of their implementation but we do not risk it getting used inapropriately. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-byirmpamgr7h25m5kyavwpzx@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutexes/mcs: Restructure the MCS lock defines and locking code into ↵Tim Chen2014-01-281-61/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | its own file We will need the MCS lock code for doing optimistic spinning for rwsem and queued rwlock. Extracting the MCS code from mutex.c and put into its own file allow us to reuse this code easily. We also inline mcs_spin_lock and mcs_spin_unlock functions for better efficiency. Note that using the smp_load_acquire/smp_store_release pair used in mcs_lock and mcs_unlock is not sufficient to form a full memory barrier across cpus for many architectures (except x86). For applications that absolutely need a full barrier across multiple cpus with mcs_unlock and mcs_lock pair, smp_mb__after_unlock_lock() should be used after mcs_lock. Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Davidlohr Bueso <davidlohr@hp.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1390347360.3138.63.camel@schen9-DESK Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/mutexes/mcs: Correct barrier usageWaiman Long2014-01-281-5/+13
| | | | | | | | | | | | | | | | | | | | | | | This patch corrects the way memory barriers are used in the MCS lock with smp_load_acquire and smp_store_release fucnctions. The previous barriers could leak critical sections if mcs lock is used by itself. It is not a problem when mcs lock is embedded in mutex but will be an issue when the mcs_lock is used elsewhere. The patch removes the incorrect barriers and put in correct barriers with the pair of functions smp_load_acquire and smp_store_release. Suggested-by: Michel Lespinasse <walken@google.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Waiman Long <Waiman.Long@hp.com> Signed-off-by: Jason Low <jason.low2@hp.com> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1390347353.3138.62.camel@schen9-DESK Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking/doc: Update references to kernel/mutex.cPeter Zijlstra2013-11-111-1/+1
| | | | | | | | | | | | | Fix this docbook error: >> docproc: kernel/mutex.c: No such file or directory by updating the stale references to kernel/mutex.c. Reported-by: fengguang.wu@intel.com Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-34pikw1tlsskj65rrt5iusrq@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* locking: Move the mutex code to kernel/locking/Peter Zijlstra2013-11-061-0/+960
Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-1ditvncg30dgbpvrz2bxfmke@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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