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 <peterz@infradead.org>
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 <jason.low2@hp.com>
Link: http://lkml.kernel.org/n/tip-62hcl5wxydmjzd182zhvk89m@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index dc3d6f2bbe2a..2670b84067d6 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -53,7 +53,7 @@ __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
         INIT_LIST_HEAD(&lock->wait_list);
         mutex_clear_owner(lock);
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
-        lock->mcs_lock = NULL;
+        lock->osq = NULL;
 #endif
 
         debug_mutex_init(lock, name, key);
@@ -403,7 +403,9 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
         if (!mutex_can_spin_on_owner(lock))
                 goto slowpath;
 
-        mcs_spin_lock(&lock->mcs_lock, &node);
+        if (!osq_lock(&lock->osq))
+                goto slowpath;
+
         for (;;) {
                 struct task_struct *owner;
 
@@ -442,7 +444,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                         }
 
                         mutex_set_owner(lock);
-                        mcs_spin_unlock(&lock->mcs_lock, &node);
+                        osq_unlock(&lock->osq);
                         preempt_enable();
                         return 0;
                 }
@@ -464,7 +466,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                  */
                 arch_mutex_cpu_relax();
         }
-        mcs_spin_unlock(&lock->mcs_lock, &node);
+        osq_unlock(&lock->osq);
 slowpath:
 #endif
         spin_lock_mutex(&lock->wait_lock, flags);