Cleanup: Re-organise source dir

[userspace-rcu.git] / src / compat_futex.c

diff --git a/src/compat_futex.c b/src/compat_futex.c
new file mode 100644 (file)
index 0000000..9e918fe
--- /dev/null
+++ b/src/compat_futex.c
@@ -0,0 +1,154 @@
+/*
+ * compat_futex.c
+ *
+ * Userspace RCU library - sys_futex compatibility code
+ *
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdio.h>
+#include <pthread.h>
+#include <signal.h>
+#include <assert.h>
+#include <errno.h>
+#include <poll.h>
+#include <stdint.h>
+
+#include <urcu/arch.h>
+#include <urcu/futex.h>
+#include <urcu/system.h>
+
+/*
+ * Using attribute "weak" for __urcu_compat_futex_lock and
+ * __urcu_compat_futex_cond. Those are globally visible by the entire
+ * program, even though many shared objects may have their own version.
+ * The first version that gets loaded will be used by the entire program
+ * (executable and all shared objects).
+ */
+
+__attribute__((weak))
+pthread_mutex_t __urcu_compat_futex_lock = PTHREAD_MUTEX_INITIALIZER;
+__attribute__((weak))
+pthread_cond_t __urcu_compat_futex_cond = PTHREAD_COND_INITIALIZER;
+
+/*
+ * _NOT SIGNAL-SAFE_. pthread_cond is not signal-safe anyway. Though.
+ * For now, timeout, uaddr2 and val3 are unused.
+ * Waiter will relinquish the CPU until woken up.
+ */
+
+int compat_futex_noasync(int32_t *uaddr, int op, int32_t val,
+       const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
+{
+       int ret = 0, lockret;
+
+       /*
+        * Check if NULL. Don't let users expect that they are taken into
+        * account.
+        */
+       assert(!timeout);
+       assert(!uaddr2);
+       assert(!val3);
+
+       /*
+        * memory barriers to serialize with the previous uaddr modification.
+        */
+       cmm_smp_mb();
+
+       lockret = pthread_mutex_lock(&__urcu_compat_futex_lock);
+       if (lockret) {
+               errno = lockret;
+               ret = -1;
+               goto end;
+       }
+       switch (op) {
+       case FUTEX_WAIT:
+               /*
+                * Wait until *uaddr is changed to something else than "val".
+                * Comparing *uaddr content against val figures out which
+                * thread has been awakened.
+                */
+               while (CMM_LOAD_SHARED(*uaddr) == val)
+                       pthread_cond_wait(&__urcu_compat_futex_cond,
+                               &__urcu_compat_futex_lock);
+               break;
+       case FUTEX_WAKE:
+               /*
+                * Each wake is sending a broadcast, thus attempting wakeup of
+                * all awaiting threads, independently of their respective
+                * uaddr.
+                */
+               pthread_cond_broadcast(&__urcu_compat_futex_cond);
+               break;
+       default:
+               errno = EINVAL;
+               ret = -1;
+       }
+       lockret = pthread_mutex_unlock(&__urcu_compat_futex_lock);
+       if (lockret) {
+               errno = lockret;
+               ret = -1;
+       }
+end:
+       return ret;
+}
+
+/*
+ * _ASYNC SIGNAL-SAFE_.
+ * For now, timeout, uaddr2 and val3 are unused.
+ * Waiter will busy-loop trying to read the condition.
+ * It is OK to use compat_futex_async() on a futex address on which
+ * futex() WAKE operations are also performed.
+ */
+
+int compat_futex_async(int32_t *uaddr, int op, int32_t val,
+       const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
+{
+       int ret = 0;
+
+       /*
+        * Check if NULL. Don't let users expect that they are taken into
+        * account.
+        */
+       assert(!timeout);
+       assert(!uaddr2);
+       assert(!val3);
+
+       /*
+        * Ensure previous memory operations on uaddr have completed.
+        */
+       cmm_smp_mb();
+
+       switch (op) {
+       case FUTEX_WAIT:
+               while (CMM_LOAD_SHARED(*uaddr) == val) {
+                       if (poll(NULL, 0, 10) < 0) {
+                               ret = -1;
+                               /* Keep poll errno. Caller handles EINTR. */
+                               goto end;
+                       }
+               }
+               break;
+       case FUTEX_WAKE:
+               break;
+       default:
+               errno = EINVAL;
+               ret = -1;
+       }
+end:
+       return ret;
+}