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From: Muttley@DastardlyHQ.org
Newsgroups: comp.unix.programmer
Subject: Re: signal handling issues
Date: Fri, 31 Jan 2025 09:15:39 -0000 (UTC)
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On Thu, 30 Jan 2025 19:49:58 -0000 (UTC)
Kaz Kylheku <643-408-1753@kylheku.com> wibbled:
>On 2025-01-30, Scott Lurndal <scott@slp53.sl.home> wrote:
>> Rainer Weikusat <rweikusat@talktalk.net> writes:
>>>	If the process is multi-threaded, or if the process is
>>>	single-threaded and a signal handler is executed other than as
>>>	the result of:
>>
>> While Geoff may chime in with the definitive answer, once
>> multithreading was introduced, the stdio library functions
>> were required to synchronize access to the underlying
>> FILE buffers between threads.
>
>But the requirement applies to a single-threaded program in
>which an asynchronous signal occurs.
>
>The multi-threaded case seems to say that if the program is MT,
>then if a signal occurs even as a result of the program
>calling raise, etc, it is effectivecly an async signal
>(since it happens as the result of a thread executing
>asynchronously with regard to whatever thread catches the signal
>via a handler.)

All this confusion and complexity is why I always recommend that in a 
multithreaded program if you must use signals then all signals should be
blocked with a single thread dedicated to sitting in sigwait() and handling
whatever comes along.