From fb0527bd5ea99bfeb2dd91e3c1433ecf745d6b99 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 29 Jan 2014 12:51:42 +0100 Subject: locking/mutexes: Introduce cancelable MCS lock for adaptive spinning Since we want a task waiting for a mutex_lock() to go to sleep and reschedule on need_resched() we must be able to abort the mcs_spin_lock() around the adaptive spin. Therefore implement a cancelable mcs lock. Signed-off-by: Peter Zijlstra Cc: chegu_vinod@hp.com Cc: paulmck@linux.vnet.ibm.com 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: Jason Low Link: http://lkml.kernel.org/n/tip-62hcl5wxydmjzd182zhvk89m@git.kernel.org Signed-off-by: Ingo Molnar --- kernel/locking/mcs_spinlock.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'kernel/locking/mcs_spinlock.h') diff --git a/kernel/locking/mcs_spinlock.h b/kernel/locking/mcs_spinlock.h index f2a5c6360083..a2dbac4aca6b 100644 --- a/kernel/locking/mcs_spinlock.h +++ b/kernel/locking/mcs_spinlock.h @@ -111,4 +111,19 @@ void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node) arch_mcs_spin_unlock_contended(&next->locked); } +/* + * Cancellable version of the MCS lock above. + * + * Intended for adaptive spinning of sleeping locks: + * mutex_lock()/rwsem_down_{read,write}() etc. + */ + +struct optimistic_spin_queue { + struct optimistic_spin_queue *next, *prev; + int locked; /* 1 if lock acquired */ +}; + +extern bool osq_lock(struct optimistic_spin_queue **lock); +extern void osq_unlock(struct optimistic_spin_queue **lock); + #endif /* __LINUX_MCS_SPINLOCK_H */ -- cgit v1.2.3