From 943bf37b10599d585f368c1f8d2e738b6ed8e98c Mon Sep 17 00:00:00 2001 From: normal Date: Mon, 27 Aug 2018 17:17:08 +0000 Subject: thread_pthread.c: avoid lock ping-pong in do_gvl_timer & ubf_select This simplifies the locking logic somewhat. While we're at it, designate_timer_thread is worthless in ubf_select because gvl_acquire_common already guarantees there is a gvl.timer if gvl->waitq is populated. In the future (for auto-fiber), this will allow using th->unblock.func for rb_waitpid callers (via rb_sigchld_handler). git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64575 b2dd03c8-39d4-4d8f-98ff-823fe69b080e --- thread_pthread.c | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) diff --git a/thread_pthread.c b/thread_pthread.c index a12619f92a..ef3cecb0e2 100644 --- a/thread_pthread.c +++ b/thread_pthread.c @@ -188,15 +188,15 @@ do_gvl_timer(rb_vm_t *vm, rb_thread_t *th) static rb_hrtime_t abs; native_thread_data_t *nd = &th->native_thread_data; + vm->gvl.timer = th; + /* take over wakeups from UBF_TIMER */ ubf_timer_disarm(); if (vm->gvl.timer_err == ETIMEDOUT) { abs = native_cond_timeout(&nd->cond.gvlq, TIME_QUANTUM_NSEC); } - vm->gvl.timer = th; vm->gvl.timer_err = native_cond_timedwait(&nd->cond.gvlq, &vm->gvl.lock, &abs); - vm->gvl.timer = 0; ubf_wakeup_all_threads(); ruby_sigchld_handler(vm); @@ -205,11 +205,7 @@ do_gvl_timer(rb_vm_t *vm, rb_thread_t *th) RUBY_VM_SET_TRAP_INTERRUPT(th->ec); } else { - /* unlock is needed because threadptr_trap_interrupt may - * call ubf_select which also acquires vm->gvl.lock */ - rb_native_mutex_unlock(&vm->gvl.lock); threadptr_trap_interrupt(vm->main_thread); - rb_native_mutex_lock(&vm->gvl.lock); } } @@ -218,6 +214,7 @@ do_gvl_timer(rb_vm_t *vm, rb_thread_t *th) * thread is contending for GVL: */ if (vm->gvl.acquired) timer_thread_function(); + vm->gvl.timer = 0; } static void @@ -1329,16 +1326,17 @@ ubf_select(void *ptr) /* * ubf_wakeup_thread() doesn't guarantee to wake up a target thread. * Therefore, we repeatedly call ubf_wakeup_thread() until a target thread - * exit from ubf function. We must designate a timer-thread to perform - * this operation. + * exit from ubf function. We must have a timer to perform this operation. + * We use double-checked locking here because this function may be called + * while vm->gvl.lock is held in do_gvl_timer */ - rb_native_mutex_lock(&vm->gvl.lock); - if (!vm->gvl.timer) { - if (!designate_timer_thread(vm)) { + if (vm->gvl.timer != ruby_thread_from_native()) { + rb_native_mutex_lock(&vm->gvl.lock); + if (!vm->gvl.timer) { rb_thread_wakeup_timer_thread(-1); } + rb_native_mutex_unlock(&vm->gvl.lock); } - rb_native_mutex_unlock(&vm->gvl.lock); ubf_wakeup_thread(th); } -- cgit v1.2.3