10:24 a.m.
$ virt-sparsify input output
[ 0.0] Create overlay file in /tmp to protect source disk
[ 0.0] Examine source disk
^C
guestfs_close: g->lock: Device or resource busy
Aborted (core dumped)
The reason for this is because virt-sparsify calls exit(2) in the
SIGINT signal handler, which causes the close_handles atexit handler
to run, which calls guestfs_close. However the same handle is in the
middle of a guestfs_* call, and the code in lib/handle.c catches this
case and calls abort(2).
(The same situation could happen from threaded code.)
The solution is to ignore the case where guestfs_close is called from
close_handles and the lock is held (the handle will be left open in
this case, but the recovery process should reap qemu).
Fixes commit b9847b404cdb57b362f486b5ccbedafa7ad38fa6.
---
lib/handle.c | 75 +++++++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 51 insertions(+), 24 deletions(-)
diff --git a/lib/handle.c b/lib/handle.c
index 449ab42a6..19caad813 100644
--- a/lib/handle.c
+++ b/lib/handle.c
@@ -43,6 +43,7 @@
static int shutdown_backend (guestfs_h *g, int check_for_errors);
static void close_handles (void);
+static void do_close (guestfs_h *g, int ignore_recursive);
gl_lock_define_initialized (static, handles_lock);
static guestfs_h *handles = NULL;
@@ -323,15 +324,7 @@ guestfs_impl_parse_environment_list (guestfs_h *g, char * const
*strings)
void
guestfs_close (guestfs_h *g)
{
- struct hv_param *hp, *hp_next;
guestfs_h **gg;
- int r;
-
- if (g->state == NO_HANDLE) {
- /* Not safe to call ANY callbacks here, so ... */
- fprintf (stderr, _("guestfs_close: called twice on the same handle\n"));
- return;
- }
/* Remove the handle from the handles list. */
if (g->close_on_exit) {
@@ -342,6 +335,45 @@ guestfs_close (guestfs_h *g)
gl_lock_unlock (handles_lock);
}
+ do_close (g, 0);
+}
+
+static void
+do_close (guestfs_h *g, int ignore_recursive)
+{
+ struct hv_param *hp, *hp_next;
+ int r;
+
+ if (g->state == NO_HANDLE) {
+ /* Not safe to call ANY callbacks here, so ... */
+ fprintf (stderr, _("guestfs_close: called twice on the same handle\n"));
+ return;
+ }
+
+ /* Destroy the handle lock first so we can detect the case where
+ * guestfs_close is called during another guestfs_* call on the same
+ * handle. This can happen if exit(3) is called from a signal
+ * handler or another thread during a guestfs_* call, which will
+ * cause the close_handles atexit handler to run, calling us here
+ * with ignore_recursive == 1.
+ */
+ r = glthread_recursive_lock_destroy (&g->lock);
+ if (r != 0) {
+ if (r == EBUSY && ignore_recursive)
+ return;
+
+ /* If pthread_mutex_destroy returns 16 (EBUSY), this indicates
+ * that the lock is held somewhere. That means a programming
+ * error if the main program is using threads.
+ */
+ errno = r;
+ perror ("guestfs_close: g->lock");
+ /* While we're debugging locks in libguestfs I want this to fail
+ * noisily.
+ */
+ abort ();
+ }
+
if (g->trace) {
const char trace_msg[] = "close";
@@ -403,21 +435,6 @@ guestfs_close (guestfs_h *g)
free (g->append);
guestfs_int_free_error_data_list (g);
gl_tls_key_destroy (g->error_data);
- r = glthread_recursive_lock_destroy (&g->lock);
- if (r != 0) {
- /* If pthread_mutex_destroy returns 16 (EBUSY), this indicates
- * that the lock is held somewhere. That means a programming
- * error if the main program is using threads.
- */
- errno = r;
- perror ("guestfs_close: g->lock");
- /* While we're debugging locks in libguestfs I want this to fail
- * noisily. Remove this later since there are valid times when
- * this might fail such as if the program exits during a
- * libguestfs operation.
- */
- abort ();
- }
free (g);
}
@@ -492,7 +509,17 @@ shutdown_backend (guestfs_h *g, int check_for_errors)
static void
close_handles (void)
{
- while (handles) guestfs_close (handles);
+ guestfs_h *g, *g_next;
+
+ gl_lock_lock (handles_lock);
+ g = handles;
+ handles = NULL;
+ while (g) {
+ g_next = g->next;
+ do_close (g, 1);
+ g = g_next;
+ }
+ gl_lock_unlock (handles_lock);
}
int
--
2.13.2