Re: [Libguestfs] [PATCH 2/5] threads: Acquire and release the lock around each public guestfs_* API.
Hi,
On Saturday 06 June 2015 14:20:38 Richard W.M. Jones wrote:
Since each ACQUIRE_LOCK/RELEASE_LOCK call must balance, this code is
difficult to debug. Enable DEBUG_LOCK to add some prints which can
help.
There's some way this could be simplified:
const char *
guestfs_last_error (guestfs_h *g)
{
- return g->last_error;
+ const char *r;
+
+ ACQUIRE_LOCK (g);
+ r = unlocked_last_error (g);
+ RELEASE_LOCK (g);
+ return r;
+}
(picking this because it is the first ACQUIRE_LOCK ... RELEASE_LOCK
pattern in the patch)
there could be an extra macro to do a "stack lock", using the cleanup
attribute we use already; something like:
static inline guestfs_h *acquire_lock (guestfs_h *g)
{
ACQUIRE_LOCK (g);
return g;
}
static inline void cleanup_release_lock (void *ptr)
{
guestfs_h *g = * (guestfs_h **) ptr;
RELEASE_LOCK (g);
}
#define STACK_LOCK (g) \
__attribute__((cleanup(cleanup_release_lock))) \
guestfs_h *_stack_lock_ = acquire_lock (g)
then the function above could look like:
const char *
guestfs_last_error (guestfs_h *g)
{
STACK_LOCK (g);
return g->last_error;
}
This would have the drawback of requiring __attribute__((cleanup)) to
work, although that could mean we could drop the code handling its
lack.
--
Pino Toscano