From ce2a3b40ed06a25e9292dd7d02b311510d0ba8e2 Mon Sep 17 00:00:00 2001
From: normal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sat, 30 Jun 2018 00:51:57 +0000
Subject: [PATCH] use SIGCHLD_LOSSY to enable waitpid polling mode

Some systems lack SIGCHLD or have incomplete SIGCHLD
implementations.  So enable polling mode for them.

[ruby-core:87705] [Bug #14867]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63795 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 mjit.c           |  2 +-
 process.c        |  2 +-
 signal.c         |  2 +-
 thread_pthread.c | 10 ++++++++++
 vm_core.h        |  7 +++++++
 5 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/mjit.c b/mjit.c
index e166a066bf..fb4b153cc3 100644
--- a/mjit.c
+++ b/mjit.c
@@ -408,7 +408,7 @@ exec_process(const char *path, char *const argv[])
 {
     int stat, exit_code = -2;
     pid_t pid;
-    rb_vm_t *vm = RUBY_SIGCHLD ? GET_VM() : 0;
+    rb_vm_t *vm = (RUBY_SIGCHLD || SIGCHLD_LOSSY) ? GET_VM() : 0;
     rb_nativethread_cond_t cond;
 
     if (vm) {
diff --git a/process.c b/process.c
index 08986f9ede..ef0523165e 100644
--- a/process.c
+++ b/process.c
@@ -1126,7 +1126,7 @@ rb_waitpid(rb_pid_t pid, int *st, int flags)
     waitpid_state_init(&w, pid, flags);
     w.ec = GET_EC();
 
-    if (RUBY_SIGCHLD) {
+    if (RUBY_SIGCHLD || SIGCHLD_LOSSY) {
         waitpid_wait(&w);
     }
     else {
diff --git a/signal.c b/signal.c
index a817cb336a..7b725d8268 100644
--- a/signal.c
+++ b/signal.c
@@ -1066,7 +1066,7 @@ void ruby_waitpid_all(rb_vm_t *); /* process.c */
 void
 ruby_sigchld_handler(rb_vm_t *vm)
 {
-    if (ATOMIC_EXCHANGE(sigchld_hit, 0)) {
+    if (SIGCHLD_LOSSY || ATOMIC_EXCHANGE(sigchld_hit, 0)) {
         ruby_waitpid_all(vm);
     }
 }
diff --git a/thread_pthread.c b/thread_pthread.c
index 6ac7728ad9..401fc0c774 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1375,6 +1375,16 @@ timer_thread_sleep(rb_global_vm_lock_t* gvl)
 
     need_polling = !ubf_threads_empty();
 
+    if (SIGCHLD_LOSSY && !need_polling) {
+        rb_vm_t *vm = container_of(gvl, rb_vm_t, gvl);
+
+        rb_native_mutex_lock(&vm->waitpid_lock);
+        if (!list_empty(&vm->waiting_pids) || !list_empty(&vm->waiting_grps)) {
+            need_polling = 1;
+        }
+        rb_native_mutex_unlock(&vm->waitpid_lock);
+    }
+
     if (gvl->waiting > 0 || need_polling) {
 	/* polling (TIME_QUANTUM_USEC usec) */
 	result = poll(pollfds, 1, TIME_QUANTUM_USEC/1000);
diff --git a/vm_core.h b/vm_core.h
index bdbe87287b..9db99fe03b 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -100,6 +100,13 @@
 #  define RUBY_SIGCHLD    (0)
 #endif
 
+/* platforms with broken or non-existent SIGCHLD work by polling */
+#if defined(__APPLE__) || defined(__WIN32__)
+#  define SIGCHLD_LOSSY (1)
+#else
+#  define SIGCHLD_LOSSY (0)
+#endif
+
 #ifdef HAVE_STDARG_PROTOTYPES
 #include <stdarg.h>
 #define va_init_list(a,b) va_start((a),(b))