Merge branch 'rickard/poll-wake/OTP-9019' into dev

* rickard/poll-wake/OTP-9019:
  Simplify erts_poll_wait() wakeup logic

1 files changed, 128 insertions, 156 deletions

diff --git a/erts/emulator/sys/common/erl_poll.c b/erts/emulator/sys/common/erl_poll.c
index 4d0ca97889..77ac2de5f6 100644
--- a/erts/emulator/sys/common/erl_poll.c
+++ b/erts/emulator/sys/common/erl_poll.c
@@ -1,7 +1,7 @@
 /*
  * %CopyrightBegin%
  *
- * Copyright Ericsson AB 2006-2010. All Rights Reserved.
+ * Copyright Ericsson AB 2006-2011. All Rights Reserved.
  *
  * The contents of this file are subject to the Erlang Public License,
  * Version 1.1, (the "License"); you may not use this file except in
@@ -124,25 +124,11 @@
   erts_smp_mtx_unlock(&(PS)->mtx)
 
 #define ERTS_POLLSET_SET_POLLED_CHK(PS) \
-  ((int) erts_smp_atomic_xchg(&(PS)->polled, (erts_aint_t) 1))
+  ((int) erts_atomic32_xchg(&(PS)->polled, (erts_aint32_t) 1))
 #define ERTS_POLLSET_UNSET_POLLED(PS) \
-  erts_smp_atomic_set(&(PS)->polled, (erts_aint_t) 0)
+  erts_atomic32_set(&(PS)->polled, (erts_aint32_t) 0)
 #define ERTS_POLLSET_IS_POLLED(PS) \
-  ((int) erts_smp_atomic_read(&(PS)->polled))
-
-#define ERTS_POLLSET_SET_POLLER_WOKEN_CHK(PS) set_poller_woken_chk((PS))
-#define ERTS_POLLSET_SET_POLLER_WOKEN(PS) 				\
-do {									\
-      ERTS_THR_MEMORY_BARRIER;						\
-      erts_smp_atomic_set(&(PS)->woken, (erts_aint_t) 1);		\
-} while (0)
-#define ERTS_POLLSET_UNSET_POLLER_WOKEN(PS)				\
-do {									\
-    erts_smp_atomic_set(&(PS)->woken, (erts_aint_t) 0);			\
-    ERTS_THR_MEMORY_BARRIER;						\
-} while (0)
-#define ERTS_POLLSET_IS_POLLER_WOKEN(PS)				\
-  ((int) erts_smp_atomic_read(&(PS)->woken))
+  ((int) erts_atomic32_read(&(PS)->polled))
 
 #else
 
@@ -152,69 +138,21 @@ do {									\
 #define ERTS_POLLSET_UNSET_POLLED(PS)
 #define ERTS_POLLSET_IS_POLLED(PS) 0
 
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
-
-/*
- * Ideally, the ERTS_POLLSET_SET_POLLER_WOKEN_CHK(PS) operation would
- * be atomic. This operation isn't, but we will do okay anyway. The
- * "woken check" is only an optimization. The only requirement we have:
- * If (PS)->woken is set to a value != 0 when interrupting, we have to
- * write on the the wakeup pipe at least once. Multiple writes are okay.
- */
-#define ERTS_POLLSET_SET_POLLER_WOKEN_CHK(PS) ((PS)->woken++)
-#define ERTS_POLLSET_SET_POLLER_WOKEN(PS) ((PS)->woken = 1, (void) 0)
-#define ERTS_POLLSET_UNSET_POLLER_WOKEN(PS) ((PS)->woken = 0, (void) 0)
-#define ERTS_POLLSET_IS_POLLER_WOKEN(PS) ((PS)->woken)
-
-#else
-
-#define ERTS_POLLSET_SET_POLLER_WOKEN_CHK(PS) 1
-#define ERTS_POLLSET_SET_POLLER_WOKEN(PS)
-#define ERTS_POLLSET_UNSET_POLLER_WOKEN(PS)
-#define ERTS_POLLSET_IS_POLLER_WOKEN(PS) 1
-
-#endif
-
 #endif
 
 #if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
 #define ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(PS) \
-  erts_smp_atomic_set(&(PS)->have_update_requests, (erts_aint_t) 1)
+  erts_smp_atomic32_set(&(PS)->have_update_requests, (erts_aint32_t) 1)
 #define ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(PS) \
-  erts_smp_atomic_set(&(PS)->have_update_requests, (erts_aint_t) 0)
+  erts_smp_atomic32_set(&(PS)->have_update_requests, (erts_aint32_t) 0)
 #define ERTS_POLLSET_HAVE_UPDATE_REQUESTS(PS) \
-  ((int) erts_smp_atomic_read(&(PS)->have_update_requests))
+  ((int) erts_smp_atomic32_read(&(PS)->have_update_requests))
 #else
 #define ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(PS)
 #define ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(PS)
 #define ERTS_POLLSET_HAVE_UPDATE_REQUESTS(PS) 0
 #endif
 
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT && !defined(ERTS_SMP)
-
-#define ERTS_POLLSET_UNSET_INTERRUPTED_CHK(PS) unset_interrupted_chk((PS))
-#define ERTS_POLLSET_UNSET_INTERRUPTED(PS) ((PS)->interrupt = 0, (void) 0)
-#define ERTS_POLLSET_SET_INTERRUPTED(PS) ((PS)->interrupt = 1, (void) 0)
-#define ERTS_POLLSET_IS_INTERRUPTED(PS) ((PS)->interrupt)
-
-#else
-
-#define ERTS_POLLSET_UNSET_INTERRUPTED_CHK(PS) unset_interrupted_chk((PS))
-#define ERTS_POLLSET_UNSET_INTERRUPTED(PS)				\
-do {									\
-    erts_smp_atomic_set(&(PS)->interrupt, (erts_aint_t) 0);		\
-    ERTS_THR_MEMORY_BARRIER;						\
-} while (0)
-#define ERTS_POLLSET_SET_INTERRUPTED(PS) 				\
-do {									\
-      ERTS_THR_MEMORY_BARRIER;						\
-      erts_smp_atomic_set(&(PS)->interrupt, (erts_aint_t) 1);		\
-} while (0)
-#define ERTS_POLLSET_IS_INTERRUPTED(PS)					\
-  ((int) erts_smp_atomic_read(&(PS)->interrupt))
-
-#endif
-
 #if ERTS_POLL_USE_FALLBACK
 #  if ERTS_POLL_USE_POLL
 #    define ERTS_POLL_NEED_FALLBACK(PS) ((PS)->no_poll_fds > 1)
@@ -318,14 +256,12 @@ struct ErtsPollSet_ {
 #if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
     ErtsPollSetUpdateRequestsBlock update_requests;
     ErtsPollSetUpdateRequestsBlock *curr_upd_req_block;
-    erts_smp_atomic_t have_update_requests;
+    erts_smp_atomic32_t have_update_requests;
 #endif
 #ifdef ERTS_SMP
-    erts_smp_atomic_t polled;
-    erts_smp_atomic_t woken;
+    erts_atomic32_t polled;
     erts_smp_mtx_t mtx;
 #elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
-    volatile int woken;
 #endif
 #if ERTS_POLL_USE_WAKEUP_PIPE
     int wake_fds[2];
@@ -333,12 +269,12 @@ struct ErtsPollSet_ {
 #if ERTS_POLL_USE_FALLBACK
     int fallback_used;
 #endif
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT && !defined(ERTS_SMP)
-    volatile int interrupt;
-#else
-    erts_smp_atomic_t interrupt;
+#ifdef ERTS_SMP
+    erts_atomic32_t wakeup_state;
+#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
+    volatile int wakeup_state;
 #endif
-    erts_smp_atomic_t timeout;
+    erts_smp_atomic32_t timeout;
 #ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
     erts_smp_atomic_t no_avoided_wakeups;
     erts_smp_atomic_t no_avoided_interrupts;
@@ -346,34 +282,6 @@ struct ErtsPollSet_ {
 #endif
 };
 
-static ERTS_INLINE int
-unset_interrupted_chk(ErtsPollSet ps)
-{
-    int res;
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT && !defined(ERTS_SMP)
-    /* This operation isn't atomic, but we have no need at all for an
-       atomic operation here... */
-    res = ps->interrupt;
-    ps->interrupt = 0;
-#else
-    res = (int) erts_smp_atomic_xchg(&ps->interrupt, (erts_aint_t) 0);
-    ERTS_THR_MEMORY_BARRIER;
-#endif
-    return res;
-
-}
-
-#ifdef ERTS_SMP
-
-static ERTS_INLINE int
-set_poller_woken_chk(ErtsPollSet ps)
-{
-    ERTS_THR_MEMORY_BARRIER;
-    return (int) erts_smp_atomic_xchg(&ps->woken, (erts_aint_t) 1);
-}
-
-#endif
-
 void erts_silence_warn_unused_result(long unused);
 static void fatal_error(char *format, ...);
 static void fatal_error_async_signal_safe(char *error_str);
@@ -430,6 +338,63 @@ static void check_poll_status(ErtsPollSet ps);
 static void print_misc_debug_info(void);
 #endif
 
+#define ERTS_POLL_NOT_WOKEN	0
+#define ERTS_POLL_WOKEN		-1
+#define ERTS_POLL_WOKEN_INTR	1
+
+static ERTS_INLINE void
+reset_wakeup_state(ErtsPollSet ps)
+{
+#ifdef ERTS_SMP
+    erts_atomic32_set(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN);
+#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
+    ps->wakeup_state = 0;
+#endif
+}
+
+static ERTS_INLINE int
+is_woken(ErtsPollSet ps)
+{
+#ifdef ERTS_SMP
+    return erts_atomic32_read_acqb(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN;
+#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
+    return ps->wakeup_state != ERTS_POLL_NOT_WOKEN;
+#else
+    return 0;
+#endif
+}
+
+static ERTS_INLINE int
+is_interrupted_reset(ErtsPollSet ps)
+{
+#ifdef ERTS_SMP
+    return (erts_atomic32_xchg(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN)
+	    == ERTS_POLL_WOKEN_INTR);
+#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
+    int res = ps->wakeup_state == ERTS_POLL_WOKEN_INTR;
+    ps->wakeup_state = ERTS_POLL_NOT_WOKEN;
+    return res;
+#else
+    return 0;
+#endif
+}
+
+static ERTS_INLINE void
+woke_up(ErtsPollSet ps)
+{
+#ifdef ERTS_SMP
+    erts_aint32_t wakeup_state = erts_atomic32_read(&ps->wakeup_state);
+    if (wakeup_state == ERTS_POLL_NOT_WOKEN)
+	(void) erts_atomic32_cmpxchg(&ps->wakeup_state,
+				     ERTS_POLL_WOKEN,
+				     ERTS_POLL_NOT_WOKEN);
+    ASSERT(erts_atomic32_read(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN);
+#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
+    if (ps->wakeup_state == ERTS_POLL_NOT_WOKEN)
+	ps->wakeup_state = ERTS_POLL_WOKEN;
+#endif
+}
+
 /*
  * --- Wakeup pipe -----------------------------------------------------------
  */
@@ -437,14 +402,34 @@ static void print_misc_debug_info(void);
 #if ERTS_POLL_USE_WAKEUP_PIPE
 
 static ERTS_INLINE void
-wake_poller(ErtsPollSet ps)
+wake_poller(ErtsPollSet ps, int interrupted)
 {
+    int wake;
+#ifdef ERTS_SMP
+    erts_aint32_t wakeup_state;
+    if (!interrupted)
+	wakeup_state = erts_atomic32_cmpxchg_relb(&ps->wakeup_state,
+						  ERTS_POLL_WOKEN,
+						  ERTS_POLL_NOT_WOKEN);
+    else {
+	/*
+	 * We might unnecessarily write to the pipe, however,
+	 * that isn't problematic.
+	 */
+	wakeup_state = erts_atomic32_read(&ps->wakeup_state);
+	erts_atomic32_set_relb(&ps->wakeup_state, ERTS_POLL_WOKEN_INTR);
+    }
+    wake = wakeup_state == ERTS_POLL_NOT_WOKEN;
+#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
+    wake = ps->wakeup_state == ERTS_POLL_NOT_WOKEN;
+    ps->wakeup_state = interrupted ? ERTS_POLL_WOKEN_INTR : ERTS_POLL_NOT_WOKEN;
+#endif
     /*
      * NOTE: This function might be called from signal handlers in the
      *       non-smp case; therefore, it has to be async-signal safe in
      *       the non-smp case.
      */
-    if (!ERTS_POLLSET_SET_POLLER_WOKEN_CHK(ps)) {
+    if (wake) {
 	ssize_t res;
 	if (ps->wake_fds[1] < 0)
 	    return; /* Not initialized yet */
@@ -1387,9 +1372,7 @@ handle_update_requests(ErtsPollSet ps)
 #endif /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */
 
 static ERTS_INLINE ErtsPollEvents
-poll_control(ErtsPollSet ps, int fd, ErtsPollEvents events, int on,
-	     int *have_set_have_update_requests,
-	     int *do_wake)
+poll_control(ErtsPollSet ps, int fd, ErtsPollEvents events, int on, int *do_wake)
 {
     ErtsPollEvents new_events;
 
@@ -1493,7 +1476,6 @@ ERTS_POLL_EXPORT(erts_poll_controlv)(ErtsPollSet ps,
 				     int len)
 {
     int i;
-    int hshur = 0;
     int do_wake;
     int final_do_wake = 0;
 
@@ -1505,17 +1487,17 @@ ERTS_POLL_EXPORT(erts_poll_controlv)(ErtsPollSet ps,
 				      pcev[i].fd,
 				      pcev[i].events,
 				      pcev[i].on,
-				      &hshur,
 				      &do_wake);
 	final_do_wake |= do_wake;
     }
 
+    ERTS_POLLSET_UNLOCK(ps);
+
 #ifdef ERTS_SMP
     if (final_do_wake)
-	wake_poller(ps);
+	wake_poller(ps, 0);
 #endif /* ERTS_SMP */
 
-    ERTS_POLLSET_UNLOCK(ps);
 }
 
 ErtsPollEvents
@@ -1526,20 +1508,20 @@ ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet ps,
 				    int* do_wake) /* In: Wake up polling thread */
 				                  /* Out: Poller is woken */
 {
-    int hshur = 0;
     ErtsPollEvents res;
 
     ERTS_POLLSET_LOCK(ps);
 
-    res = poll_control(ps, fd, events, on, &hshur, do_wake);
+    res = poll_control(ps, fd, events, on, do_wake);
+
+    ERTS_POLLSET_UNLOCK(ps);
 
 #ifdef ERTS_SMP
     if (*do_wake) {
-	wake_poller(ps);
+	wake_poller(ps, 0);
     }
 #endif /* ERTS_SMP */
 
-    ERTS_POLLSET_UNLOCK(ps);
     return res;
 }
 
@@ -1918,9 +1900,11 @@ check_fd_events(ErtsPollSet ps, SysTimeval *tv, int max_res, int *ps_locked)
 	return 0;
     }
     else {
-	erts_aint_t timeout = tv->tv_sec*1000 + tv->tv_usec/1000;
+	long timeout = tv->tv_sec*1000 + tv->tv_usec/1000;
+	if (timeout > ERTS_AINT32_T_MAX)
+	    timeout = ERTS_AINT32_T_MAX;
 	ASSERT(timeout >= 0);
-	erts_smp_atomic_set(&ps->timeout, timeout);
+	erts_smp_atomic32_set_relb(&ps->timeout, (erts_aint32_t) timeout);
 #if ERTS_POLL_USE_FALLBACK
 	if (!(ps->fallback_used = ERTS_POLL_NEED_FALLBACK(ps))) {
 
@@ -2042,15 +2026,14 @@ ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
 		 (int) tv->tv_sec*1000 + tv->tv_usec/1000);
 #endif
 
-    ERTS_POLLSET_UNSET_POLLER_WOKEN(ps);
     if (ERTS_POLLSET_SET_POLLED_CHK(ps)) {
 	res = EINVAL; /* Another thread is in erts_poll_wait()
 			 on this pollset... */
 	goto done;
     }
 
-    if (ERTS_POLLSET_IS_INTERRUPTED(ps)) {
-	/* Interrupt use zero timeout */
+    if (is_woken(ps)) {
+	/* Use zero timeout */
 	itv.tv_sec = 0;
 	itv.tv_usec = 0;
 	tvp = &itv;
@@ -2067,7 +2050,7 @@ ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
     ps_locked = 0;
     res = check_fd_events(ps, tvp, no_fds, &ps_locked);
 
-    ERTS_POLLSET_SET_POLLER_WOKEN(ps);
+    woke_up(ps);
 
     if (res == 0) {
 	res = ETIMEDOUT;
@@ -2099,9 +2082,7 @@ ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
 	check_poll_result(pr, no_fds);
 #endif
 
-	res = (no_fds == 0
-	       ? (ERTS_POLLSET_UNSET_INTERRUPTED_CHK(ps) ? EINTR : EAGAIN)
-	       : 0);
+	res = (no_fds == 0 ? (is_interrupted_reset(ps) ? EINTR : EAGAIN) : 0);
 	*len = no_fds;
     }
 
@@ -2112,7 +2093,7 @@ ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
 #endif
 
  done:
-    erts_smp_atomic_set(&ps->timeout, ERTS_AINT_T_MAX);
+    erts_smp_atomic32_set_relb(&ps->timeout, ERTS_AINT32_T_MAX);
 #ifdef ERTS_POLL_DEBUG_PRINT
     erts_printf("Leaving %s = erts_poll_wait()\n",
 		 res == 0 ? "0" : erl_errno_id(res));
@@ -2128,20 +2109,17 @@ ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
 void
 ERTS_POLL_EXPORT(erts_poll_interrupt)(ErtsPollSet ps, int set)
 {
+#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(ERTS_SMP)
     /*
      * NOTE: This function might be called from signal handlers in the
      *       non-smp case; therefore, it has to be async-signal safe in
      *       the non-smp case.
      */
-    if (set) {
-	ERTS_POLLSET_SET_INTERRUPTED(ps);
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(ERTS_SMP)
-	wake_poller(ps);
+    if (!set)
+	reset_wakeup_state(ps);
+    else
+	wake_poller(ps, 1);
 #endif
-    }
-    else {
-	ERTS_POLLSET_UNSET_INTERRUPTED(ps);
-    }
 }
 
 /*
@@ -2154,13 +2132,12 @@ ERTS_POLL_EXPORT(erts_poll_interrupt_timed)(ErtsPollSet ps,
 					    int set,
 					    long msec)
 {
-    if (set) {
-	if (erts_smp_atomic_read(&ps->timeout) > (erts_aint_t) msec) {
-	    ERTS_POLLSET_SET_INTERRUPTED(ps);
 #if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(ERTS_SMP)
-	    wake_poller(ps);
-#endif
-	}
+    if (!set)
+	reset_wakeup_state(ps);
+    else {
+	if (erts_smp_atomic32_read_acqb(&ps->timeout) > (erts_aint32_t) msec)
+	    wake_poller(ps, 1);
 #ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
 	else {
 	    if (ERTS_POLLSET_IS_POLLED(ps))
@@ -2170,9 +2147,7 @@ ERTS_POLL_EXPORT(erts_poll_interrupt_timed)(ErtsPollSet ps,
 	erts_smp_atomic_inc(&ps->no_interrupt_timed);
 #endif
     }
-    else {
-	ERTS_POLLSET_UNSET_INTERRUPTED(ps);
-    }
+#endif
 }
 
 int
@@ -2283,14 +2258,16 @@ ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
     ps->update_requests.next = NULL;
     ps->update_requests.len = 0;
     ps->curr_upd_req_block = &ps->update_requests;
-    erts_smp_atomic_init(&ps->have_update_requests, 0);
+    erts_smp_atomic32_init(&ps->have_update_requests, 0);
 #endif
 #ifdef ERTS_SMP
-    erts_smp_atomic_init(&ps->polled, 0);
-    erts_smp_atomic_init(&ps->woken, 0);
+    erts_atomic32_init(&ps->polled, 0);
     erts_smp_mtx_init(&ps->mtx, "pollset");
+#endif
+#ifdef ERTS_SMP
+    erts_atomic32_init(&ps->wakeup_state, (erts_aint32_t) 0);
 #elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
-    ps->woken = 0;
+    ps->wakeup_state = 0;
 #endif
 #if ERTS_POLL_USE_WAKEUP_PIPE
     create_wakeup_pipe(ps);
@@ -2312,12 +2289,7 @@ ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
 	ps->internal_fd_limit = kp_fd + 1;
     ps->kp_fd = kp_fd;
 #endif
-#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT && !defined(ERTS_SMP)
-    ps->interrupt = 0;
-#else
-    erts_smp_atomic_init(&ps->interrupt, 0);
-#endif
-    erts_smp_atomic_init(&ps->timeout, ERTS_AINT_T_MAX);
+    erts_smp_atomic32_init(&ps->timeout, ERTS_AINT32_T_MAX);
 #ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
     erts_smp_atomic_init(&ps->no_avoided_wakeups, 0);
     erts_smp_atomic_init(&ps->no_avoided_interrupts, 0);