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-rw-r--r--kernel/mutex-debug.c2
-rw-r--r--kernel/mutex-debug.h2
-rw-r--r--kernel/mutex.c2
-rw-r--r--kernel/mutex.h2
-rw-r--r--kernel/sched.c83
5 files changed, 37 insertions, 54 deletions
diff --git a/kernel/mutex-debug.c b/kernel/mutex-debug.c
index ec815a960b5..73da83aff41 100644
--- a/kernel/mutex-debug.c
+++ b/kernel/mutex-debug.c
@@ -75,7 +75,7 @@ void debug_mutex_unlock(struct mutex *lock)
return;
DEBUG_LOCKS_WARN_ON(lock->magic != lock);
- DEBUG_LOCKS_WARN_ON(lock->owner != current_thread_info());
+ DEBUG_LOCKS_WARN_ON(lock->owner != current);
DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
mutex_clear_owner(lock);
}
diff --git a/kernel/mutex-debug.h b/kernel/mutex-debug.h
index 57d527a16f9..0799fd3e4cf 100644
--- a/kernel/mutex-debug.h
+++ b/kernel/mutex-debug.h
@@ -29,7 +29,7 @@ extern void debug_mutex_init(struct mutex *lock, const char *name,
static inline void mutex_set_owner(struct mutex *lock)
{
- lock->owner = current_thread_info();
+ lock->owner = current;
}
static inline void mutex_clear_owner(struct mutex *lock)
diff --git a/kernel/mutex.c b/kernel/mutex.c
index c4195fa9890..fe4706cb0c5 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -160,7 +160,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
*/
for (;;) {
- struct thread_info *owner;
+ struct task_struct *owner;
/*
* If we own the BKL, then don't spin. The owner of
diff --git a/kernel/mutex.h b/kernel/mutex.h
index 67578ca48f9..4115fbf83b1 100644
--- a/kernel/mutex.h
+++ b/kernel/mutex.h
@@ -19,7 +19,7 @@
#ifdef CONFIG_SMP
static inline void mutex_set_owner(struct mutex *lock)
{
- lock->owner = current_thread_info();
+ lock->owner = current;
}
static inline void mutex_clear_owner(struct mutex *lock)
diff --git a/kernel/sched.c b/kernel/sched.c
index cd2593e1a3e..55cc50323ce 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4173,70 +4173,53 @@ need_resched:
EXPORT_SYMBOL(schedule);
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
-/*
- * Look out! "owner" is an entirely speculative pointer
- * access and not reliable.
- */
-int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
-{
- unsigned int cpu;
- struct rq *rq;
- if (!sched_feat(OWNER_SPIN))
- return 0;
+static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
+{
+ bool ret = false;
-#ifdef CONFIG_DEBUG_PAGEALLOC
- /*
- * Need to access the cpu field knowing that
- * DEBUG_PAGEALLOC could have unmapped it if
- * the mutex owner just released it and exited.
- */
- if (probe_kernel_address(&owner->cpu, cpu))
- return 0;
-#else
- cpu = owner->cpu;
-#endif
+ rcu_read_lock();
+ if (lock->owner != owner)
+ goto fail;
/*
- * Even if the access succeeded (likely case),
- * the cpu field may no longer be valid.
+ * Ensure we emit the owner->on_cpu, dereference _after_ checking
+ * lock->owner still matches owner, if that fails, owner might
+ * point to free()d memory, if it still matches, the rcu_read_lock()
+ * ensures the memory stays valid.
*/
- if (cpu >= nr_cpumask_bits)
- return 0;
+ barrier();
- /*
- * We need to validate that we can do a
- * get_cpu() and that we have the percpu area.
- */
- if (!cpu_online(cpu))
- return 0;
+ ret = owner->on_cpu;
+fail:
+ rcu_read_unlock();
- rq = cpu_rq(cpu);
+ return ret;
+}
- for (;;) {
- /*
- * Owner changed, break to re-assess state.
- */
- if (lock->owner != owner) {
- /*
- * If the lock has switched to a different owner,
- * we likely have heavy contention. Return 0 to quit
- * optimistic spinning and not contend further:
- */
- if (lock->owner)
- return 0;
- break;
- }
+/*
+ * Look out! "owner" is an entirely speculative pointer
+ * access and not reliable.
+ */
+int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
+{
+ if (!sched_feat(OWNER_SPIN))
+ return 0;
- /*
- * Is that owner really running on that cpu?
- */
- if (task_thread_info(rq->curr) != owner || need_resched())
+ while (owner_running(lock, owner)) {
+ if (need_resched())
return 0;
arch_mutex_cpu_relax();
}
+ /*
+ * If the owner changed to another task there is likely
+ * heavy contention, stop spinning.
+ */
+ if (lock->owner)
+ return 0;
+
return 1;
}
#endif