[PATCH] gdb: iterate only on vfork parent threads in handle_vfork_child_exec_or_exit

[John Baldwin]

On 8/5/21 9:21 AM, Simon Marchi via Gdb-patches wrote:
> I spotted what I think is a buglet in proceed_after_vfork_done.  After a
> vfork child exits or execs, we resume all the threads of the parent.  To
> do so, we iterate on all threads using iterate_over_threads with the
> proceed_after_vfork_done callback.  Each thread is resumed if the
> following condition is true:
> 
>      if (thread->ptid.pid () == pid
> 	&& thread->state == THREAD_RUNNING
> 	&& !thread->executing
> 	&& !thread->stop_requested
> 	&& thread->stop_signal () == GDB_SIGNAL_0)
> 
> where `pid` is the pid of the vfork parent.  This is not multi-target
> aware: since it only filters on pid, if there is an inferior with the
> same pid in another target, we could end up resuming a thread of that
> other inferior.  The chances of the stars aligning for this to happen
> are tiny, but still.
> 
> Fix that by iterating only on the vfork parent's threads, instead of on
> all threads.  This is more efficient, as we iterate on just the required
> threads (inferiors have their own thread list), and we can drop the pid
> check.  The resulting code is also more straightforward in my opinion,
> so it's a win-win.

This looks sensible to me.

-- 
John Baldwin