diff options
Diffstat (limited to 'thread_pthread.c')
| -rw-r--r-- | thread_pthread.c | 87 |
1 files changed, 58 insertions, 29 deletions
diff --git a/thread_pthread.c b/thread_pthread.c index 6b5d624f66..1f2cff3b12 100644 --- a/thread_pthread.c +++ b/thread_pthread.c @@ -43,11 +43,28 @@ /* * UBF_TIMER and ubf_list both use SIGVTALRM. - * UBF_TIMER is to close TOCTTOU signal race on programs - * without GVL contention blocking read/write to sockets. * - * ubf_list wakeups may be triggered periodically by UBF_TIMER on - * gvl_yield. + * UBF_TIMER has NOTHING to do with thread timeslices (TIMER_INTERRUPT_MASK) + * + * UBF_TIMER is to close TOCTTOU signal race on programs where we + * cannot rely on GVL contention (vm->gvl.timer) to perform wakeups + * while a thread is doing blocking I/O on sockets or pipes. With + * rb_thread_call_without_gvl and similar functions: + * + * (1) Check interrupts. + * (2) release GVL. + * (2a) signal received + * (3) call func with data1 (blocks for a long time without ubf_timer) + * (4) acquire GVL. + * Other Ruby threads can not run in parallel any more. + * (5) Check interrupts. + * + * We need UBF_TIMER to break out of (3) if (2a) happens. + * + * ubf_list wakeups may be triggered on gvl_yield. + * + * If we have vm->gvl.timer (on GVL contention), we don't need UBF_TIMER + * as it can perform the same tasks while doing timeslices. */ #define UBF_TIMER_NONE 0 #define UBF_TIMER_POSIX 1 @@ -154,6 +171,37 @@ designate_timer_thread(rb_vm_t *vm) return FALSE; } +/* + * We become designated timer thread to kick vm->gvl.acquired + * periodically. Continue on old timeout if it expired. + */ +static void +do_gvl_timer(rb_vm_t *vm, rb_thread_t *th) +{ + static struct timespec ts; + static int err = ETIMEDOUT; + native_thread_data_t *nd = &th->native_thread_data; + + /* take over wakeups from UBF_TIMER */ + ubf_timer_disarm(); + + if (err == ETIMEDOUT) { + ts.tv_sec = 0; + ts.tv_nsec = TIME_QUANTUM_NSEC; + ts = native_cond_timeout(&nd->cond.gvlq, ts); + } + vm->gvl.timer = th; + err = native_cond_timedwait(&nd->cond.gvlq, &vm->gvl.lock, &ts); + vm->gvl.timer = 0; + ubf_wakeup_all_threads(); + + /* + * Timeslice. Warning: the process may fork while this + * thread is contending for GVL: + */ + if (vm->gvl.acquired) timer_thread_function(); +} + static void gvl_acquire_common(rb_vm_t *vm, rb_thread_t *th) { @@ -164,33 +212,10 @@ gvl_acquire_common(rb_vm_t *vm, rb_thread_t *th) "we must not be in ubf_list and GVL waitq at the same time"); list_add_tail(&vm->gvl.waitq, &nd->node.gvl); + do { if (!vm->gvl.timer) { - static struct timespec ts; - static int err = ETIMEDOUT; - - /* take over wakeups from UBF_TIMER */ - ubf_timer_disarm(); - - /* - * become designated timer thread to kick vm->gvl.acquired - * periodically. Continue on old timeout if it expired: - */ - if (err == ETIMEDOUT) { - ts.tv_sec = 0; - ts.tv_nsec = TIME_QUANTUM_NSEC; - ts = native_cond_timeout(&nd->cond.gvlq, ts); - } - vm->gvl.timer = th; - err = native_cond_timedwait(&nd->cond.gvlq, &vm->gvl.lock, &ts); - vm->gvl.timer = 0; - ubf_wakeup_all_threads(); - - /* - * Timeslice. Warning: the process may fork while this - * thread is contending for GVL: - */ - if (vm->gvl.acquired) timer_thread_function(); + do_gvl_timer(vm, th); } else { rb_native_cond_wait(&nd->cond.gvlq, &vm->gvl.lock); @@ -1368,6 +1393,10 @@ rb_thread_wakeup_timer_thread_fd(int fd) } } +/* + * This ensures we get a SIGVTALRM in TIME_QUANTUM_MSEC if our + * process could not react to the original signal in time. + */ static void ubf_timer_arm(rb_pid_t current) /* async signal safe */ { |