Re: [RFC][PATCH v2 1/2][PR gdb/24069] [delete] Not-so-harmless spurious call to `wait4`

[Simon Marchi via Gdb-patches <gdb-patches@sourceware.org>]

On 2022-02-16 09:15, Philippe Blain wrote:
> From: Dominique Quatravaux <dominique.quatravaux@epfl.ch>
> 
> As seen in https://sourceware.org/bugzilla/show_bug.cgi?id=24069 this
> code will typically wait4() a second time on the same process that was
> already wait4()'d a few lines above. While this used to be
> harmless/idempotent (when we assumed that the process already exited),
> this now causes a deadlock in the WIFSTOPPED case.
> 
> The early (~2019) history of bug #24069 cautiously suggests to use
> WNOHANG instead of outright deleting the call. However, tests on the
> current version of Darwin (Big Sur) demonstrate that gdb runs just
> fine without a redundant call to wait4(), as would be expected.
> Notwithstanding the debatable value of conserving bug compatibility
> with an OS release that is more than a decade old, there is scant
> evidence of what that double-wait4() was supposed to achieve in the
> first place - A cursory investigation with `git blame` pinpoints
> commits bb00b29d7802 and a80b95ba67e2 from the 2008-2009 era, but
> fails to answer the “why” question conclusively.

Given that this additional wait does not seem logical at all and
empirical evidence shows that it's not right, I'm fine with merging
this one directly.  Do you have push access, or would you like me to do
it on your behalf?

Simon