diff options
Diffstat (limited to 'thread_pthread.c')
| -rw-r--r-- | thread_pthread.c | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/thread_pthread.c b/thread_pthread.c index 04e938e647..f80776dbc8 100644 --- a/thread_pthread.c +++ b/thread_pthread.c @@ -2016,6 +2016,27 @@ ubf_ppoll_sleep(void *ignore) } /* + * Single CPU setups benefit from explicit sched_yield() before ppoll(), + * since threads may be too starved to enter the GVL waitqueue for + * us to detect contention. Instead, we want to kick other threads + * so they can run and possibly prevent us from entering slow paths + * in ppoll() or similar syscalls. + * + * Confirmed on FreeBSD 11.2 and Linux 4.19. + * [ruby-core:90417] [Bug #15398] + */ +#define GVL_UNLOCK_BEGIN_YIELD(th) do { \ + const native_thread_data_t *next; \ + rb_vm_t *vm = th->vm; \ + RB_GC_SAVE_MACHINE_CONTEXT(th); \ + rb_native_mutex_lock(&vm->gvl.lock); \ + next = gvl_release_common(vm); \ + rb_native_mutex_unlock(&vm->gvl.lock); \ + if (!next && vm_living_thread_num(vm) > 1) { \ + native_thread_yield(); \ + } + +/* * This function does not exclusively acquire sigwait_fd, so it * cannot safely read from it. However, it can be woken up in * 4 ways: @@ -2032,7 +2053,8 @@ native_ppoll_sleep(rb_thread_t *th, rb_hrtime_t *rel) th->unblock.func = ubf_ppoll_sleep; rb_native_mutex_unlock(&th->interrupt_lock); - GVL_UNLOCK_BEGIN(th); + GVL_UNLOCK_BEGIN_YIELD(th); + if (!RUBY_VM_INTERRUPTED(th->ec)) { struct pollfd pfd[2]; struct timespec ts; @@ -2066,7 +2088,7 @@ native_sleep(rb_thread_t *th, rb_hrtime_t *rel) th->unblock.func = ubf_sigwait; rb_native_mutex_unlock(&th->interrupt_lock); - GVL_UNLOCK_BEGIN(th); + GVL_UNLOCK_BEGIN_YIELD(th); if (!RUBY_VM_INTERRUPTED(th->ec)) { rb_sigwait_sleep(th, sigwait_fd, rel); |