From: Eric Wong <e@80x24.org>
Date: Wed, 27 Nov 2019 01:33:33 +0000 (+0000)
Subject: httpd|nntpd: avoid missed signal wakeups
X-Git-Tag: v1.3.0~249
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=d6674af04cb74a4efd513d938bed8bf7ab2838eb;hp=d6674af04cb74a4efd513d938bed8bf7ab2838eb;p=public-inbox.git

httpd|nntpd: avoid missed signal wakeups

Our attempt at using a self-pipe in signal handlers was
ineffective, since pure Perl code execution is deferred
and Perl doesn't use an internal self-pipe/eventfd.  In
retrospect, I actually prefer the simplicity of Perl in
this regard...

We can use sigprocmask() from Perl, so we can introduce
signalfd(2) and EVFILT_SIGNAL support on Linux and *BSD-based
systems, respectively.  These OS primitives allow us to avoid a
race where Perl checks for signals right before epoll_wait() or
kevent() puts the process to sleep.

The (few) systems nowadays without signalfd(2) or IO::KQueue
will now see wakeups every second to avoid missed signals.
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