On the revprop-cache branch: Since APR proc mutexes are only valid
within a process tree, we need our own global mutex mechanism.
It uses a lock file for global sync. and a svn_mutex__t for thread sync.
Also, fix an issue identified by testing without intrinsics.
* subversion/libsvn_subr/svn_named_atomic.c
(synched_read): must take a reference to the sync'ed data
(svn_named_atomic__read): adapt caller
(mutex_pool, mutex, lock_file): data for the new sync mechanism
(init_mutex, lock, unlock): implement new sync mechanism
git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/revprop-cache@1325463 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/subversion/libsvn_subr/svn_named_atomic.c b/subversion/libsvn_subr/svn_named_atomic.c
index 63da4ae..255c2b0 100644
--- a/subversion/libsvn_subr/svn_named_atomic.c
+++ b/subversion/libsvn_subr/svn_named_atomic.c
@@ -28,6 +28,7 @@
#include "svn_private_config.h"
#include "private/svn_atomic.h"
+#include "private/svn_mutex.h"
#include "svn_pools.h"
#include "svn_dirent_uri.h"
#include "svn_io.h"
@@ -99,7 +100,7 @@
/* Interlocked API / intrinsics guarantee full data synchronization
*/
-#define synched_read(value) value
+#define synched_read(mem) *mem
#define synched_write(mem, value) InterlockedExchange64(mem, value)
#define synched_add(mem, delta) InterlockedAdd64(mem, delta)
#define synched_cmpxchg(mem, value, comperand) \
@@ -111,7 +112,7 @@
/* GCC provides atomic intrinsics for most common CPU types
*/
-#define synched_read(value) value
+#define synched_read(mem) *mem
#define synched_write(mem, value) __sync_lock_test_and_set(mem, value)
#define synched_add(mem, delta) __sync_add_and_fetch(mem, delta)
#define synched_cmpxchg(mem, value, comperand) \
@@ -124,9 +125,9 @@
/* Default implementation
*/
static apr_int64_t
-synched_read(apr_int64_t value)
+synched_read(volatile apr_int64_t *mem)
{
- return value;
+ return *mem;
}
static apr_int64_t
@@ -216,9 +217,12 @@
*/
static struct svn_atomic_namespace__t default_namespace = {FALSE, NULL};
-/* Named global mutex to control access to the shared memory structures.
+/* Process sync. is handled by a lock file. Local thread sync. is done
+ * by an svn_mutex__t. They will all be initialized in init_mutex.
*/
-static apr_global_mutex_t *mutex = NULL;
+static apr_pool_t *mutex_pool = NULL;
+static svn_mutex__t *mutex = NULL;
+static apr_file_t *lock_file = NULL;
/* Initialization flag for the above used by svn_atomic__init_once.
*/
@@ -229,14 +233,20 @@
static svn_error_t *
init_mutex(void *baton, apr_pool_t *_pool)
{
- apr_pool_t *pool = svn_pool_create(NULL);
- apr_status_t apr_err = apr_global_mutex_create(&mutex,
- MUTEX_NAME,
- APR_LOCK_DEFAULT,
- pool);
- return apr_err
- ? svn_error_wrap_apr(apr_err, _("Can't create mutex for named atomics"))
- : SVN_NO_ERROR;
+ const char *temp_dir, *fname;
+
+ if (mutex_pool == NULL)
+ mutex_pool = svn_pool_create(NULL);
+ if (mutex == NULL)
+ SVN_ERR(svn_mutex__init(&mutex, TRUE, mutex_pool));
+
+ SVN_ERR(svn_io_temp_dir(&temp_dir, mutex_pool));
+ fname = svn_dirent_join(temp_dir, MUTEX_NAME, mutex_pool);
+
+ return svn_io_file_open(&lock_file, fname,
+ APR_READ | APR_WRITE | APR_CREATE,
+ APR_OS_DEFAULT,
+ mutex_pool);
}
/* Utility that acquires our global mutex and converts error types.
@@ -244,12 +254,15 @@
static svn_error_t *
lock(void)
{
- apr_status_t apr_err = apr_global_mutex_lock(mutex);
- if (apr_err)
- return svn_error_wrap_apr(apr_err,
- _("Can't lock mutex for named atomics"));
+ svn_error_t *err;
+
+ /* Get lock on the filehandle. */
+ SVN_ERR(svn_mutex__lock(mutex));
+ err = svn_io_lock_open_file(lock_file, TRUE, FALSE, mutex_pool);
- return SVN_NO_ERROR;
+ return err
+ ? svn_mutex__unlock(mutex, err)
+ : err;
}
/* Utility that releases the lock previously acquired via lock(). If the
@@ -259,12 +272,8 @@
static svn_error_t *
unlock(svn_error_t * outer_err)
{
- apr_status_t apr_err = apr_global_mutex_unlock(mutex);
- if (apr_err && !outer_err)
- return svn_error_wrap_apr(apr_err,
- _("Can't unlock mutex for named atomics"));
-
- return outer_err;
+ return svn_mutex__unlock(mutex,
+ svn_io_unlock_open_file(lock_file, mutex_pool));
}
/* Initialize the shared_mem_access_t given as BATON.
@@ -469,7 +478,7 @@
svn_named_atomic__t *atomic)
{
SVN_ERR(validate(atomic));
- SYNCHRONIZE(*value = synched_read(atomic->value));
+ SYNCHRONIZE(*value = synched_read(&atomic->value));
return SVN_NO_ERROR;
}
