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Merge waitpid() from g_spawn_sync into gmain()
This is preparatory work for a future commit which will add a "catchall" waitpid API. If we don't synchronize here with the worker thread, race conditions are possible. This also ensures we have an error message if someone adds a child watch for a nonexistent pid, etc. Previously, we'd simply keep calling waitpid() getting ECHILD, and ignoring it until the source was removed. Now, we g_warning() and fire the source. Thirdly, this ensures that the waitpid() call in gmain handles EINTR, like the g_spawn_sync() one did. https://bugzilla.gnome.org/show_bug.cgi?id=687061
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0bdf7fecaf
commit
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20
glib/gmain.c
20
glib/gmain.c
@ -4421,12 +4421,24 @@ dispatch_unix_signals (void)
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if (!source->child_exited)
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{
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if (waitpid (source->pid, &source->child_status, WNOHANG) > 0)
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pid_t pid;
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do
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{
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source->child_exited = TRUE;
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wake_source ((GSource *) source);
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pid = waitpid (source->pid, &source->child_status, WNOHANG);
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if (pid > 0)
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{
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source->child_exited = TRUE;
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wake_source ((GSource *) source);
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}
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else if (pid == -1 && errno == ECHILD)
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{
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g_warning ("GChildWatchSource: Exit status of a child process was requested but ECHILD was received by waitpid(). Most likely the process is ignoring SIGCHLD, or some other thread is invoking waitpid() with a nonpositive first argument; either behavior can break applications that use g_child_watch_add()/g_spawn_sync() either directly or indirectly.");
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source->child_exited = TRUE;
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source->child_status = 0;
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wake_source ((GSource *) source);
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}
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}
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while (pid == -1 && errno == EINTR);
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}
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}
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}
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@ -46,6 +46,7 @@
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#include "genviron.h"
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#include "gmem.h"
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#include "gmain.h"
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#include "gshell.h"
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#include "gstring.h"
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#include "gstrfuncs.h"
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@ -212,6 +213,21 @@ read_data (GString *str,
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}
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}
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typedef struct {
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GMainLoop *loop;
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gint *status_p;
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} SyncWaitpidData;
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static void
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on_sync_waitpid (GPid pid,
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gint status,
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gpointer user_data)
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{
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SyncWaitpidData *data = user_data;
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*(data->status_p) = status;
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g_main_loop_quit (data->loop);
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}
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/**
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* g_spawn_sync:
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* @working_directory: (allow-none): child's current working directory, or %NULL to inherit parent's
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@ -267,6 +283,7 @@ g_spawn_sync (const gchar *working_directory,
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GString *errstr = NULL;
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gboolean failed;
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gint status;
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SyncWaitpidData waitpid_data;
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g_return_val_if_fail (argv != NULL, FALSE);
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g_return_val_if_fail (!(flags & G_SPAWN_DO_NOT_REAP_CHILD), FALSE);
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@ -399,45 +416,32 @@ g_spawn_sync (const gchar *working_directory,
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close_and_invalidate (&outpipe);
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if (errpipe >= 0)
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close_and_invalidate (&errpipe);
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/* Wait for child to exit, even if we have
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* an error pending.
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/* Now create a temporary main context and loop, with just one
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* waitpid source. We used to invoke waitpid() directly here, but
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* this way we unify with the worker thread in gmain.c.
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*/
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again:
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ret = waitpid (pid, &status, 0);
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{
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GMainContext *context;
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GMainLoop *loop;
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GSource *source;
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if (ret < 0)
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{
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if (errno == EINTR)
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goto again;
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else if (errno == ECHILD)
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{
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if (exit_status)
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{
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g_warning ("In call to g_spawn_sync(), exit status of a child process was requested but ECHILD was received by waitpid(). Most likely the process is ignoring SIGCHLD, or some other thread is invoking waitpid() with a nonpositive first argument; either behavior can break applications that use g_spawn_sync either directly or indirectly.");
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}
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else
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{
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/* We don't need the exit status. */
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}
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}
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else
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{
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if (!failed) /* avoid error pileups */
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{
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int errsv = errno;
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context = g_main_context_new ();
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loop = g_main_loop_new (context, TRUE);
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failed = TRUE;
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g_set_error (error,
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G_SPAWN_ERROR,
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G_SPAWN_ERROR_READ,
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_("Unexpected error in waitpid() (%s)"),
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g_strerror (errsv));
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}
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}
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}
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waitpid_data.loop = loop;
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waitpid_data.status_p = &status;
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source = g_child_watch_source_new (pid);
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g_source_set_callback (source, (GSourceFunc)on_sync_waitpid, &waitpid_data, NULL);
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g_source_attach (source, context);
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g_source_unref (source);
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g_main_loop_run (loop);
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g_main_context_unref (context);
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g_main_loop_unref (loop);
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}
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if (failed)
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{
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