Re: [PATCH 0/4] Introduce scoped_ignore_signal & make it thread safe

[John Baldwin <jhb@FreeBSD.org>]

On 6/17/21 8:36 AM, Pedro Alves wrote:
> On 2021-06-17 3:38 p.m., Pedro Alves wrote:
>> On 2021-06-15 6:04 p.m., John Baldwin wrote:
> 
>> If SIGTTOU ends up raised by some other thread while the main thread has it blocked
>> in scoped_ignore_sigttou, and if it is sent to the whole process, there's a small time window
>> where the sigtimedwait in the main thread can eat the signal.  That still seems better than
>> the current status where the end result can be that we can end up with the signal enabled
>> instead of ignored and then gdb backgrounds itself.  This is of course highly theoretical since I
>> expect that gdb threads run with signals blocked from the get go.  But you never know what
>> Python code does.
>>
> 
> Hmm, I just thought of an easy fix for that.  Just don't consume the pending
> signal in SIGTTOU's case.  I wonder how portable is this?  WDYT?
> 
> I'll see if I can try this on Solaris.

I think this is ok.  I suspect that some of the rules around SIGTTOU are in POSIX as I
think job control is in POSIX, so (hopefully) the behavior there is fairly uniform.
I strongly suspect the other BSD's all follow FreeBSD at least, so if Solaris is the
same I'd feel pretty good about this behavior being consistent.

-- 
John Baldwin