Simon McVittie authored Dec 18, 2017 and Simon McVittie committed Nov 06, 2018

Closures use a 16-bit atomic reference count, which is really slow
on certain ARM64 CPUs such as the Cortex-A57 (#1316). This is
non-trivial to solve, since the public struct field cannot be enlarged
to 32-bit while preserving ABI, and 16-bit atomic operations would be new
(and rather niche) API.

Until this can be solved properly (hopefully in GLib 2.59.x), cut down
the number of signal emission cycles and bump up the timeout in the
Meson build system, so that builds won't time out. We can't just take
another zero off the number of signal emission cycles, as was done in the
original version of this patch in Debian, because if we do that it can
result in test failures when the main thread starves the other threads.

ARM64 CPUs are backwards-compatible with 32-bit ARM, and the same
slowdown can be seen when building and testing 32-bit code on these
CPUs, so check for both 32- and 64-bit ARM.

Bug-Debian: https://bugs.debian.org/880883


Co-authored-by: Iain Lane <laney@debian.org>
Signed-off-by: Simon McVittie <smcv@debian.org>