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Merge waitpid() from g_spawn_sync into gmain()

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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
This commit is contained in:
Colin Walters 2012-10-29 15:44:16 -04:00
parent 0bdf7fecaf
commit ce0022933c
2 changed files with 56 additions and 40 deletions
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20
glib/gmain.c
View File

@ -4421,12 +4421,24 @@ dispatch_unix_signals (void)
if (!source->child_exited)
{
if (waitpid (source->pid, &source->child_status, WNOHANG) > 0)
pid_t pid;
do
{
source->child_exited = TRUE;
wake_source ((GSource *) source);
pid = waitpid (source->pid, &source->child_status, WNOHANG);
if (pid > 0)
{
source->child_exited = TRUE;
wake_source ((GSource *) source);
}
else if (pid == -1 && errno == ECHILD)
{
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.");
source->child_exited = TRUE;
source->child_status = 0;
wake_source ((GSource *) source);
}
}
while (pid == -1 && errno == EINTR);
}
}
}

76
glib/gspawn.c
View File

@ -46,6 +46,7 @@
#include "genviron.h"
#include "gmem.h"
#include "gmain.h"
#include "gshell.h"
#include "gstring.h"
#include "gstrfuncs.h"
@ -212,6 +213,21 @@ read_data (GString *str,
}
}
typedef struct {
GMainLoop *loop;
gint *status_p;
} SyncWaitpidData;
static void
on_sync_waitpid (GPid pid,
gint status,
gpointer user_data)
{
SyncWaitpidData *data = user_data;
*(data->status_p) = status;
g_main_loop_quit (data->loop);
}
/**
* g_spawn_sync:
* @working_directory: (allow-none): child's current working directory, or %NULL to inherit parent's
@ -267,6 +283,7 @@ g_spawn_sync (const gchar *working_directory,
GString *errstr = NULL;
gboolean failed;
gint status;
SyncWaitpidData waitpid_data;
g_return_val_if_fail (argv != NULL, FALSE);
g_return_val_if_fail (!(flags & G_SPAWN_DO_NOT_REAP_CHILD), FALSE);
@ -399,45 +416,32 @@ g_spawn_sync (const gchar *working_directory,
close_and_invalidate (&outpipe);
if (errpipe >= 0)
close_and_invalidate (&errpipe);
/* Wait for child to exit, even if we have
* an error pending.
/* Now create a temporary main context and loop, with just one
* waitpid source. We used to invoke waitpid() directly here, but
* this way we unify with the worker thread in gmain.c.
*/
again:
ret = waitpid (pid, &status, 0);
{
GMainContext *context;
GMainLoop *loop;
GSource *source;
if (ret < 0)
{
if (errno == EINTR)
goto again;
else if (errno == ECHILD)
{
if (exit_status)
{
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.");
}
else
{
/* We don't need the exit status. */
}
}
else
{
if (!failed) /* avoid error pileups */
{
int errsv = errno;
context = g_main_context_new ();
loop = g_main_loop_new (context, TRUE);
failed = TRUE;
g_set_error (error,
G_SPAWN_ERROR,
G_SPAWN_ERROR_READ,
_("Unexpected error in waitpid() (%s)"),
g_strerror (errsv));
}
}
}
waitpid_data.loop = loop;
waitpid_data.status_p = &status;
source = g_child_watch_source_new (pid);
g_source_set_callback (source, (GSourceFunc)on_sync_waitpid, &waitpid_data, NULL);
g_source_attach (source, context);
g_source_unref (source);
g_main_loop_run (loop);
g_main_context_unref (context);
g_main_loop_unref (loop);
}
if (failed)
{