unrevert r63852 but keep SIGCHLD path disabled for win32

Reading win32/win32.c waitpid implementation, maybe waitpid(-1, ...)
on that platform will never conflict with mjit use of waitpid.

In any case, I've added WAITPID_USE_SIGCHLD macro to vm_core.h
so it can be easy for Linux/BSD users to test (hopefully!)
win32-compatible code.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63855 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

16 files changed, 627 insertions, 230 deletions

diff --git a/configure.ac b/configure.ac
index b433863d64..074a3fd394 100644
--- a/configure.ac
+++ b/configure.ac
@@ -766,6 +766,7 @@ AS_CASE(["$target_os"],
 		AS_IF([test $gcc_major -lt 4 -o \( $gcc_major -eq 4 -a $gcc_minor -lt 3 \)], [
 		    ac_cv_func___builtin_setjmp=no
 		])
+		with_setjmp_type=sigsetjmp # to hijack SIGCHLD handler
 		AC_CACHE_CHECK(for broken crypt with 8bit chars, rb_cv_broken_crypt,
 		    [AC_TRY_RUN([
 #include <stdio.h>
@@ -1782,6 +1783,7 @@ AC_CHECK_FUNCS(getsid)
 AC_CHECK_FUNCS(gettimeofday)		# for making ac_cv_func_gettimeofday
 AC_CHECK_FUNCS(getuidx)
 AC_CHECK_FUNCS(gmtime_r)
+AC_CHECK_FUNCS(grantpt)
 AC_CHECK_FUNCS(initgroups)
 AC_CHECK_FUNCS(ioctl)
 AC_CHECK_FUNCS(isfinite)
diff --git a/ext/pty/pty.c b/ext/pty/pty.c
index b3c7535321..1ac89061c1 100644
--- a/ext/pty/pty.c
+++ b/ext/pty/pty.c
@@ -246,19 +246,13 @@ get_device_once(int *master, int *slave, char SlaveName[DEVICELEN], int nomesg,
     /* Unix98 PTY */
     int masterfd = -1, slavefd = -1;
     char *slavedevice;
-    struct sigaction dfl, old;
-
-    dfl.sa_handler = SIG_DFL;
-    dfl.sa_flags = 0;
-    sigemptyset(&dfl.sa_mask);
 
 #if defined(__sun) || (defined(__FreeBSD__) && __FreeBSD_version < 902000)
     /* workaround for Solaris 10: grantpt() doesn't work if FD_CLOEXEC is set.  [ruby-dev:44688] */
     /* FreeBSD 9.2 or later supports O_CLOEXEC
      * http://www.freebsd.org/cgi/query-pr.cgi?pr=162374 */
     if ((masterfd = posix_openpt(O_RDWR|O_NOCTTY)) == -1) goto error;
-    if (sigaction(SIGCHLD, &dfl, &old) == -1) goto error;
-    if (grantpt(masterfd) == -1) goto grantpt_error;
+    if (rb_grantpt(masterfd) == -1) goto error;
     rb_fd_fix_cloexec(masterfd);
 #else
     {
@@ -272,10 +266,8 @@ get_device_once(int *master, int *slave, char SlaveName[DEVICELEN], int nomesg,
 	if ((masterfd = posix_openpt(flags)) == -1) goto error;
     }
     rb_fd_fix_cloexec(masterfd);
-    if (sigaction(SIGCHLD, &dfl, &old) == -1) goto error;
-    if (grantpt(masterfd) == -1) goto grantpt_error;
+    if (rb_grantpt(masterfd) == -1) goto error;
 #endif
-    if (sigaction(SIGCHLD, &old, NULL) == -1) goto error;
     if (unlockpt(masterfd) == -1) goto error;
     if ((slavedevice = ptsname(masterfd)) == NULL) goto error;
     if (no_mesg(slavedevice, nomesg) == -1) goto error;
@@ -293,8 +285,6 @@ get_device_once(int *master, int *slave, char SlaveName[DEVICELEN], int nomesg,
     strlcpy(SlaveName, slavedevice, DEVICELEN);
     return 0;
 
-  grantpt_error:
-    sigaction(SIGCHLD, &old, NULL);
   error:
     if (slavefd != -1) close(slavefd);
     if (masterfd != -1) close(masterfd);
@@ -346,21 +336,17 @@ get_device_once(int *master, int *slave, char SlaveName[DEVICELEN], int nomesg,
 
     extern char *ptsname(int);
     extern int unlockpt(int);
-    extern int grantpt(int);
 
 #if defined(__sun)
     /* workaround for Solaris 10: grantpt() doesn't work if FD_CLOEXEC is set.  [ruby-dev:44688] */
     if((masterfd = open("/dev/ptmx", O_RDWR, 0)) == -1) goto error;
-    s = signal(SIGCHLD, SIG_DFL);
-    if(grantpt(masterfd) == -1) goto error;
+    if(rb_grantpt(masterfd) == -1) goto error;
     rb_fd_fix_cloexec(masterfd);
 #else
     if((masterfd = rb_cloexec_open("/dev/ptmx", O_RDWR, 0)) == -1) goto error;
     rb_update_max_fd(masterfd);
-    s = signal(SIGCHLD, SIG_DFL);
-    if(grantpt(masterfd) == -1) goto error;
+    if(rb_grantpt(masterfd) == -1) goto error;
 #endif
-    signal(SIGCHLD, s);
     if(unlockpt(masterfd) == -1) goto error;
     if((slavedevice = ptsname(masterfd)) == NULL) goto error;
     if (no_mesg(slavedevice, nomesg) == -1) goto error;
diff --git a/internal.h b/internal.h
index 59e855c850..b555bbab06 100644
--- a/internal.h
+++ b/internal.h
@@ -2042,6 +2042,9 @@ VALUE rb_gcd_normal(VALUE self, VALUE other);
 VALUE rb_gcd_gmp(VALUE x, VALUE y);
 #endif
 
+/* signal.c (export) */
+int rb_grantpt(int fd);
+
 /* string.c (export) */
 #ifdef RUBY_ENCODING_H
 /* internal use */
diff --git a/mjit.c b/mjit.c
index 07e9328aff..ade1e2e6a9 100644
--- a/mjit.c
+++ b/mjit.c
@@ -80,6 +80,7 @@
 #include "constant.h"
 #include "id_table.h"
 #include "ruby_assert.h"
+#include "ruby/thread.h"
 #include "ruby/util.h"
 #include "ruby/version.h"
 
@@ -118,6 +119,10 @@ extern void rb_native_cond_wait(rb_nativethread_cond_t *cond, rb_nativethread_lo
 
 extern int rb_thread_create_mjit_thread(void (*child_hook)(void), void (*worker_func)(void));
 
+/* process.c */
+rb_pid_t ruby_waitpid_locked(rb_vm_t *, rb_pid_t, int *status, int options,
+                          rb_nativethread_cond_t *cond);
+
 #define RB_CONDATTR_CLOCK_MONOTONIC 1
 
 #ifdef _WIN32
@@ -263,7 +268,7 @@ real_ms_time(void)
 static int
 sprint_uniq_filename(char *str, size_t size, unsigned long id, const char *prefix, const char *suffix)
 {
-    return snprintf(str, size, "%s/%sp%luu%lu%s", tmp_dir, prefix, (unsigned long) getpid(), id, suffix);
+    return snprintf(str, size, "%s/%sp%"PRI_PIDT_PREFIX"uu%lu%s", tmp_dir, prefix, getpid(), id, suffix);
 }
 
 /* Return an unique file name in /tmp with PREFIX and SUFFIX and
@@ -401,22 +406,41 @@ start_process(const char *path, char *const *argv)
 static int
 exec_process(const char *path, char *const argv[])
 {
-    int stat, exit_code;
+    int stat, exit_code = -2;
     pid_t pid;
+    rb_vm_t *vm = WAITPID_USE_SIGCHLD ? GET_VM() : 0;
+    rb_nativethread_cond_t cond;
 
-    pid = start_process(path, argv);
-    if (pid <= 0)
-        return -2;
+    if (vm) {
+        rb_native_cond_initialize(&cond);
+        rb_native_mutex_lock(&vm->waitpid_lock);
+    }
 
-    for (;;) {
-        waitpid(pid, &stat, 0);
-        if (WIFEXITED(stat)) {
-            exit_code = WEXITSTATUS(stat);
-            break;
-        } else if (WIFSIGNALED(stat)) {
-            exit_code = -1;
+    pid = start_process(path, argv);
+    for (;pid > 0;) {
+        pid_t r = vm ? ruby_waitpid_locked(vm, pid, &stat, 0, &cond)
+                     : waitpid(pid, &stat, 0);
+        if (r == -1) {
+            if (errno == EINTR) continue;
+            fprintf(stderr, "[%"PRI_PIDT_PREFIX"d] waitpid(%"PRI_PIDT_PREFIX"d): %s (SIGCHLD=%d,%u)\n",
+                    getpid(), pid, strerror(errno),
+                    RUBY_SIGCHLD, SIGCHLD_LOSSY);
             break;
         }
+        else if (r == pid) {
+            if (WIFEXITED(stat)) {
+                exit_code = WEXITSTATUS(stat);
+                break;
+            } else if (WIFSIGNALED(stat)) {
+                exit_code = -1;
+                break;
+            }
+        }
+    }
+
+    if (vm) {
+        rb_native_mutex_unlock(&vm->waitpid_lock);
+        rb_native_cond_destroy(&cond);
     }
     return exit_code;
 }
@@ -1491,12 +1515,15 @@ mjit_init(struct mjit_options *opts)
 static void
 stop_worker(void)
 {
+    rb_execution_context_t *ec = GET_EC();
+
     stop_worker_p = TRUE;
     while (!worker_stopped) {
         verbose(3, "Sending cancel signal to worker");
         CRITICAL_SECTION_START(3, "in stop_worker");
         rb_native_cond_broadcast(&mjit_worker_wakeup);
         CRITICAL_SECTION_FINISH(3, "in stop_worker");
+        RUBY_VM_CHECK_INTS(ec);
     }
 }
 
diff --git a/process.c b/process.c
index 12ea6eac86..12cceba934 100644
--- a/process.c
+++ b/process.c
@@ -885,12 +885,6 @@ pst_wcoredump(VALUE st)
 #endif
 }
 
-struct waitpid_arg {
-    rb_pid_t pid;
-    int flags;
-    int *st;
-};
-
 static rb_pid_t
 do_waitpid(rb_pid_t pid, int *st, int flags)
 {
@@ -903,45 +897,263 @@ do_waitpid(rb_pid_t pid, int *st, int flags)
 #endif
 }
 
+struct waitpid_state {
+    struct list_node wnode;
+    rb_execution_context_t *ec;
+    rb_nativethread_cond_t *cond;
+    rb_pid_t ret;
+    rb_pid_t pid;
+    int status;
+    int options;
+    int errnum;
+};
+
+void rb_native_mutex_lock(rb_nativethread_lock_t *);
+void rb_native_mutex_unlock(rb_nativethread_lock_t *);
+void rb_native_cond_signal(rb_nativethread_cond_t *);
+void rb_native_cond_wait(rb_nativethread_cond_t *, rb_nativethread_lock_t *);
+rb_nativethread_cond_t *rb_sleep_cond_get(const rb_execution_context_t *);
+void rb_sleep_cond_put(rb_nativethread_cond_t *);
+
+static void
+waitpid_notify(struct waitpid_state *w, rb_pid_t ret)
+{
+    w->ret = ret;
+    list_del_init(&w->wnode);
+    rb_native_cond_signal(w->cond);
+}
+
+#ifdef _WIN32 /* for spawnvp result from mjit.c */
+#  define waitpid_sys(pid,status,options) \
+	  (WaitForSingleObject((HANDLE)(pid), 0),\
+	   GetExitCodeProcess((HANDLE)(pid), (LPDWORD)(status)))
+#else
+#  define waitpid_sys(pid,status,options) do_waitpid((pid),(status),(options))
+#endif
+
+/* called by timer thread */
+static void
+waitpid_each(struct list_head *head)
+{
+    struct waitpid_state *w = 0, *next;
+
+    list_for_each_safe(head, w, next, wnode) {
+        rb_pid_t ret;
+
+        if (w->ec)
+            ret = do_waitpid(w->pid, &w->status, w->options | WNOHANG);
+        else
+            ret = waitpid_sys(w->pid, &w->status, w->options | WNOHANG);
+
+        if (!ret) continue;
+        if (ret == -1) w->errnum = errno;
+
+        if (w->ec) { /* rb_waitpid */
+            rb_thread_t *th = rb_ec_thread_ptr(w->ec);
+
+            rb_native_mutex_lock(&th->interrupt_lock);
+            waitpid_notify(w, ret);
+            rb_native_mutex_unlock(&th->interrupt_lock);
+        }
+        else { /* ruby_waitpid_locked */
+            waitpid_notify(w, ret);
+        }
+    }
+}
+
+void
+ruby_waitpid_all(rb_vm_t *vm)
+{
+    rb_native_mutex_lock(&vm->waitpid_lock);
+    waitpid_each(&vm->waiting_pids);
+    if (list_empty(&vm->waiting_pids)) {
+        waitpid_each(&vm->waiting_grps);
+    }
+    rb_native_mutex_unlock(&vm->waitpid_lock);
+}
+
+static void
+waitpid_state_init(struct waitpid_state *w, rb_pid_t pid, int options)
+{
+    w->ret = 0;
+    w->pid = pid;
+    w->options = options;
+}
+
+/*
+ * must be called with vm->waitpid_lock held, this is not interruptible
+ */
+rb_pid_t
+ruby_waitpid_locked(rb_vm_t *vm, rb_pid_t pid, int *status, int options,
+                    rb_nativethread_cond_t *cond)
+{
+    struct waitpid_state w;
+
+    assert(!ruby_thread_has_gvl_p() && "must not have GVL");
+
+    waitpid_state_init(&w, pid, options);
+    if (w.pid > 0 || list_empty(&vm->waiting_pids))
+        w.ret = do_waitpid(w.pid, &w.status, w.options | WNOHANG);
+    if (w.ret) {
+        if (w.ret == -1) w.errnum = errno;
+    }
+    else {
+        w.cond = cond;
+        w.ec = 0;
+        list_add(w.pid > 0 ? &vm->waiting_pids : &vm->waiting_grps, &w.wnode);
+        do {
+            rb_native_cond_wait(w.cond, &vm->waitpid_lock);
+        } while (!w.ret);
+        list_del(&w.wnode);
+    }
+    if (status) {
+        *status = w.status;
+    }
+    if (w.ret == -1) errno = w.errnum;
+    return w.ret;
+}
+
+static void
+waitpid_wake(void *x)
+{
+    struct waitpid_state *w = x;
+
+    /* th->interrupt_lock is already held by rb_threadptr_interrupt_common */
+    rb_native_cond_signal(w->cond);
+}
+
 static void *
-rb_waitpid_blocking(void *data)
+waitpid_nogvl(void *x)
 {
-    struct waitpid_arg *arg = data;
-    rb_pid_t result = do_waitpid(arg->pid, arg->st, arg->flags);
-    return (void *)(VALUE)result;
+    struct waitpid_state *w = x;
+    rb_thread_t *th = rb_ec_thread_ptr(w->ec);
+
+    rb_native_mutex_lock(&th->interrupt_lock);
+    /*
+     * We must check again before waiting, timer-thread may change w->ret
+     * by the time we enter this.  And we may also be interrupted.
+     */
+    if (!w->ret && !RUBY_VM_INTERRUPTED_ANY(w->ec)) {
+        if (SIGCHLD_LOSSY) {
+            rb_thread_wakeup_timer_thread();
+        }
+        rb_native_cond_wait(w->cond, &th->interrupt_lock);
+    }
+    rb_native_mutex_unlock(&th->interrupt_lock);
+
+    return 0;
 }
 
-static rb_pid_t
-do_waitpid_nonblocking(rb_pid_t pid, int *st, int flags)
+static VALUE
+waitpid_sleep(VALUE x)
 {
-    void *result;
-    struct waitpid_arg arg;
-    arg.pid = pid;
-    arg.st = st;
-    arg.flags = flags;
-    result = rb_thread_call_without_gvl(rb_waitpid_blocking, &arg,
-					RUBY_UBF_PROCESS, 0);
-    return (rb_pid_t)(VALUE)result;
+    struct waitpid_state *w = (struct waitpid_state *)x;
+
+    while (!w->ret) {
+        rb_thread_call_without_gvl(waitpid_nogvl, w, waitpid_wake, w);
+    }
+
+    return Qfalse;
+}
+
+static VALUE
+waitpid_cleanup(VALUE x)
+{
+    struct waitpid_state *w = (struct waitpid_state *)x;
+
+    if (w->ret == 0) {
+        rb_vm_t *vm = rb_ec_vm_ptr(w->ec);
+
+        rb_native_mutex_lock(&vm->waitpid_lock);
+        list_del(&w->wnode);
+        rb_native_mutex_unlock(&vm->waitpid_lock);
+    }
+    rb_sleep_cond_put(w->cond);
+
+    return Qfalse;
+}
+
+static void
+waitpid_wait(struct waitpid_state *w)
+{
+    rb_vm_t *vm = rb_ec_vm_ptr(w->ec);
+
+    /*
+     * Lock here to prevent do_waitpid from stealing work from the
+     * ruby_waitpid_locked done by mjit workers since mjit works
+     * outside of GVL
+     */
+    rb_native_mutex_lock(&vm->waitpid_lock);
+
+    if (w->pid > 0 || list_empty(&vm->waiting_pids))
+        w->ret = do_waitpid(w->pid, &w->status, w->options | WNOHANG);
+    if (w->ret) {
+        w->cond = 0;
+        if (w->ret == -1) w->errnum = errno;
+    }
+    else if (w->options & WNOHANG) {
+        w->cond = 0;
+    }
+    else {
+        w->cond = rb_sleep_cond_get(w->ec);
+        /* order matters, favor specified PIDs rather than -1 or 0 */
+        list_add(w->pid > 0 ? &vm->waiting_pids : &vm->waiting_grps, &w->wnode);
+    }
+
+    rb_native_mutex_unlock(&vm->waitpid_lock);
+
+    if (w->cond) {
+        rb_ensure(waitpid_sleep, (VALUE)w, waitpid_cleanup, (VALUE)w);
+    }
+}
+
+static void *
+waitpid_blocking_no_SIGCHLD(void *x)
+{
+    struct waitpid_state *w = x;
+
+    w->ret = do_waitpid(w->pid, &w->status, w->options);
+
+    return 0;
+}
+
+static void
+waitpid_no_SIGCHLD(struct waitpid_state *w)
+{
+    if (w->options & WNOHANG) {
+        w->ret = do_waitpid(w->pid, &w->status, w->options);
+    }
+    else {
+        do {
+            rb_thread_call_without_gvl(waitpid_blocking_no_SIGCHLD, w,
+                                       RUBY_UBF_PROCESS, 0);
+        } while (w->ret < 0 && errno == EINTR && (RUBY_VM_CHECK_INTS(w->ec),1));
+    }
+    if (w->ret == -1)
+        w->errnum = errno;
 }
 
 rb_pid_t
 rb_waitpid(rb_pid_t pid, int *st, int flags)
 {
-    rb_pid_t result;
+    struct waitpid_state w;
 
-    if (flags & WNOHANG) {
-	result = do_waitpid(pid, st, flags);
+    waitpid_state_init(&w, pid, flags);
+    w.ec = GET_EC();
+
+    if (WAITPID_USE_SIGCHLD) {
+        waitpid_wait(&w);
     }
     else {
-	while ((result = do_waitpid_nonblocking(pid, st, flags)) < 0 &&
-	       (errno == EINTR)) {
-	    RUBY_VM_CHECK_INTS(GET_EC());
-	}
+        waitpid_no_SIGCHLD(&w);
     }
-    if (result > 0) {
-	rb_last_status_set(*st, result);
+
+    if (st) *st = w.status;
+    if (w.ret > 0) {
+	rb_last_status_set(w.status, w.ret);
     }
-    return result;
+    if (w.ret == -1) errno = w.errnum;
+    return w.ret;
 }
 
 
@@ -3595,6 +3807,8 @@ disable_child_handler_fork_child(struct child_handler_disabler_state *old, char
 	}
     }
 
+    /* non-Ruby child process, ensure cmake can see SIGCHLD */
+    sigemptyset(&old->sigmask);
     ret = sigprocmask(SIG_SETMASK, &old->sigmask, NULL); /* async-signal-safe */
     if (ret != 0) {
         ERRMSG("sigprocmask");
@@ -4086,16 +4300,6 @@ rb_f_system(int argc, VALUE *argv)
     VALUE execarg_obj;
     struct rb_execarg *eargp;
 
-#if defined(SIGCLD) && !defined(SIGCHLD)
-# define SIGCHLD SIGCLD
-#endif
-
-#ifdef SIGCHLD
-    RETSIGTYPE (*chfunc)(int);
-
-    rb_last_status_clear();
-    chfunc = signal(SIGCHLD, SIG_DFL);
-#endif
     execarg_obj = rb_execarg_new(argc, argv, TRUE, TRUE);
     pid = rb_execarg_spawn(execarg_obj, NULL, 0);
 #if defined(HAVE_WORKING_FORK) || defined(HAVE_SPAWNV)
@@ -4106,9 +4310,6 @@ rb_f_system(int argc, VALUE *argv)
             rb_sys_fail("Another thread waited the process started by system().");
     }
 #endif
-#ifdef SIGCHLD
-    signal(SIGCHLD, chfunc);
-#endif
     TypedData_Get_Struct(execarg_obj, struct rb_execarg, &exec_arg_data_type, eargp);
     if (pid < 0) {
         if (eargp->exception) {
diff --git a/signal.c b/signal.c
index d2231fe5ca..e9f0708510 100644
--- a/signal.c
+++ b/signal.c
@@ -62,10 +62,6 @@ ruby_atomic_compare_and_swap(rb_atomic_t *ptr, rb_atomic_t cmp,
 }
 #endif
 
-#ifndef NSIG
-# define NSIG (_SIGMAX + 1)      /* For QNX */
-#endif
-
 #define FOREACH_SIGNAL(sig, offset) \
     for (sig = siglist + (offset); sig < siglist + numberof(siglist); ++sig)
 enum { LONGEST_SIGNAME = 7 }; /* MIGRATE and RETRACT */
@@ -132,15 +128,9 @@ static const struct signals {
 #ifdef SIGCONT
     {"CONT", SIGCONT},
 #endif
-#ifdef SIGCHLD
-    {"CHLD", SIGCHLD},
-#endif
-#ifdef SIGCLD
-    {"CLD", SIGCLD},
-#else
-# ifdef SIGCHLD
-    {"CLD", SIGCHLD},
-# endif
+#if RUBY_SIGCHLD
+    {"CHLD", RUBY_SIGCHLD },
+    {"CLD", RUBY_SIGCHLD },
 #endif
 #ifdef SIGTTIN
     {"TTIN", SIGTTIN},
@@ -708,12 +698,29 @@ signal_enque(int sig)
     ATOMIC_INC(signal_buff.size);
 }
 
+static rb_atomic_t sigchld_hit;
+
+/* Prevent compiler from reordering access */
+#define ACCESS_ONCE(type,x) (*((volatile type *)&(x)))
+
 static RETSIGTYPE
 sighandler(int sig)
 {
     int old_errnum = errno;
 
-    signal_enque(sig);
+    /* the VM always needs to handle SIGCHLD for rb_waitpid */
+    if (sig == RUBY_SIGCHLD) {
+        rb_vm_t *vm = GET_VM();
+        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])) {
+            signal_enque(sig);
+        }
+    }
+    else {
+        signal_enque(sig);
+    }
     rb_thread_wakeup_timer_thread();
 #if !defined(BSD_SIGNAL) && !defined(POSIX_SIGNAL)
     ruby_signal(sig, sighandler);
@@ -748,6 +755,7 @@ rb_enable_interrupt(void)
 #ifdef HAVE_PTHREAD_SIGMASK
     sigset_t mask;
     sigemptyset(&mask);
+    sigaddset(&mask, RUBY_SIGCHLD); /* timer-thread handles this */
     pthread_sigmask(SIG_SETMASK, &mask, NULL);
 #endif
 }
@@ -1058,6 +1066,17 @@ rb_trap_exit(void)
     }
 }
 
+void ruby_waitpid_all(rb_vm_t *); /* process.c */
+
+/* only runs in the timer-thread */
+void
+ruby_sigchld_handler(rb_vm_t *vm)
+{
+    if (SIGCHLD_LOSSY || ATOMIC_EXCHANGE(sigchld_hit, 0)) {
+        ruby_waitpid_all(vm);
+    }
+}
+
 void
 rb_signal_exec(rb_thread_t *th, int sig)
 {
@@ -1124,6 +1143,9 @@ default_handler(int sig)
 #ifdef SIGUSR2
       case SIGUSR2:
 #endif
+#if RUBY_SIGCHLD
+      case RUBY_SIGCHLD:
+#endif
         func = sighandler;
         break;
 #ifdef SIGBUS
@@ -1161,6 +1183,9 @@ trap_handler(VALUE *cmd, int sig)
     VALUE command;
 
     if (NIL_P(*cmd)) {
+	if (sig == RUBY_SIGCHLD) {
+	    goto sig_dfl;
+	}
 	func = SIG_IGN;
     }
     else {
@@ -1181,6 +1206,9 @@ trap_handler(VALUE *cmd, int sig)
 		break;
               case 14:
 		if (memcmp(cptr, "SYSTEM_DEFAULT", 14) == 0) {
+                    if (sig == RUBY_SIGCHLD) {
+                        goto sig_dfl;
+                    }
                     func = SIG_DFL;
                     *cmd = 0;
 		}
@@ -1188,6 +1216,9 @@ trap_handler(VALUE *cmd, int sig)
 	      case 7:
 		if (memcmp(cptr, "SIG_IGN", 7) == 0) {
 sig_ign:
+                    if (sig == RUBY_SIGCHLD) {
+                        goto sig_dfl;
+                    }
                     func = SIG_IGN;
                     *cmd = Qtrue;
 		}
@@ -1274,7 +1305,7 @@ trap(int sig, sighandler_t func, VALUE command)
 	break;
     }
 
-    vm->trap_list.cmd[sig] = command;
+    ACCESS_ONCE(VALUE, vm->trap_list.cmd[sig]) = command;
     vm->trap_list.safe[sig] = rb_safe_level();
 
     return oldcmd;
@@ -1419,20 +1450,18 @@ install_sighandler(int signum, sighandler_t handler)
 #  define install_sighandler(signum, handler) \
     INSTALL_SIGHANDLER(install_sighandler(signum, handler), #signum, signum)
 
-#if defined(SIGCLD) || defined(SIGCHLD)
+#if RUBY_SIGCHLD
 static int
 init_sigchld(int sig)
 {
     sighandler_t oldfunc;
+    sighandler_t func = sighandler;
 
     oldfunc = ruby_signal(sig, SIG_DFL);
     if (oldfunc == SIG_ERR) return -1;
-    if (oldfunc != SIG_DFL && oldfunc != SIG_IGN) {
-	ruby_signal(sig, oldfunc);
-    }
-    else {
-	GET_VM()->trap_list.cmd[sig] = 0;
-    }
+    ruby_signal(sig, func);
+    ACCESS_ONCE(VALUE, GET_VM()->trap_list.cmd[sig]) = 0;
+
     return 0;
 }
 
@@ -1548,11 +1577,55 @@ Init_signal(void)
     install_sighandler(SIGSYS, sig_do_nothing);
 #endif
 
-#if defined(SIGCLD)
-    init_sigchld(SIGCLD);
-#elif defined(SIGCHLD)
-    init_sigchld(SIGCHLD);
+#if RUBY_SIGCHLD
+    init_sigchld(RUBY_SIGCHLD);
 #endif
 
     rb_enable_interrupt();
 }
+
+#if defined(HAVE_GRANTPT)
+extern int grantpt(int);
+#else
+static int
+fake_grantfd(int masterfd)
+{
+    errno = ENOSYS;
+    return -1;
+}
+#define grantpt(fd) fake_grantfd(fd)
+#endif
+
+int
+rb_grantpt(int masterfd)
+{
+    if (RUBY_SIGCHLD) {
+        rb_vm_t *vm = GET_VM();
+        int ret, e;
+
+        /*
+         * Prevent waitpid calls from Ruby by taking waitpid_lock.
+         * Pedantically, grantpt(3) is undefined if a non-default
+         * SIGCHLD handler is defined, but preventing conflicting
+         * waitpid calls ought to be sufficient.
+         *
+         * We could install the default sighandler temporarily, but that
+         * could cause SIGCHLD to be missed by other threads.  Blocking
+         * SIGCHLD won't work here, either, unless we stop and restart
+         * timer-thread (as only timer-thread sees SIGCHLD), but that
+         * seems like overkill.
+         */
+        rb_nativethread_lock_lock(&vm->waitpid_lock);
+        {
+            ret = grantpt(masterfd); /* may spawn `pt_chown' and wait on it */
+            if (ret < 0) e = errno;
+        }
+        rb_nativethread_lock_unlock(&vm->waitpid_lock);
+
+        if (ret < 0) errno = e;
+        return ret;
+    }
+    else {
+        return grantpt(masterfd);
+    }
+}
diff --git a/spec/ruby/core/process/wait2_spec.rb b/spec/ruby/core/process/wait2_spec.rb
index 3f5aa3c7e2..d0163f80af 100644
--- a/spec/ruby/core/process/wait2_spec.rb
+++ b/spec/ruby/core/process/wait2_spec.rb
@@ -4,31 +4,37 @@ describe "Process.wait2" do
   before :all do
     # HACK: this kludge is temporarily necessary because some
     # misbehaving spec somewhere else does not clear processes
+    # Note: background processes are unavoidable with MJIT,
+    # but we shouldn't reap them from Ruby-space
     begin
       Process.wait(-1, Process::WNOHANG)
-      $stderr.puts "Leaked process before wait2 specs! Waiting for it"
+      without_feature :mjit do
+        $stderr.puts "Leaked process before wait2 specs! Waiting for it"
+      end
       leaked = Process.waitall
-      $stderr.puts "leaked before wait2 specs: #{leaked}"
+      $stderr.puts "leaked before wait2 specs: #{leaked}" unless leaked.empty?
+      with_feature :mjit do
+        # Ruby-space should not see PIDs used by mjit
+        leaked.should be_empty
+      end
     rescue Errno::ECHILD # No child processes
     rescue NotImplementedError
     end
   end
 
-  without_feature :mjit do # [Bug #14867]
-    platform_is_not :windows do
-      it "returns the pid and status of child process" do
-        pidf = Process.fork { Process.exit! 99 }
-        results = Process.wait2
-        results.size.should == 2
-        pidw, status = results
-        pidf.should == pidw
-        status.exitstatus.should == 99
-      end
+  platform_is_not :windows do
+    it "returns the pid and status of child process" do
+      pidf = Process.fork { Process.exit! 99 }
+      results = Process.wait2
+      results.size.should == 2
+      pidw, status = results
+      pidf.should == pidw
+      status.exitstatus.should == 99
     end
+  end
 
-    it "raises a StandardError if no child processes exist" do
-      lambda { Process.wait2 }.should raise_error(Errno::ECHILD)
-      lambda { Process.wait2 }.should raise_error(StandardError)
-    end
+  it "raises a StandardError if no child processes exist" do
+    lambda { Process.wait2 }.should raise_error(Errno::ECHILD)
+    lambda { Process.wait2 }.should raise_error(StandardError)
   end
 end
diff --git a/spec/ruby/core/process/wait_spec.rb b/spec/ruby/core/process/wait_spec.rb
index 447c62f42a..5130bb4391 100644
--- a/spec/ruby/core/process/wait_spec.rb
+++ b/spec/ruby/core/process/wait_spec.rb
@@ -8,85 +8,87 @@ describe "Process.wait" do
     begin
       leaked = Process.waitall
       puts "leaked before wait specs: #{leaked}" unless leaked.empty?
+      with_feature :mjit do
+        # Ruby-space should not see PIDs used by mjit
+        leaked.should be_empty
+      end
     rescue NotImplementedError
     end
   end
 
-  without_feature :mjit do # [Bug #14867]
-    it "raises an Errno::ECHILD if there are no child processes" do
-      lambda { Process.wait }.should raise_error(Errno::ECHILD)
+  it "raises an Errno::ECHILD if there are no child processes" do
+    lambda { Process.wait }.should raise_error(Errno::ECHILD)
+  end
+
+  platform_is_not :windows do
+    it "returns its childs pid" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      Process.wait.should == pid
     end
 
-    platform_is_not :windows do
-      it "returns its childs pid" do
-        pid = Process.spawn(ruby_cmd('exit'))
-        Process.wait.should == pid
-      end
+    it "sets $? to a Process::Status" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      Process.wait
+      $?.should be_kind_of(Process::Status)
+      $?.pid.should == pid
+    end
 
-      it "sets $? to a Process::Status" do
-        pid = Process.spawn(ruby_cmd('exit'))
-        Process.wait
-        $?.should be_kind_of(Process::Status)
-        $?.pid.should == pid
-      end
+    it "waits for any child process if no pid is given" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      Process.wait.should == pid
+      lambda { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
+    end
 
-      it "waits for any child process if no pid is given" do
-        pid = Process.spawn(ruby_cmd('exit'))
-        Process.wait.should == pid
-        lambda { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
-      end
+    it "waits for a specific child if a pid is given" do
+      pid1 = Process.spawn(ruby_cmd('exit'))
+      pid2 = Process.spawn(ruby_cmd('exit'))
+      Process.wait(pid2).should == pid2
+      Process.wait(pid1).should == pid1
+      lambda { Process.kill(0, pid1) }.should raise_error(Errno::ESRCH)
+      lambda { Process.kill(0, pid2) }.should raise_error(Errno::ESRCH)
+    end
 
-      it "waits for a specific child if a pid is given" do
-        pid1 = Process.spawn(ruby_cmd('exit'))
-        pid2 = Process.spawn(ruby_cmd('exit'))
-        Process.wait(pid2).should == pid2
-        Process.wait(pid1).should == pid1
-        lambda { Process.kill(0, pid1) }.should raise_error(Errno::ESRCH)
-        lambda { Process.kill(0, pid2) }.should raise_error(Errno::ESRCH)
-      end
+    it "coerces the pid to an Integer" do
+      pid1 = Process.spawn(ruby_cmd('exit'))
+      Process.wait(mock_int(pid1)).should == pid1
+      lambda { Process.kill(0, pid1) }.should raise_error(Errno::ESRCH)
+    end
 
-      it "coerces the pid to an Integer" do
-        pid1 = Process.spawn(ruby_cmd('exit'))
-        Process.wait(mock_int(pid1)).should == pid1
-        lambda { Process.kill(0, pid1) }.should raise_error(Errno::ESRCH)
-      end
+    # This spec is probably system-dependent.
+    it "waits for a child whose process group ID is that of the calling process" do
+      pid1 = Process.spawn(ruby_cmd('exit'), pgroup: true)
+      pid2 = Process.spawn(ruby_cmd('exit'))
 
-      # This spec is probably system-dependent.
-      it "waits for a child whose process group ID is that of the calling process" do
-        pid1 = Process.spawn(ruby_cmd('exit'), pgroup: true)
-        pid2 = Process.spawn(ruby_cmd('exit'))
+      Process.wait(0).should == pid2
+      Process.wait.should == pid1
+    end
 
-        Process.wait(0).should == pid2
-        Process.wait.should == pid1
+    # This spec is probably system-dependent.
+    it "doesn't block if no child is available when WNOHANG is used" do
+      read, write = IO.pipe
+      pid = Process.fork do
+        read.close
+        Signal.trap("TERM") { Process.exit! }
+        write << 1
+        write.close
+        sleep
       end
 
-      # This spec is probably system-dependent.
-      it "doesn't block if no child is available when WNOHANG is used" do
-        read, write = IO.pipe
-        pid = Process.fork do
-          read.close
-          Signal.trap("TERM") { Process.exit! }
-          write << 1
-          write.close
-          sleep
-        end
-
-        Process.wait(pid, Process::WNOHANG).should be_nil
+      Process.wait(pid, Process::WNOHANG).should be_nil
 
-        # wait for the child to setup its TERM handler
-        write.close
-        read.read(1)
-        read.close
+      # wait for the child to setup its TERM handler
+      write.close
+      read.read(1)
+      read.close
 
-        Process.kill("TERM", pid)
-        Process.wait.should == pid
-      end
+      Process.kill("TERM", pid)
+      Process.wait.should == pid
+    end
 
-      it "always accepts flags=0" do
-        pid = Process.spawn(ruby_cmd('exit'))
-        Process.wait(-1, 0).should == pid
-        lambda { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
-      end
+    it "always accepts flags=0" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      Process.wait(-1, 0).should == pid
+      lambda { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
     end
   end
 end
diff --git a/spec/ruby/core/process/waitall_spec.rb b/spec/ruby/core/process/waitall_spec.rb
index ff06ae21f9..bdc1ea7490 100644
--- a/spec/ruby/core/process/waitall_spec.rb
+++ b/spec/ruby/core/process/waitall_spec.rb
@@ -8,43 +8,41 @@ describe "Process.waitall" do
     end
   end
 
-  without_feature :mjit do # [Bug #14867]
-    it "returns an empty array when there are no children" do
-      Process.waitall.should == []
-    end
+  it "returns an empty array when there are no children" do
+    Process.waitall.should == []
+  end
 
-    it "takes no arguments" do
-      lambda { Process.waitall(0) }.should raise_error(ArgumentError)
-    end
+  it "takes no arguments" do
+    lambda { Process.waitall(0) }.should raise_error(ArgumentError)
+  end
 
-    platform_is_not :windows do
-      it "waits for all children" do
-        pids = []
-        pids << Process.fork { Process.exit! 2 }
-        pids << Process.fork { Process.exit! 1 }
-        pids << Process.fork { Process.exit! 0 }
-        Process.waitall
-        pids.each { |pid|
-          lambda { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
-        }
-      end
+  platform_is_not :windows do
+    it "waits for all children" do
+      pids = []
+      pids << Process.fork { Process.exit! 2 }
+      pids << Process.fork { Process.exit! 1 }
+      pids << Process.fork { Process.exit! 0 }
+      Process.waitall
+      pids.each { |pid|
+        lambda { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
+      }
+    end
 
-      it "returns an array of pid/status pairs" do
-        pids = []
-        pids << Process.fork { Process.exit! 2 }
-        pids << Process.fork { Process.exit! 1 }
-        pids << Process.fork { Process.exit! 0 }
-        a = Process.waitall
-        a.should be_kind_of(Array)
-        a.size.should == 3
-        pids.each { |pid|
-          pid_status = a.assoc(pid)
-          pid_status.should be_kind_of(Array)
-          pid_status.size.should == 2
-          pid_status.first.should == pid
-          pid_status.last.should be_kind_of(Process::Status)
-        }
-      end
+    it "returns an array of pid/status pairs" do
+      pids = []
+      pids << Process.fork { Process.exit! 2 }
+      pids << Process.fork { Process.exit! 1 }
+      pids << Process.fork { Process.exit! 0 }
+      a = Process.waitall
+      a.should be_kind_of(Array)
+      a.size.should == 3
+      pids.each { |pid|
+        pid_status = a.assoc(pid)
+        pid_status.should be_kind_of(Array)
+        pid_status.size.should == 2
+        pid_status.first.should == pid
+        pid_status.last.should be_kind_of(Process::Status)
+      }
     end
   end
 end
diff --git a/test/ruby/test_optimization.rb b/test/ruby/test_optimization.rb
index 6bfaf11d7f..32bdcef13d 100644
--- a/test/ruby/test_optimization.rb
+++ b/test/ruby/test_optimization.rb
@@ -707,7 +707,7 @@ class TestRubyOptimization < Test::Unit::TestCase
   end
 
   def test_clear_unreachable_keyword_args
-    assert_separately [], <<-END, timeout: 20
+    assert_separately [], <<-END, timeout: 30
       script =  <<-EOS
         if true
         else
diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index 36ae94908a..6a32702b03 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -1426,7 +1426,6 @@ class TestProcess < Test::Unit::TestCase
   end
 
   def test_wait_without_arg
-    skip "[Bug #14867]" if RubyVM::MJIT.enabled?
     with_tmpchdir do
       write_file("foo", "sleep 0.1")
       pid = spawn(RUBY, "foo")
@@ -1435,7 +1434,6 @@ class TestProcess < Test::Unit::TestCase
   end
 
   def test_wait2
-    skip "[Bug #14867]" if RubyVM::MJIT.enabled?
     with_tmpchdir do
       write_file("foo", "sleep 0.1")
       pid = spawn(RUBY, "foo")
@@ -1444,7 +1442,6 @@ class TestProcess < Test::Unit::TestCase
   end
 
   def test_waitall
-    skip "[Bug #14867]" if RubyVM::MJIT.enabled?
     with_tmpchdir do
       write_file("foo", "sleep 0.1")
       ps = (0...3).map { spawn(RUBY, "foo") }.sort
@@ -1459,7 +1456,9 @@ class TestProcess < Test::Unit::TestCase
   def test_wait_exception
     bug11340 = '[ruby-dev:49176] [Bug #11340]'
     t0 = t1 = nil
-    IO.popen([RUBY, '-e', 'puts;STDOUT.flush;Thread.start{gets;exit};sleep(3)'], 'r+') do |f|
+    sec = 3
+    code = "puts;STDOUT.flush;Thread.start{gets;exit};sleep(#{sec})"
+    IO.popen([RUBY, '-e', code], 'r+') do |f|
       pid = f.pid
       f.gets
       t0 = Time.now
@@ -1473,10 +1472,11 @@ class TestProcess < Test::Unit::TestCase
         th.kill.join
       end
       t1 = Time.now
+      diff = t1 - t0
+      assert_operator(diff, :<, sec,
+                  ->{"#{bug11340}: #{diff} seconds to interrupt Process.wait"})
       f.puts
     end
-    assert_operator(t1 - t0, :<, 3,
-                    ->{"#{bug11340}: #{t1-t0} seconds to interrupt Process.wait"})
   end
 
   def test_abort
diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index d67cdcb984..edd44ca0ae 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -1,6 +1,7 @@
 # -*- coding: us-ascii -*-
 require 'test/unit'
 
+require 'timeout'
 require 'tmpdir'
 require 'tempfile'
 require_relative '../lib/jit_support'
@@ -590,14 +591,18 @@ class TestRubyOptions < Test::Unit::TestCase
 
       pid = spawn(EnvUtil.rubybin, "test-script")
       ps = nil
+      now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      stop = now + 30
       begin
         sleep 0.1
         ps = `#{PSCMD.join(' ')} #{pid}`
         break if /hello world/ =~ ps
-      end until Process.wait(pid, Process::WNOHANG)
+        now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      end until Process.wait(pid, Process::WNOHANG) || now > stop
       assert_match(/hello world/, ps)
+      assert_operator now, :<, stop
       Process.kill :KILL, pid
-      Process.wait(pid)
+      Timeout.timeout(5) { Process.wait(pid) }
     end
   end
 
@@ -616,14 +621,18 @@ class TestRubyOptions < Test::Unit::TestCase
 
       pid = spawn(EnvUtil.rubybin, "test-script")
       ps = nil
+      now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      stop = now + 30
       begin
         sleep 0.1
         ps = `#{PSCMD.join(' ')} #{pid}`
         break if /hello world/ =~ ps
-      end until Process.wait(pid, Process::WNOHANG)
+        now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      end until Process.wait(pid, Process::WNOHANG) || now > stop
       assert_match(/hello world/, ps)
+      assert_operator now, :<, stop
       Process.kill :KILL, pid
-      Process.wait(pid)
+      Timeout.timeout(5) { Process.wait(pid) }
     end
   end
 
diff --git a/thread.c b/thread.c
index 5a5e32379d..c58d3e0b9d 100644
--- a/thread.c
+++ b/thread.c
@@ -413,6 +413,10 @@ rb_vm_gvl_destroy(rb_vm_t *vm)
     gvl_release(vm);
     gvl_destroy(vm);
     rb_native_mutex_destroy(&vm->thread_destruct_lock);
+    if (0) {
+        /* may be held by running threads */
+        rb_native_mutex_destroy(&vm->waitpid_lock);
+    }
 }
 
 void
@@ -4131,6 +4135,9 @@ rb_gc_set_stack_end(VALUE **stack_end_p)
 #endif
 
 
+/* signal.c */
+void ruby_sigchld_handler(rb_vm_t *);
+
 /*
  *
  */
@@ -4163,6 +4170,7 @@ timer_thread_function(void *arg)
     rb_native_mutex_unlock(&vm->thread_destruct_lock);
 
     /* check signal */
+    ruby_sigchld_handler(vm);
     rb_threadptr_check_signal(vm->main_thread);
 
 #if 0
@@ -4247,6 +4255,9 @@ rb_thread_atfork_internal(rb_thread_t *th, void (*atfork)(rb_thread_t *, const r
     }
     rb_vm_living_threads_init(vm);
     rb_vm_living_threads_insert(vm, th);
+
+    /* may be held by MJIT threads in parent */
+    rb_native_mutex_initialize(&vm->waitpid_lock);
     vm->fork_gen++;
 
     vm->sleeper = 0;
@@ -4999,6 +5010,7 @@ Init_Thread(void)
 	    gvl_init(th->vm);
 	    gvl_acquire(th->vm, th);
             rb_native_mutex_initialize(&th->vm->thread_destruct_lock);
+            rb_native_mutex_initialize(&th->vm->waitpid_lock);
             rb_native_mutex_initialize(&th->interrupt_lock);
 
 	    th->pending_interrupt_queue = rb_ary_tmp_new(0);
@@ -5302,3 +5314,25 @@ rb_uninterruptible(VALUE (*b_proc)(ANYARGS), VALUE data)
 
     return rb_ensure(b_proc, data, rb_ary_pop, cur_th->pending_interrupt_mask_stack);
 }
+
+#ifndef USE_NATIVE_SLEEP_COND
+#  define USE_NATIVE_SLEEP_COND (0)
+#endif
+
+#if !USE_NATIVE_SLEEP_COND
+rb_nativethread_cond_t *
+rb_sleep_cond_get(const rb_execution_context_t *ec)
+{
+    rb_nativethread_cond_t *cond = ALLOC(rb_nativethread_cond_t);
+    rb_native_cond_initialize(cond);
+
+    return cond;
+}
+
+void
+rb_sleep_cond_put(rb_nativethread_cond_t *cond)
+{
+    rb_native_cond_destroy(cond);
+    xfree(cond);
+}
+#endif /* !USE_NATIVE_SLEEP_COND */
diff --git a/thread_pthread.c b/thread_pthread.c
index 8a4825548b..722ce44487 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1369,7 +1369,7 @@ setup_communication_pipe(void)
  * @pre the calling context is in the timer thread.
  */
 static inline void
-timer_thread_sleep(rb_global_vm_lock_t* gvl)
+timer_thread_sleep(rb_vm_t *vm)
 {
     int result;
     int need_polling;
@@ -1382,7 +1382,15 @@ timer_thread_sleep(rb_global_vm_lock_t* gvl)
 
     need_polling = !ubf_threads_empty();
 
-    if (gvl->waiting > 0 || need_polling) {
+    if (SIGCHLD_LOSSY && !need_polling) {
+        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 (vm->gvl.waiting > 0 || need_polling) {
 	/* polling (TIME_QUANTUM_USEC usec) */
 	result = poll(pollfds, 1, TIME_QUANTUM_USEC/1000);
     }
@@ -1421,7 +1429,7 @@ static rb_nativethread_lock_t timer_thread_lock;
 static rb_nativethread_cond_t timer_thread_cond;
 
 static inline void
-timer_thread_sleep(rb_global_vm_lock_t* unused)
+timer_thread_sleep(rb_vm_t *unused)
 {
     struct timespec ts;
     ts.tv_sec = 0;
@@ -1485,7 +1493,14 @@ native_set_another_thread_name(rb_nativethread_id_t thread_id, VALUE name)
 static void *
 thread_timer(void *p)
 {
-    rb_global_vm_lock_t *gvl = (rb_global_vm_lock_t *)p;
+    rb_vm_t *vm = p;
+#ifdef HAVE_PTHREAD_SIGMASK /* mainly to enable SIGCHLD */
+    {
+        sigset_t mask;
+        sigemptyset(&mask);
+        pthread_sigmask(SIG_SETMASK, &mask, NULL);
+    }
+#endif
 
     if (TT_DEBUG) WRITE_CONST(2, "start timer thread\n");
 
@@ -1507,7 +1522,7 @@ thread_timer(void *p)
 	if (TT_DEBUG) WRITE_CONST(2, "tick\n");
 
         /* wait */
-	timer_thread_sleep(gvl);
+	timer_thread_sleep(vm);
     }
 #if USE_SLEEPY_TIMER_THREAD
     CLOSE_INVALIDATE(normal[0]);
@@ -1579,7 +1594,7 @@ rb_thread_create_timer_thread(void)
 	if (timer_thread.created) {
 	    rb_bug("rb_thread_create_timer_thread: Timer thread was already created\n");
 	}
-	err = pthread_create(&timer_thread.id, &attr, thread_timer, &vm->gvl);
+	err = pthread_create(&timer_thread.id, &attr, thread_timer, vm);
 	pthread_attr_destroy(&attr);
 
 	if (err == EINVAL) {
@@ -1590,7 +1605,7 @@ rb_thread_create_timer_thread(void)
 	     * default stack size is enough for them:
 	     */
 	    stack_size = 0;
-	    err = pthread_create(&timer_thread.id, NULL, thread_timer, &vm->gvl);
+	    err = pthread_create(&timer_thread.id, NULL, thread_timer, vm);
 	}
 	if (err != 0) {
 	    rb_warn("pthread_create failed for timer: %s, scheduling broken",
@@ -1771,4 +1786,22 @@ rb_thread_create_mjit_thread(void (*child_hook)(void), void (*worker_func)(void)
     return ret;
 }
 
+#define USE_NATIVE_SLEEP_COND (1)
+
+#if USE_NATIVE_SLEEP_COND
+rb_nativethread_cond_t *
+rb_sleep_cond_get(const rb_execution_context_t *ec)
+{
+    rb_thread_t *th = rb_ec_thread_ptr(ec);
+
+    return &th->native_thread_data.sleep_cond;
+}
+
+void
+rb_sleep_cond_put(rb_nativethread_cond_t *cond)
+{
+    /* no-op */
+}
+#endif /* USE_NATIVE_SLEEP_COND */
+
 #endif /* THREAD_SYSTEM_DEPENDENT_IMPLEMENTATION */
diff --git a/vm_core.h b/vm_core.h
index ee151195d5..10a697f8c5 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -92,6 +92,24 @@
 
 #define RUBY_NSIG NSIG
 
+#if defined(SIGCLD)
+#  define RUBY_SIGCHLD    (SIGCLD)
+#elif defined(SIGCHLD)
+#  define RUBY_SIGCHLD    (SIGCHLD)
+#else
+#  define RUBY_SIGCHLD    (0)
+#endif
+
+/* platforms with broken or non-existent SIGCHLD work by polling */
+#if defined(__APPLE__)
+#  define SIGCHLD_LOSSY (1)
+#else
+#  define SIGCHLD_LOSSY (0)
+#endif
+
+/* define to 0 to test old code path */
+#define WAITPID_USE_SIGCHLD (RUBY_SIGCHLD || SIGCHLD_LOSSY)
+
 #ifdef HAVE_STDARG_PROTOTYPES
 #include <stdarg.h>
 #define va_init_list(a,b) va_start((a),(b))
@@ -553,6 +571,9 @@ typedef struct rb_vm_struct {
 #endif
 
     rb_serial_t fork_gen;
+    rb_nativethread_lock_t waitpid_lock;
+    struct list_head waiting_pids; /* PID > 0: <=> struct waitpid_state */
+    struct list_head waiting_grps; /* PID <= 0: <=> struct waitpid_state */
     struct list_head waiting_fds; /* <=> struct waiting_fd */
     struct list_head living_threads;
     VALUE thgroup_default;
@@ -1561,6 +1582,8 @@ static inline void
 rb_vm_living_threads_init(rb_vm_t *vm)
 {
     list_head_init(&vm->waiting_fds);
+    list_head_init(&vm->waiting_pids);
+    list_head_init(&vm->waiting_grps);
     list_head_init(&vm->living_threads);
     vm->living_thread_num = 0;
 }
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index 20b47a581a..fd852c21b7 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -760,7 +760,7 @@ $(CONFIG_H): $(MKFILES) $(srcdir)/win32/Makefile.sub $(win_srcdir)/Makefile.sub
 #define ssize_t int
 !endif
 #define PRI_LL_PREFIX "I64"
-#define PRI_PIDT_PREFIX PRI_INT_PREFIX
+#define PRI_PIDT_PREFIX "I"
 #define GETGROUPS_T int
 #define RETSIGTYPE void
 #define TYPEOF_TIMEVAL_TV_SEC long