2 files changed, 26 insertions, 5 deletions

diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
index d2146a4f833e..3e88c9a7d57f 100644
--- a/include/linux/percpu-rwsem.h
+++ b/include/linux/percpu-rwsem.h
@@ -5,6 +5,7 @@
 #include <linux/rwsem.h>
 #include <linux/percpu.h>
 #include <linux/wait.h>
+#include <linux/lockdep.h>
 
 struct percpu_rw_semaphore {
         unsigned int __percpu   *fast_read_ctr;
@@ -20,7 +21,14 @@ extern void percpu_up_read(struct percpu_rw_semaphore *);
 extern void percpu_down_write(struct percpu_rw_semaphore *);
 extern void percpu_up_write(struct percpu_rw_semaphore *);
 
-extern int percpu_init_rwsem(struct percpu_rw_semaphore *);
+extern int __percpu_init_rwsem(struct percpu_rw_semaphore *,
+                                const char *, struct lock_class_key *);
 extern void percpu_free_rwsem(struct percpu_rw_semaphore *);
 
+#define percpu_init_rwsem(brw)  \
+({                                                              \
+        static struct lock_class_key rwsem_key;                 \
+        __percpu_init_rwsem(brw, #brw, &rwsem_key);             \
+})
+
 #endif
diff --git a/lib/percpu-rwsem.c b/lib/percpu-rwsem.c
index ce92ab563a08..652a8ee8efe9 100644
--- a/lib/percpu-rwsem.c
+++ b/lib/percpu-rwsem.c
@@ -2,18 +2,21 @@
 #include <linux/rwsem.h>
 #include <linux/percpu.h>
 #include <linux/wait.h>
+#include <linux/lockdep.h>
 #include <linux/percpu-rwsem.h>
 #include <linux/rcupdate.h>
 #include <linux/sched.h>
 #include <linux/errno.h>
 
-int percpu_init_rwsem(struct percpu_rw_semaphore *brw)
+int __percpu_init_rwsem(struct percpu_rw_semaphore *brw,
+                        const char *name, struct lock_class_key *rwsem_key)
 {
         brw->fast_read_ctr = alloc_percpu(int);
         if (unlikely(!brw->fast_read_ctr))
                 return -ENOMEM;
 
-        init_rwsem(&brw->rw_sem);
+        /* ->rw_sem represents the whole percpu_rw_semaphore for lockdep */
+        __init_rwsem(&brw->rw_sem, name, rwsem_key);
         atomic_set(&brw->write_ctr, 0);
         atomic_set(&brw->slow_read_ctr, 0);
         init_waitqueue_head(&brw->write_waitq);
@@ -66,19 +69,29 @@ static bool update_fast_ctr(struct percpu_rw_semaphore *brw, unsigned int val)
 /*
  * Like the normal down_read() this is not recursive, the writer can
  * come after the first percpu_down_read() and create the deadlock.
+ *
+ * Note: returns with lock_is_held(brw->rw_sem) == T for lockdep,
+ * percpu_up_read() does rwsem_release(). This pairs with the usage
+ * of ->rw_sem in percpu_down/up_write().
  */
 void percpu_down_read(struct percpu_rw_semaphore *brw)
 {
-        if (likely(update_fast_ctr(brw, +1)))
+        might_sleep();
+        if (likely(update_fast_ctr(brw, +1))) {
+                rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 0, _RET_IP_);
                 return;
+        }
 
         down_read(&brw->rw_sem);
         atomic_inc(&brw->slow_read_ctr);
-        up_read(&brw->rw_sem);
+        /* avoid up_read()->rwsem_release() */
+        __up_read(&brw->rw_sem);
 }
 
 void percpu_up_read(struct percpu_rw_semaphore *brw)
 {
+        rwsem_release(&brw->rw_sem.dep_map, 1, _RET_IP_);
+
         if (likely(update_fast_ctr(brw, -1)))
                 return;