thread_pthread.c (native_ppoll_sleep): new eventfd (or pipe) for ubf
Relying on ubf_select + ubf_list for main thread is not guaranteed to wake a process up as it does not acquire sigwait_fd and all other threads may be sleeping. native_cond_sleep and the sigwait_fd path are immune to TOCTOU issues, but native_ppoll_sleep may have its wakeup stolen by sigwait_fd sleeper and the RUBY_VM_INTERRUPTED check is insufficient.
Note: for pthreads platforms without POSIX timers, this becomes more expensive than Ruby 2.5, as six pipe FDs come into use. Linux is best off with only two descriptors for eventfd.
thread_pthread.c (native_ppoll_sleep): new eventfd (or pipe) for ubf
Relying on ubf_select + ubf_list for main thread is not
guaranteed to wake a process up as it does not acquire
sigwait_fd and all other threads may be sleeping.
native_cond_sleep and the sigwait_fd path are immune to TOCTOU
issues, but native_ppoll_sleep may have its wakeup stolen
by sigwait_fd sleeper and the RUBY_VM_INTERRUPTED check is
insufficient.
Note: for pthreads platforms without POSIX timers, this becomes
more expensive than Ruby 2.5, as six pipe FDs come into use.
Linux is best off with only two descriptors for eventfd.
[ruby-core:89655]
cf. http://ci.rvm.jp/results/trunk-mjit@silicon-docker/1437559
http://ci.rvm.jp/results/trunk-mjit-wait@silicon-docker/1437673
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65495 b2dd03c8-39d4-4d8f-98ff-823fe69b080e