locking/percpu-rwsem: Fold __percpu_up_read()

Now that __percpu_up_read() is only ever used from percpu_up_read()
merge them, it's a small function.

Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lkml.kernel.org/r/20200131151540.212415454@infradead.org

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index f5ecf6a..5e033fe 100644 (file)
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -43,7 +43,6 @@ is_static struct percpu_rw_semaphore name = {                         \
        __DEFINE_PERCPU_RWSEM(name, static)
 
 extern bool __percpu_down_read(struct percpu_rw_semaphore *, bool);
-extern void __percpu_up_read(struct percpu_rw_semaphore *);
 
 static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
 {
@@ -103,10 +102,22 @@ static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
        /*
         * Same as in percpu_down_read().
         */
-       if (likely(rcu_sync_is_idle(&sem->rss)))
+       if (likely(rcu_sync_is_idle(&sem->rss))) {
                __this_cpu_dec(*sem->read_count);
-       else
-               __percpu_up_read(sem); /* Unconditional memory barrier */
+       } else {
+               /*
+                * slowpath; reader will only ever wake a single blocked
+                * writer.
+                */
+               smp_mb(); /* B matches C */
+               /*
+                * In other words, if they see our decrement (presumably to
+                * aggregate zero, as that is the only time it matters) they
+                * will also see our critical section.
+                */
+               __this_cpu_dec(*sem->read_count);
+               rcuwait_wake_up(&sem->writer);
+       }
        preempt_enable();
 }
 

diff --git a/kernel/exit.c b/kernel/exit.c
index 2833ffb..f64a8f9 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -258,6 +258,7 @@ void rcuwait_wake_up(struct rcuwait *w)
                wake_up_process(task);
        rcu_read_unlock();
 }
+EXPORT_SYMBOL_GPL(rcuwait_wake_up);
 
 /*
  * Determine if a process group is "orphaned", according to the POSIX

diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index a136677..8048a9a 100644 (file)
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -177,21 +177,6 @@ bool __percpu_down_read(struct percpu_rw_semaphore *sem, bool try)
 }
 EXPORT_SYMBOL_GPL(__percpu_down_read);
 
-void __percpu_up_read(struct percpu_rw_semaphore *sem)
-{
-       smp_mb(); /* B matches C */
-       /*
-        * In other words, if they see our decrement (presumably to aggregate
-        * zero, as that is the only time it matters) they will also see our
-        * critical section.
-        */
-       __this_cpu_dec(*sem->read_count);
-
-       /* Prod writer to re-evaluate readers_active_check() */
-       rcuwait_wake_up(&sem->writer);
-}
-EXPORT_SYMBOL_GPL(__percpu_up_read);
-
 #define per_cpu_sum(var)                                               \
 ({                                                                     \
        typeof(var) __sum = 0;                                          \