As mentioned in a05fe6684a, glibc provides two
wrappers for epoll_pwait2() on 32-bit architectures, and sys/epoll.h,
together with features-time64.h, selects the appropriate one.
To avoid depending on symbols introduced in newer glibc releases, that
commit relied on the glibc internal macro __USE_TIME_BITS64 to determine
which wrapper to use. However, that is incorrect on some architectures.
See:
https://sourceware.org/git/?p=glibc.git;a=commit;h=a4ed0471d71739928a0d0fa3258b3ff3b158e9b9
The above glibc commit introduces a new internal macro,
__USE_TIME64_REDIRECTS, which correctly describes whether the time64
wrapper should be used. However, we cannot rely on it because it was
introduced in glibc 2.40, while our baseline remains glibc 2.34.
Moreover, even after raising the baseline, relying on glibc internal
implementation details is undesirable.
Instead, call the epoll_pwait2 syscall directly. This avoids any
dependency on glibc wrapper selection logic while preserving the original
goal of avoiding newer glibc symbols.
As a side effect, this also enables epoll_pwait2() on musl, which does not
currently provide a libc wrapper for it.
Currently, epoll_pwait2() is only used by sd-event, so this is also the
simplest solution.
Yu Watanabe
a2de89f622