normal	2018-06-30 07:13:02 +0900 (Sat, 30 Jun 2018)

  New Revision: 63793

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=63793

  Log:
    signal.c: use ATOMIC_EXCHANGE for sigchld_hit
    
    sig_atomic_t may not be sufficient for multi-threaded
    applications if the sighandler runs on a different CPU
    than timer thread.

  Modified files:
    trunk/signal.c
Index: signal.c
===================================================================
--- signal.c	(revision 63792)
+++ signal.c	(revision 63793)
@@ -692,7 +692,7 @@ signal_enque(int sig) https://github.com/ruby/ruby/blob/trunk/signal.c#L692
     ATOMIC_INC(signal_buff.size);
 }
 
-static sig_atomic_t sigchld_hit;
+static rb_atomic_t sigchld_hit;
 
 /* Prevent compiler from reordering access */
 #define ACCESS_ONCE(type,x) (*((volatile type *)&(x)))
@@ -705,7 +705,7 @@ sighandler(int sig) https://github.com/ruby/ruby/blob/trunk/signal.c#L705
     /* the VM always needs to handle SIGCHLD for rb_waitpid */
     if (sig == RUBY_SIGCHLD) {
         rb_vm_t *vm = GET_VM();
-        sigchld_hit = 1;
+        ATOMIC_EXCHANGE(sigchld_hit, 1);
 
         /* avoid spurious wakeup in main thread iff nobody uses trap(:CHLD) */
         if (vm && ACCESS_ONCE(VALUE, vm->trap_list.cmd[sig])) {
@@ -1066,8 +1066,7 @@ void ruby_waitpid_all(rb_vm_t *); /* pro https://github.com/ruby/ruby/blob/trunk/signal.c#L1066
 void
 ruby_sigchld_handler(rb_vm_t *vm)
 {
-    if (sigchld_hit) {
-        sigchld_hit = 0;
+    if (ATOMIC_EXCHANGE(sigchld_hit, 0)) {
         ruby_waitpid_all(vm);
     }
 }

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