Re: [Patch] Broken multi-process detach

Pedro Alves
2012-07-16T17:49:57Z

On 07/16/2012 02:54 PM, Marc Khouzam wrote:
> Hi,
>
> Detaching from an inferior in multi-process is broken.
> The problem seems to be that in linux_nat.c:linux_nat_detach()
> GDB first unregisters from the event loop by calling
> linux_nat_async (NULL, 0). In multi-process, further
> events received from running inferiors are missed; breakpoint
> hits are not reported, interrupting a thread is not reported,
> and so on. See below for a broken session example.
>
> We could remove the call to linux_nat_async (NULL, 0) but I didn't
> know if that would have bad side-effects. Here is the patch that
> does that, if it is felt that is the correct solution.

I'm not thinking of any. Looks like I added it in the first
async mode version of linux-nat.c (which was much rewritten
later on). Let's remove it.

Remove also the target_async call below:

if (forks_exist_p ())
{
/* Multi-fork case. The current inferior_ptid is being detached
from, but there are other viable forks to debug. Detach from
the current fork, and context-switch to the first
available. */
linux_fork_detach (args, from_tty);

if (non_stop && target_can_async_p ())
target_async (inferior_event_handler, 0);

as this was re-installing the target on the event loop if there were
other checkpoints (checkpoint/info checkpoint) to debug. It is now
unnecessary if we don't unregister from the event loop in the first place.

>
> The testsuite hangs on HEAD so I wasn't able to run it yet.
> But I'll do so once it works again.

It doesn't hang for me. I've tested the patch on x86_64 Fedora 17, both
sync and async modes. No regressions.

Thanks!

--
Pedro Alves