Re: [rfc/remote] Tell remote stubs which signals are boring

Mark Kettenis
2006-10-25T21:33:24Z

> Date: Wed, 25 Oct 2006 17:24:41 -0400
> From: Daniel Jacobowitz <drow@false.org>
>
> Some time ago, I got a bug report that gdbserver couldn't be used to
> debug a program. You'd tell it to "continue", and it wouldn't - it
> would just spin in place.
>
> We realized eventually that the problem was SIGALRM. There was a tiny
> signal handler running every timer tick (at about 100Hz, if I remember
> right). That's plenty of time for native GDB to notice, resume, and
> let the code run. But if you have to stop the program, including any
> threads, and send a packet over a socket to another machine, only to
> have GDB tell you that you're not interested in it anyway, then you
> never make any progress. By the time the program returns from its
> signal handler, SIGALRM is pending again.
>
> This is the solution I came up with for that problem, adjusted to HEAD
> and given a more sensible packet name. I have a tested implementation
> of this patch for HEAD, if my remote protocol choices are acceptable.
> The new mechanism is completely transparent to the user.
>
> All comments welcome!

Makes sense to me. There are native targets too that support
something similar; on Solaris you can tell the kernel what signals
you're interested in, and GDB will not even get the signals that are
"nostop noprint pass".

I hope someone who is more familiar with the remote protocol can say
something sane about the syntax you chose for the QPassSignals packet.

Mark