1 files changed, 61 insertions, 0 deletions
diff --git a/sysdeps/mach/hurd/pt-rwlock-rdlock.c b/sysdeps/mach/hurd/pt-rwlock-rdlock.c
new file mode 100644
index 0000000..0708bca
--- /dev/null
+++ b/sysdeps/mach/hurd/pt-rwlock-rdlock.c
@@ -0,0 +1,61 @@
+/* Copyright (C) 2016 Free Software Foundation, Inc.
+   Contributed by Agustina Arzille <avarzille@riseup.net>, 2016.
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License
+   as published by the Free Software Foundation; either
+   version 2 of the license, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+   GNU Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with this program; if not, see
+   <http://www.gnu.org/licenses/>.
+*/
+
+#include <pthread.h>
+#include <pt-internal.h>
+#include <bits/pt-atomic.h>
+#include <hurdlock.h>
+#include "pt-rwlock.h"
+
+int __pthread_rwlock_rdlock (pthread_rwlock_t *rwp)
+{
+  int flags = rwp->__flags & GSYNC_SHARED;
+
+  /* Test that we don't own the write-lock already. */
+  if (rwl_owned_p (rwp, early_pthread_self(), flags))
+    return (EDEADLK);
+
+  while (1)
+    {
+      union __hurd_xint tmp = { atomic_loadx (&rwp->__oid_nrd.__qv) };
+      if ((rwl_oid (tmp) & ID_MASK) == 0)
+        {
+          /* The lock is either unowned, or the readers hold it. */
+          if (catomic_casx_bool (&rwp->__oid_nrd.__qv,
+              hurd_xint_pair (tmp.__lo, tmp.__hi),
+              hurd_xint_pair (RWLOCK_RO, rwl_nrd (tmp) + 1)))
+            {
+              /* If we grabbed an unowned lock and there were readers
+               * queued, notify our fellows so they stop blocking. */
+              if (rwl_oid (tmp) != RWLOCK_RO && rwl_nrd (tmp) > 0)
+                lll_wake (&rwl_oid(rwp->__oid_nrd), flags | GSYNC_BROADCAST);
+
+              return (0);
+            }
+        }
+      else
+        {
+          /* A writer holds the lock. Sleep. */
+          atomic_increment (&rwl_nrd(rwp->__oid_nrd));
+          lll_wait (&rwl_oid(rwp->__oid_nrd), rwl_oid (tmp), flags);
+          atomic_decrement (&rwl_nrd(rwp->__oid_nrd));
+        }
+    }
+}
+
+strong_alias (__pthread_rwlock_rdlock, pthread_rwlock_rdlock)