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registrybackend: make subscribe and unsubscribe thread-safe

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The registry backend uses a thread to monitor
registry changes and send notifications.
The state of this thread and structures used
for communicating with it are kept in the watch
variable.
The subscribe and unsubscribe functions might be
concurrently called from multiple threads and
need to communicate with the monitoring thread.
For this reason we need to synchronize the access
to the watch variable.
This commit is contained in:
Silvio Lazzeretti 2025-01-30 17:34:30 +01:00 committed by Ignacio Casal Quinteiro
parent 9c7a57dcc5
commit f45b5ea776
1 changed files with 25 additions and 2 deletions
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27
gio/gregistrysettingsbackend.c
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@ -179,6 +179,10 @@ typedef struct {
CRITICAL_SECTION *cache_lock;
GNode *cache_root;
/* A lock to protect access to the watch variable */
CRITICAL_SECTION watch_lock;
/* Contains the state of the watching thread. Any access to this variable
* must be done while holding the watch_lock critical section. */
WatchThreadState *watch;
} GRegistrySettingsBackend;
@ -1901,6 +1905,7 @@ watch_thread_function (LPVOID parameter)
return -1;
}
/* This function assumes you hold the watch lock! */
static gboolean
watch_start (GRegistrySettingsBackend *self)
{
@ -1947,6 +1952,7 @@ fail:
return FALSE;
}
/* This function assumes you hold the watch lock! */
/* This function assumes you hold the message lock! */
static void
watch_stop_unlocked (GRegistrySettingsBackend *self)
@ -1982,6 +1988,7 @@ watch_stop_unlocked (GRegistrySettingsBackend *self)
self->watch = NULL;
}
/* This function assumes you hold the watch lock! */
static gboolean
watch_add_notify (GRegistrySettingsBackend *self,
HANDLE event,
@ -2055,6 +2062,7 @@ watch_add_notify (GRegistrySettingsBackend *self,
return TRUE;
}
/* This function assumes you hold the watch lock! */
static void
watch_remove_notify (GRegistrySettingsBackend *self,
const gchar *key_name)
@ -2105,12 +2113,17 @@ g_registry_settings_backend_subscribe (GSettingsBackend *backend,
HANDLE event;
LONG result;
EnterCriticalSection (&self->watch_lock);
if (self->watch == NULL && !watch_start (self))
return;
{
LeaveCriticalSection (&self->watch_lock);
return;
}
if (g_atomic_int_dec_and_test (&self->watch->watches_remaining))
{
g_atomic_int_inc (&self->watch->watches_remaining);
LeaveCriticalSection (&self->watch_lock);
g_warning ("subscribe() failed: only %i different paths may be watched.", MAX_WATCHES);
return;
}
@ -2139,6 +2152,7 @@ g_registry_settings_backend_subscribe (GSettingsBackend *backend,
{
g_message_win32_error (result, "gregistrysettingsbackend: Unable to subscribe to key %s.", key_name);
g_atomic_int_inc (&self->watch->watches_remaining);
LeaveCriticalSection (&self->watch_lock);
return;
}
@ -2147,6 +2161,7 @@ g_registry_settings_backend_subscribe (GSettingsBackend *backend,
{
g_message_win32_error (result, "gregistrysettingsbackend: CreateEvent failed.");
g_atomic_int_inc (&self->watch->watches_remaining);
LeaveCriticalSection (&self->watch_lock);
RegCloseKey (hpath);
return;
}
@ -2159,15 +2174,21 @@ g_registry_settings_backend_subscribe (GSettingsBackend *backend,
RegCloseKey (hpath);
CloseHandle (event);
}
LeaveCriticalSection (&self->watch_lock);
}
static void
g_registry_settings_backend_unsubscribe (GSettingsBackend *backend,
const char *key_name)
{
GRegistrySettingsBackend *self = G_REGISTRY_SETTINGS_BACKEND (backend);
trace ("unsubscribe: %s.\n", key_name);
watch_remove_notify (G_REGISTRY_SETTINGS_BACKEND (backend), key_name);
EnterCriticalSection (&self->watch_lock);
watch_remove_notify (self, key_name);
LeaveCriticalSection (&self->watch_lock);
}
/********************************************************************************
@ -2191,6 +2212,7 @@ g_registry_settings_backend_finalize (GObject *object)
EnterCriticalSection (self->watch->message_lock);
watch_stop_unlocked (self);
}
DeleteCriticalSection (&self->watch_lock);
DeleteCriticalSection (self->cache_lock);
g_slice_free (CRITICAL_SECTION, self->cache_lock);
@ -2341,6 +2363,7 @@ g_registry_settings_backend_init (GRegistrySettingsBackend *self)
InitializeCriticalSection (self->cache_lock);
self->watch = NULL;
InitializeCriticalSection (&self->watch_lock);
}
/**