1 files changed, 32 insertions, 62 deletions

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 4dd6e4c219de..14fe72cc8ce7 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -25,6 +25,7 @@
 #include <linux/spinlock.h>
 #include <linux/interrupt.h>
 #include <linux/debug_locks.h>
+#include "mcs_spinlock.h"
 
 /*
  * In the DEBUG case we are using the "NULL fastpath" for mutexes,
@@ -33,6 +34,13 @@
 #ifdef CONFIG_DEBUG_MUTEXES
 # include "mutex-debug.h"
 # include <asm-generic/mutex-null.h>
+/*
+ * Must be 0 for the debug case so we do not do the unlock outside of the
+ * wait_lock region. debug_mutex_unlock() will do the actual unlock in this
+ * case.
+ */
+# undef __mutex_slowpath_needs_to_unlock
+# define  __mutex_slowpath_needs_to_unlock()    0
 #else
 # include "mutex.h"
 # include <asm/mutex.h>
@@ -52,7 +60,7 @@ __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->spin_mlock = NULL;
+        lock->osq = NULL;
 #endif
 
         debug_mutex_init(lock, name, key);
@@ -111,54 +119,7 @@ EXPORT_SYMBOL(mutex_lock);
  * more or less simultaneously, the spinners need to acquire a MCS lock
  * first before spinning on the owner field.
  *
- * We don't inline mspin_lock() so that perf can correctly account for the
- * time spent in this lock function.
  */
-struct mspin_node {
-        struct mspin_node *next ;
-        int               locked;       /* 1 if lock acquired */
-};
-#define MLOCK(mutex)    ((struct mspin_node **)&((mutex)->spin_mlock))
-
-static noinline
-void mspin_lock(struct mspin_node **lock, struct mspin_node *node)
-{
-        struct mspin_node *prev;
-
-        /* Init node */
-        node->locked = 0;
-        node->next   = NULL;
-
-        prev = xchg(lock, node);
-        if (likely(prev == NULL)) {
-                /* Lock acquired */
-                node->locked = 1;
-                return;
-        }
-        ACCESS_ONCE(prev->next) = node;
-        smp_wmb();
-        /* Wait until the lock holder passes the lock down */
-        while (!ACCESS_ONCE(node->locked))
-                arch_mutex_cpu_relax();
-}
-
-static void mspin_unlock(struct mspin_node **lock, struct mspin_node *node)
-{
-        struct mspin_node *next = ACCESS_ONCE(node->next);
-
-        if (likely(!next)) {
-                /*
-                 * Release the lock by setting it to NULL
-                 */
-                if (cmpxchg(lock, node, NULL) == node)
-                        return;
-                /* Wait until the next pointer is set */
-                while (!(next = ACCESS_ONCE(node->next)))
-                        arch_mutex_cpu_relax();
-        }
-        ACCESS_ONCE(next->locked) = 1;
-        smp_wmb();
-}
 
 /*
  * Mutex spinning code migrated from kernel/sched/core.c
@@ -212,6 +173,9 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock)
         struct task_struct *owner;
         int retval = 1;
 
+        if (need_resched())
+                return 0;
+
         rcu_read_lock();
         owner = ACCESS_ONCE(lock->owner);
         if (owner)
@@ -446,9 +410,11 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
         if (!mutex_can_spin_on_owner(lock))
                 goto slowpath;
 
+        if (!osq_lock(&lock->osq))
+                goto slowpath;
+
         for (;;) {
                 struct task_struct *owner;
-                struct mspin_node  node;
 
                 if (use_ww_ctx && ww_ctx->acquired > 0) {
                         struct ww_mutex *ww;
@@ -463,19 +429,16 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                          * performed the optimistic spinning cannot be done.
                          */
                         if (ACCESS_ONCE(ww->ctx))
-                                goto slowpath;
+                                break;
                 }
 
                 /*
                  * If there's an owner, wait for it to either
                  * release the lock or go to sleep.
                  */
-                mspin_lock(MLOCK(lock), &node);
                 owner = ACCESS_ONCE(lock->owner);
-                if (owner && !mutex_spin_on_owner(lock, owner)) {
-                        mspin_unlock(MLOCK(lock), &node);
-                        goto slowpath;
-                }
+                if (owner && !mutex_spin_on_owner(lock, owner))
+                        break;
 
                 if ((atomic_read(&lock->count) == 1) &&
                     (atomic_cmpxchg(&lock->count, 1, 0) == 1)) {
@@ -488,11 +451,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                         }
 
                         mutex_set_owner(lock);
-                        mspin_unlock(MLOCK(lock), &node);
+                        osq_unlock(&lock->osq);
                         preempt_enable();
                         return 0;
                 }
-                mspin_unlock(MLOCK(lock), &node);
 
                 /*
                  * When there's no owner, we might have preempted between the
@@ -501,7 +463,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                  * the owner complete.
                  */
                 if (!owner && (need_resched() || rt_task(task)))
-                        goto slowpath;
+                        break;
 
                 /*
                  * The cpu_relax() call is a compiler barrier which forces
@@ -511,7 +473,15 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
                  */
                 arch_mutex_cpu_relax();
         }
+        osq_unlock(&lock->osq);
 slowpath:
+        /*
+         * If we fell out of the spin path because of need_resched(),
+         * reschedule now, before we try-lock the mutex. This avoids getting
+         * scheduled out right after we obtained the mutex.
+         */
+        if (need_resched())
+                schedule_preempt_disabled();
 #endif
         spin_lock_mutex(&lock->wait_lock, flags);
 
@@ -717,10 +687,6 @@ __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
         struct mutex *lock = container_of(lock_count, struct mutex, count);
         unsigned long flags;
 
-        spin_lock_mutex(&lock->wait_lock, flags);
-        mutex_release(&lock->dep_map, nested, _RET_IP_);
-        debug_mutex_unlock(lock);
-
         /*
          * some architectures leave the lock unlocked in the fastpath failure
          * case, others need to leave it locked. In the later case we have to
@@ -729,6 +695,10 @@ __mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
         if (__mutex_slowpath_needs_to_unlock())
                 atomic_set(&lock->count, 1);
 
+        spin_lock_mutex(&lock->wait_lock, flags);
+        mutex_release(&lock->dep_map, nested, _RET_IP_);
+        debug_mutex_unlock(lock);
+
         if (!list_empty(&lock->wait_list)) {
                 /* get the first entry from the wait-list: */
                 struct mutex_waiter *waiter =