normal	2018-08-16 17:26:56 +0900 (Thu, 16 Aug 2018)

  New Revision: 64389

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=64389

  Log:
    thread_pthread.c: reduce ubf_timer arming for non-signal wakeups
    
    We do not need to rely on SIGVTALRM for non-sighandler wakeups.
    This will reduce spurious wakeups in cases where sigwait_fd
    is not grabbed again, soon.

  Modified files:
    trunk/process.c
    trunk/thread_pthread.c
Index: thread_pthread.c
===================================================================
--- thread_pthread.c	(revision 64388)
+++ thread_pthread.c	(revision 64389)
@@ -247,7 +247,7 @@ gvl_acquire_common(rb_vm_t *vm, rb_threa https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L247
     vm->gvl.acquired = th;
     if (!vm->gvl.timer) {
         if (!designate_timer_thread(vm) && !ubf_threads_empty()) {
-            rb_thread_wakeup_timer_thread(0);
+            rb_thread_wakeup_timer_thread(-1);
         }
     }
 }
@@ -1324,10 +1324,10 @@ ubf_select(void *ptr) https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1324
      * exit from ubf function.  We must designate a timer-thread to perform
      * this operation.
      */
-   rb_native_mutex_lock(&vm->gvl.lock);
-   if (!vm->gvl.timer) {
+    rb_native_mutex_lock(&vm->gvl.lock);
+    if (!vm->gvl.timer) {
         if (!designate_timer_thread(vm)) {
-            rb_thread_wakeup_timer_thread(0);
+            rb_thread_wakeup_timer_thread(-1);
         }
     }
     rb_native_mutex_unlock(&vm->gvl.lock);
@@ -1416,7 +1416,8 @@ static void https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1416
 ubf_timer_arm(rb_pid_t current) /* async signal safe */
 {
 #if UBF_TIMER == UBF_TIMER_POSIX
-    if (timer_posix.owner == current && !ATOMIC_CAS(timer_posix.armed, 0, 1)) {
+    if ((!current || timer_posix.owner == current) &&
+            !ATOMIC_CAS(timer_posix.armed, 0, 1)) {
         struct itimerspec it;
 
         it.it_interval.tv_sec = it.it_value.tv_sec = 0;
@@ -1446,7 +1447,7 @@ ubf_timer_arm(rb_pid_t current) /* async https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1447
         }
     }
 #elif UBF_TIMER == UBF_TIMER_PTHREAD
-    if (current == timer_pthread.owner) {
+    if (!current || current == timer_pthread.owner) {
         if (ATOMIC_EXCHANGE(timer_pthread.armed, 1) == 0)
             rb_thread_wakeup_timer_thread_fd(timer_pthread.low[1]);
     }
@@ -1456,8 +1457,19 @@ ubf_timer_arm(rb_pid_t current) /* async https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1457
 void
 rb_thread_wakeup_timer_thread(int sig)
 {
+    rb_pid_t current;
+
+    /* non-sighandler path */
+    if (sig <= 0) {
+        rb_thread_wakeup_timer_thread_fd(signal_self_pipe.normal[1]);
+        if (sig < 0) {
+            ubf_timer_arm(0);
+        }
+        return;
+    }
+
     /* must be safe inside sighandler, so no mutex */
-    rb_pid_t current = getpid();
+    current = getpid();
     if (signal_self_pipe.owner_process == current) {
         rb_thread_wakeup_timer_thread_fd(signal_self_pipe.normal[1]);
 
@@ -1465,7 +1477,7 @@ rb_thread_wakeup_timer_thread(int sig) https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1477
          * system_working check is required because vm and main_thread are
          * freed during shutdown
          */
-        if (sig && system_working > 0) {
+        if (system_working > 0) {
             volatile rb_execution_context_t *ec;
             rb_vm_t *vm = GET_VM();
             rb_thread_t *mth;
@@ -1485,9 +1497,6 @@ rb_thread_wakeup_timer_thread(int sig) https://github.com/ruby/ruby/blob/trunk/thread_pthread.c#L1497
                 RUBY_VM_SET_TRAP_INTERRUPT(ec);
                 ubf_timer_arm(current);
             }
-	}
-        else if (sig == 0 && system_working > 0) {
-            ubf_timer_arm(current);
         }
     }
 }
Index: process.c
===================================================================
--- process.c	(revision 64388)
+++ process.c	(revision 64389)
@@ -1162,6 +1162,10 @@ waitpid_nogvl(void *x) https://github.com/ruby/ruby/blob/trunk/process.c#L1162
             /* another thread calling rb_sigwait_sleep will process
              * signals for us */
             if (SIGCHLD_LOSSY) {
+                /*
+                 * XXX this may not be needed anymore with new GVL
+                 * and sigwait_fd usage
+                 */
                 rb_thread_wakeup_timer_thread(0);
             }
             rb_native_cond_wait(w->cond, &th->interrupt_lock);

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