Merge remote-tracking branch 'asoc/topic/adsp' into asoc-next

[firefly-linux-kernel-4.4.55.git] / include / linux / percpu-rwsem.h

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index cf80f7e5277f14dcce2931232a808e592344e7aa..250a4acddb2b8975a6c8278a3c5b1d803f36b585 100644 (file)
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -12,34 +12,27 @@ struct percpu_rw_semaphore {
        struct mutex mtx;
 };
 
+#define light_mb()     barrier()
+#define heavy_mb()     synchronize_sched()
+
 static inline void percpu_down_read(struct percpu_rw_semaphore *p)
 {
-       rcu_read_lock();
+       rcu_read_lock_sched();
        if (unlikely(p->locked)) {
-               rcu_read_unlock();
+               rcu_read_unlock_sched();
                mutex_lock(&p->mtx);
                this_cpu_inc(*p->counters);
                mutex_unlock(&p->mtx);
                return;
        }
        this_cpu_inc(*p->counters);
-       rcu_read_unlock();
+       rcu_read_unlock_sched();
+       light_mb(); /* A, between read of p->locked and read of data, paired with D */
 }
 
 static inline void percpu_up_read(struct percpu_rw_semaphore *p)
 {
-       /*
-        * On X86, write operation in this_cpu_dec serves as a memory unlock
-        * barrier (i.e. memory accesses may be moved before the write, but
-        * no memory accesses are moved past the write).
-        * On other architectures this may not be the case, so we need smp_mb()
-        * there.
-        */
-#if defined(CONFIG_X86) && (!defined(CONFIG_X86_PPRO_FENCE) && !defined(CONFIG_X86_OOSTORE))
-       barrier();
-#else
-       smp_mb();
-#endif
+       light_mb(); /* B, between read of the data and write to p->counter, paired with C */
        this_cpu_dec(*p->counters);
 }
 
@@ -58,14 +51,15 @@ static inline void percpu_down_write(struct percpu_rw_semaphore *p)
 {
        mutex_lock(&p->mtx);
        p->locked = true;
-       synchronize_rcu();
+       synchronize_sched(); /* make sure that all readers exit the rcu_read_lock_sched region */
        while (__percpu_count(p->counters))
                msleep(1);
-       smp_rmb(); /* paired with smp_mb() in percpu_sem_up_read() */
+       heavy_mb(); /* C, between read of p->counter and write to data, paired with B */
 }
 
 static inline void percpu_up_write(struct percpu_rw_semaphore *p)
 {
+       heavy_mb(); /* D, between write to data and write to p->locked, paired with A */
        p->locked = false;
        mutex_unlock(&p->mtx);
 }