/*
* Process describes processes we create.
* It contains a semaphore that can be waited on in order to wait
- * for process termination. It's accessed in our SIGCHLD handler,
- * when status is updated (and pid cleared, to not clash with
- * subsequent processes that may get executed).
+ * for process termination.
*/
typedef struct _Process {
pid_t pid; /* the pid of the process. This value is only valid until the process has exited. */
* the process has exited, so that the information there isn't lost.
*/
gpointer handle;
- gboolean freeable;
gboolean signalled;
struct _Process *next;
} Process;
static gchar *cli_launcher;
-/* The signal-safe logic to use processes goes like this:
- * - The list must be safe to traverse for the signal handler at all times.
- * It's safe to: prepend an entry (which is a single store to 'processes'),
- * unlink an entry (assuming the unlinked entry isn't freed and doesn't
- * change its 'next' pointer so that it can still be traversed).
- * When cleaning up we first unlink an entry, then we verify that
- * the read lock isn't locked. Then we can free the entry, since
- * we know that nobody is using the old version of the list (including
- * the unlinked entry).
- * We also need to lock when adding and cleaning up so that those two
- * operations don't mess with eachother. (This lock is not used in the
- * signal handler) */
static Process *processes;
static mono_mutex_t processes_mutex;
static gint32 cleaning_up;
Process *process;
Process *prev = NULL;
- GSList *finished = NULL;
- GSList *l;
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_IO_LAYER, "%s", __func__);
if (InterlockedCompareExchange (&cleaning_up, 1, 0) != 0)
return;
+ /*
+ * This needs to be done outside the lock but atomically, hence the CAS above.
+ */
for (process = processes; process; process = process->next) {
if (process->signalled && process->handle) {
/* This process has exited and we need to remove the artifical ref
}
}
- /*
- * Remove processes which exited from the processes list.
- * We need to synchronize with the sigchld handler here, which runs
- * asynchronously. The handler requires that the processes list
- * remain valid.
- */
mono_os_mutex_lock (&processes_mutex);
- for (process = processes; process; process = process->next) {
- if (process->handle_count == 0 && process->freeable) {
+ for (process = processes; process;) {
+ Process *next = process->next;
+ if (process->handle_count == 0 && process->signalled) {
/*
* Unlink the entry.
- * This code can run parallel with the sigchld handler, but the
- * modifications it makes are safe.
*/
if (process == processes)
processes = process->next;
else
prev->next = process->next;
- finished = g_slist_prepend (finished, process);
+
+ mono_os_sem_destroy (&process->exit_sem);
+ g_free (process);
} else {
prev = process;
}
+ process = next;
}
- mono_memory_barrier ();
-
- for (l = finished; l; l = l->next) {
- /*
- * All the entries in the finished list are unlinked from processes, and
- * they have the 'finished' flag set, which means the sigchld handler is done
- * accessing them.
- */
- process = (Process *)l->data;
- mono_os_sem_destroy (&process->exit_sem);
- g_free (process);
- }
- g_slist_free (finished);
-
mono_os_mutex_unlock (&processes_mutex);
mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_IO_LAYER, "%s done", __func__);
#if HAVE_SIGACTION
MONO_SIGNAL_HANDLER_FUNC (static, mono_sigchld_signal_handler, (int _dummy, siginfo_t *info, void *context))
+{
+ /*
+ * Don't want to do any complicated processing here so just wake up the finalizer thread which will call
+ * mono_w32process_signal_finished ().
+ */
+ int old_errno = errno;
+
+ mono_gc_finalize_notify ();
+
+ errno = old_errno;
+}
+
+static void
+process_add_sigchld_handler (void)
+{
+ struct sigaction sa;
+
+ sa.sa_sigaction = mono_sigchld_signal_handler;
+ sigemptyset (&sa.sa_mask);
+ sa.sa_flags = SA_NOCLDSTOP | SA_SIGINFO | SA_RESTART;
+ g_assert (sigaction (SIGCHLD, &sa, NULL) != -1);
+ mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_IO_LAYER, "Added SIGCHLD handler");
+}
+
+#endif
+
+/*
+ * mono_w32process_signal_finished:
+ *
+ * Signal the exit semaphore for processes which have finished.
+ */
+void
+mono_w32process_signal_finished (void)
{
int status;
int pid;
if (pid <= 0)
break;
- /*
- * This can run concurrently with the code in the rest of this module.
- */
+ mono_os_mutex_lock (&processes_mutex);
+
for (process = processes; process; process = process->next) {
if (process->pid != pid)
continue;
process->signalled = TRUE;
process->status = status;
mono_os_sem_post (&process->exit_sem);
- mono_memory_barrier ();
- /* Mark this as freeable, the pointer becomes invalid afterwards */
- process->freeable = TRUE;
break;
}
- } while (1);
-}
-static void
-process_add_sigchld_handler (void)
-{
- struct sigaction sa;
-
- sa.sa_sigaction = mono_sigchld_signal_handler;
- sigemptyset (&sa.sa_mask);
- sa.sa_flags = SA_NOCLDSTOP | SA_SIGINFO;
- g_assert (sigaction (SIGCHLD, &sa, NULL) != -1);
- mono_trace (G_LOG_LEVEL_DEBUG, MONO_TRACE_IO_LAYER, "Added SIGCHLD handler");
+ mono_os_mutex_unlock (&processes_mutex);
+ } while (1);
}
-#endif
-
static gboolean
is_readable_or_executable (const char *prog)
{
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