lib/fetcher-util: Wake up main context when a request is complete

Since the value of `data->done` is not watched by the main context, the
context doesn’t know to wake up from `g_main_context_iteration()` when
that value is changed. The code currently relies on something else
happening to wake the main context up shortly after `data->done` is set.

That doesn’t seem very reliable, so wake the main context up explicitly.

Spotted this while reading the code while trying to debug a stall with
backtrace:
```
5  0x00007ffff68bbbfb in g_main_context_iteration (context=0x60f000136900, may_block=1) at ../../source/glib/glib/gmain.c:4343
6  0x00007fffdc0e50db in _ostree_fetcher_mirrored_request_to_membuf_once (fetcher=0x604001138c10, mirrorlist=0x603001df18b0, filename=0x7fffdc1049e7 "summary.sig", flags=OSTREE_FETCHER_REQUEST_OPTIONAL_CONTENT, if_none_match=0x602002f3b7f0 "\"640a49ff-250\"", if_modified_since=1678395903, out_contents=0x7fffdadd0e80, out_not_modified=0x7fffdadd0e38, out_etag=0x7fffdadd0e28, out_last_modified=0x7fffdadd0e00, max_size=10485760, cancellable=0x6060004bd720, error=0x7fffdadd0ca0) at src/libostree/ostree-fetcher-util.c:95
7  0x00007fffdc0e52e0 in _ostree_fetcher_mirrored_request_to_membuf (fetcher=0x604001138c10, mirrorlist=0x603001df18b0, filename=0x7fffdc1049e7 "summary.sig", flags=OSTREE_FETCHER_REQUEST_OPTIONAL_CONTENT, if_none_match=0x602002f3b7f0 "\"640a49ff-250\"", if_modified_since=1678395903, n_network_retries=5, out_contents=0x7fffdadd0e80, out_not_modified=0x7fffdadd0e38, out_etag=0x7fffdadd0e28, out_last_modified=0x7fffdadd0e00, max_size=10485760, cancellable=0x6060004bd720, error=0x7fffdadd10c0) at src/libostree/ostree-fetcher-util.c:155
8  0x00007fffdc08d937 in _ostree_preload_metadata_file (self=0x61600057bd80, fetcher=0x604001138c10, mirrorlist=0x603001df18b0, filename=0x7fffdc1049e7 "summary.sig", is_metalink=0, if_none_match=0x602002f3b7f0 "\"640a49ff-250\"", if_modified_since=1678395903, n_network_retries=5, out_bytes=0x7fffdadd0e80, out_not_modified=0x7fffdadd0e38, out_etag=0x7fffdadd0e28, out_last_modified=0x7fffdadd0e00, cancellable=0x6060004bd720, error=0x7fffdadd10c0) at src/libostree/ostree-repo-pull.c:3329
9  0x00007fffdc099712 in ostree_repo_remote_fetch_summary_with_options (self=0x61600057bd80, name=0x6020007f4fd0 "eos-apps", options=0x0, out_summary=0x7fffdadd0f88, out_signatures=0x7fffdadd0f80, cancellable=0x6060004bd720, error=0x7fffdadd10c0) at src/libostree/ostree-repo-pull.c:6675
10 0x00007fffdc06887f in ostree_repo_remote_fetch_summary (self=0x61600057bd80, name=0x6020007f4fd0 "eos-apps", out_summary=0x7fffdadd0f88, out_signatures=0x7fffdadd0f80, cancellable=0x6060004bd720, error=0x7fffdadd10c0) at src/libostree/ostree-repo.c:2706
11 0x00007fffdc18f5de in flatpak_dir_remote_fetch_summary (self=0x60c00577e640, name_or_uri=0x6020007f4fd0 "eos-apps", only_cached=0, out_summary=0x7fffdadd10f0, out_summary_sig=0x7fffdadd10e8, cancellable=0x6060004bd720, error=0x7fffdadd10c0) at /opt/gnome/source/flatpak/common/flatpak-dir.c:12235
12 0x00007fffdc1918cb in _flatpak_dir_get_remote_state (self=0x60c00577e640, remote_or_uri=0x6020007f4fd0 "eos-apps", optional=1, local_only=0, only_cached=0, opt_summary_is_index=0, opt_summary=0x0, opt_summary_sig=0x0, cancellable=0x6060004bd720, error=0x7fffdadd15a0) at /opt/gnome/source/flatpak/common/flatpak-dir.c:12789
13 0x00007fffdc19206d in flatpak_dir_get_remote_state_optional (self=0x60c00577e640, remote=0x6020007f4fd0 "eos-apps", only_cached=0, cancellable=0x6060004bd720, error=0x7fffdadd15a0) at /opt/gnome/source/flatpak/common/flatpak-dir.c:12953
14 0x00007fffdc1784f2 in flatpak_dir_update_appstream (self=0x60c00577e640, remote=0x6020007f4fd0 "eos-apps", arch=0x7fffdc239f30 "x86_64", out_changed=0x0, progress=0x6110007479c0, cancellable=0x6060004bd720, error=0x7fffdadd15a0) at /opt/gnome/source/flatpak/common/flatpak-dir.c:5182
```

I don’t think it’ll fix it (calling `g_main_context_wakeup()` on the
context in the debugger didn’t help), but it can’t hurt.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

diff --git a/src/libostree/ostree-fetcher-util.c b/src/libostree/ostree-fetcher-util.c
index 1b317630faa66d2f39753d540ab02829410687cf..ecd6bc2314c38536ad61e604c0866baef3e625e4 100644 (file)
--- a/src/libostree/ostree-fetcher-util.c
+++ b/src/libostree/ostree-fetcher-util.c
@@ -37,6 +37,7 @@ typedef struct
   char            *result_etag;
   guint64          result_last_modified;  /* second since the epoch */
   gboolean         done;
+  GMainContext    *main_context;  /* (owned) */
   GError         **error;
 }
   FetchUriSyncData;
@@ -54,6 +55,7 @@ fetch_uri_sync_on_complete (GObject        *object,
                                                   &data->result_etag, &data->result_last_modified,
                                                   data->error);
   data->done = TRUE;
+  g_main_context_wakeup (data->main_context);
 }
 
 static gboolean
@@ -84,6 +86,7 @@ _ostree_fetcher_mirrored_request_to_membuf_once  (OstreeFetcher              *fe
   mainctx = g_main_context_new ();
   g_main_context_push_thread_default (mainctx);
 
+  data.main_context = g_main_context_ref (mainctx);
   data.done = FALSE;
   data.error = error;
 
@@ -127,6 +130,7 @@ _ostree_fetcher_mirrored_request_to_membuf_once  (OstreeFetcher              *fe
     g_main_context_pop_thread_default (mainctx);
   g_clear_pointer (&data.result_buf, g_bytes_unref);
   g_clear_pointer (&data.result_etag, g_free);
+  g_clear_pointer (&data.main_context, g_main_context_unref);
   return ret;
 }