Changeset 063a74b9 in mainline

Timestamp:

2013-09-07T22:17:45Z (11 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

7de18418

Parents:

a74d0ad

Message:

Futexes have the lock/unlock semantics and therefore need to use barriers.

File:

• uspace/lib/c/generic/futex.c (modified) (4 diffs)

uspace/lib/c/generic/futex.c

@@ -35 +35 @@
 #include <futex.h>
 #include <atomic.h>
+#include <libarch/barrier.h>
 #include <libc.h>
 #include <sys/types.h>
@@ -59 +60 @@
 int futex_trydown(futex_t *futex)
 {
-        return cas(futex, 1, 0);
+        int rc;
+
+        rc = cas(futex, 1, 0);
+        CS_ENTER_BARRIER();
+
+        return rc;
 }
 
@@ -73 +79 @@
 int futex_down(futex_t *futex)
 {
-        if ((atomic_signed_t) atomic_predec(futex) < 0)
+        atomic_signed_t nv;
+
+        nv = (atomic_signed_t) atomic_predec(futex);
+        CS_ENTER_BARRIER();
+        if (nv < 0)
                 return __SYSCALL1(SYS_FUTEX_SLEEP, (sysarg_t) &futex->count);
         
@@ -89 +99 @@
 int futex_up(futex_t *futex)
 {
+        CS_LEAVE_BARRIER();
+
         if ((atomic_signed_t) atomic_postinc(futex) < 0)
                 return __SYSCALL1(SYS_FUTEX_WAKEUP, (sysarg_t) &futex->count);