Re: [PATCH v2 00/16] Interrupting programs that block/ignore SIGINT

[Pedro Alves <pedro@palves.net>]

On 2021-06-24 7:12 p.m., Konstantin Kharlamov wrote:
> Hello! I was referred to your patchset from #gdb IRC channel. Presumably,
> someone asked for real world usecases, but I haven't found that question. So I'm
> replying to the top message.

Hi!

> 
> I was recently fixing some bug in Pipewire. To be exact, I was working on
> `pipewire-media-session` (one of daemons that Pipewire is comprised of). Process
> of debugging basically included setting breakpoints somewhere, then hopefully
> triggering the breakpoint, then inspecting the state. Nothing unusual.
> 
> So, the thing that was slowing me down and annoying is that I couldn't just
> pause the debuggee through the usual means of ^C, then add a breakpoint.
> Pressing ^C was causing the process to exit!
> 
> Pipewire project seems to have a number of various daemons, and all of them set
> SIGINT handlers (judging by git-grepping for SIGINT). So basically, it is hard
> to debug Pipewire with GDB due to GDB not being able to interactively pause the
> process.
> 
> Now, I tested the patchset, and I confirm it solves the problem! GDB built from
> the palves' branch pauses pipewire-media-session correctly on ^C!

Awesome!

> With that said, I'm not sure if you need/use that in GDB project, but in any
> case, the series is:
> 
> 	Tested-by: Konstantin Kharlamov <hi-angel@yandex.ru>

We don't typically use it, but it doesn't hurt either!

> FYI, Tom Tromey mentioned¹ that the problem arises when debuggee uses either
> sigwait and signalfd. With git-grep I haven't found matches for sigwait in
> Pipewire, but I found ones for signalfd. I see your top message does not mention
> that your patchset also fixes situation for signalfd usage — but it seems it
> does. So, just for your interest, your patchset might fix even more problems
> than you expected ☺

Ahah, yeah.  Thanks, I didn't remember signalfd.  :-)