Update copyright dates with scripts/update-copyrights.

[thirdparty/glibc.git] / nptl / pthread_rwlock_unlock.c

diff --git a/nptl/pthread_rwlock_unlock.c b/nptl/pthread_rwlock_unlock.c
index a727d89b9cf89854ab0b3d6a35c23e45cda54791..320837d5afdd3ee86bdf6dbde8f3205a5ee9f2fb 100644 (file)
--- a/nptl/pthread_rwlock_unlock.c
+++ b/nptl/pthread_rwlock_unlock.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2003-2012 Free Software Foundation, Inc.
+/* Copyright (C) 2003-2017 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
 
@@ -19,37 +19,55 @@
 #include <errno.h>
 #include <sysdep.h>
 #include <lowlevellock.h>
+#include <futex-internal.h>
 #include <pthread.h>
 #include <pthreadP.h>
 #include <stap-probe.h>
+#include <elide.h>
+
 
 /* Unlock RWLOCK.  */
 int
 __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
 {
+  int futex_shared =
+      rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED;
+
   LIBC_PROBE (rwlock_unlock, 1, rwlock);
 
+  /* Trying to elide an unlocked lock may crash the process.  This
+     is expected and is compatible with POSIX.1-2008: "results are
+     undefined if the read-write lock rwlock is not held by the
+     calling thread".  */
+  if (ELIDE_UNLOCK (rwlock->__data.__writer == 0
+                   && rwlock->__data.__nr_readers == 0))
+    return 0;
+
   lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
   if (rwlock->__data.__writer)
     rwlock->__data.__writer = 0;
   else
     --rwlock->__data.__nr_readers;
+  /* If there are still readers present, we do not yet need to wake writers
+     nor are responsible to wake any readers.  */
   if (rwlock->__data.__nr_readers == 0)
     {
+      /* Note that if there is a blocked writer, we effectively make it
+        responsible for waking any readers because we don't wake readers in
+        this case.  */
       if (rwlock->__data.__nr_writers_queued)
        {
          ++rwlock->__data.__writer_wakeup;
          lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
-         lll_futex_wake (&rwlock->__data.__writer_wakeup, 1,
-                         rwlock->__data.__shared);
+         futex_wake (&rwlock->__data.__writer_wakeup, 1, futex_shared);
          return 0;
        }
       else if (rwlock->__data.__nr_readers_queued)
        {
          ++rwlock->__data.__readers_wakeup;
          lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
-         lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
-                         rwlock->__data.__shared);
+         futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
+                     futex_shared);
          return 0;
        }
     }
@@ -58,4 +76,4 @@ __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
 }
 
 weak_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock)
-strong_alias (__pthread_rwlock_unlock, __pthread_rwlock_unlock_internal)
+hidden_def (__pthread_rwlock_unlock)