Merge pull request #279 from apple/mad/greedy-signalfd
Fix improper double-fire of signal sources on Linux
diff --git a/dispatch/once.h b/dispatch/once.h
index 68acfe8..37a4950 100644
--- a/dispatch/once.h
+++ b/dispatch/once.h
@@ -40,6 +40,14 @@
DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
typedef long dispatch_once_t;
+#if defined(__x86_64__) || defined(__i386__) || defined(__s390x__)
+#define DISPATCH_ONCE_INLINE_FASTPATH 1
+#elif defined(__APPLE__)
+#define DISPATCH_ONCE_INLINE_FASTPATH 1
+#else
+#define DISPATCH_ONCE_INLINE_FASTPATH 0
+#endif
+
/*!
* @function dispatch_once
*
@@ -65,6 +73,7 @@
dispatch_once(dispatch_once_t *predicate,
DISPATCH_NOESCAPE dispatch_block_t block);
+#if DISPATCH_ONCE_INLINE_FASTPATH
DISPATCH_INLINE DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL_ALL DISPATCH_NOTHROW
DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
void
@@ -81,6 +90,7 @@
#undef dispatch_once
#define dispatch_once _dispatch_once
#endif
+#endif // DISPATCH_ONCE_INLINE_FASTPATH
API_AVAILABLE(macos(10.6), ios(4.0))
DISPATCH_EXPORT DISPATCH_NONNULL1 DISPATCH_NONNULL3 DISPATCH_NOTHROW
@@ -89,6 +99,7 @@
dispatch_once_f(dispatch_once_t *predicate, void *_Nullable context,
dispatch_function_t function);
+#if DISPATCH_ONCE_INLINE_FASTPATH
DISPATCH_INLINE DISPATCH_ALWAYS_INLINE DISPATCH_NONNULL1 DISPATCH_NONNULL3
DISPATCH_NOTHROW
DISPATCH_SWIFT3_UNAVAILABLE("Use lazily initialized globals instead")
@@ -105,6 +116,7 @@
}
#undef dispatch_once_f
#define dispatch_once_f _dispatch_once_f
+#endif // DISPATCH_ONCE_INLINE_FASTPATH
__END_DECLS
diff --git a/src/event/event_epoll.c b/src/event/event_epoll.c
index dfdd00c..c86421b 100644
--- a/src/event/event_epoll.c
+++ b/src/event/event_epoll.c
@@ -51,7 +51,8 @@
int dmn_ident;
uint32_t dmn_events;
int16_t dmn_filter;
- bool dmn_socket_listener;
+ bool dmn_skip_outq_ioctl;
+ bool dmn_skip_inq_ioctl;
} *dispatch_muxnote_t;
typedef struct dispatch_epoll_timeout_s {
@@ -143,7 +144,7 @@
struct stat sb;
int fd = du._du->du_ident;
int16_t filter = du._du->du_filter;
- bool socket_listener = false;
+ bool skip_outq_ioctl = false, skip_inq_ioctl = false;
sigset_t sigmask;
switch (filter) {
@@ -173,11 +174,15 @@
if (fd < 0) {
return NULL;
}
+ // Linux doesn't support output queue size ioctls for regular files
+ skip_outq_ioctl = true;
} else if (S_ISSOCK(sb.st_mode)) {
socklen_t vlen = sizeof(int);
int v;
+ // Linux doesn't support saying how many clients are ready to be
+ // accept()ed for sockets
if (getsockopt(fd, SOL_SOCKET, SO_ACCEPTCONN, &v, &vlen) == 0) {
- socket_listener = (bool)v;
+ skip_inq_ioctl = (bool)v;
}
}
break;
@@ -193,7 +198,8 @@
dmn->dmn_ident = du._du->du_ident;
dmn->dmn_filter = filter;
dmn->dmn_events = events;
- dmn->dmn_socket_listener = socket_listener;
+ dmn->dmn_skip_outq_ioctl = skip_outq_ioctl;
+ dmn->dmn_skip_inq_ioctl = skip_inq_ioctl;
return dmn;
}
@@ -316,6 +322,7 @@
if (events == dmn->dmn_events) {
// nothing to do
} else if (events & (EPOLLIN | EPOLLOUT)) {
+ dmn->dmn_events = events;
_dispatch_epoll_update(dmn, EPOLL_CTL_MOD);
} else {
epoll_ctl(_dispatch_epfd, EPOLL_CTL_DEL, dmn->dmn_fd, NULL);
@@ -491,16 +498,28 @@
static uintptr_t
_dispatch_get_buffer_size(dispatch_muxnote_t dmn, bool writer)
{
- unsigned long op = writer ? SIOCOUTQ : SIOCINQ;
int n;
- if (!writer && dmn->dmn_socket_listener) {
- // Linux doesn't support saying how many clients are ready to be
- // accept()ed
+ if (writer ? dmn->dmn_skip_outq_ioctl : dmn->dmn_skip_inq_ioctl) {
return 1;
}
- if (dispatch_assume_zero(ioctl(dmn->dmn_ident, op, &n))) {
+ if (ioctl(dmn->dmn_ident, writer ? SIOCOUTQ : SIOCINQ, &n) != 0) {
+ switch (errno) {
+ case EINVAL:
+ case ENOTTY:
+ // this file descriptor actually doesn't support the buffer
+ // size ioctl, remember that for next time to avoid the syscall.
+ break;
+ default:
+ dispatch_assume_zero(errno);
+ break;
+ }
+ if (writer) {
+ dmn->dmn_skip_outq_ioctl = true;
+ } else {
+ dmn->dmn_skip_inq_ioctl = true;
+ }
return 1;
}
return (uintptr_t)n;
diff --git a/src/once.c b/src/once.c
index 75d7a39..c01538c 100644
--- a/src/once.c
+++ b/src/once.c
@@ -40,9 +40,15 @@
}
#endif
-DISPATCH_NOINLINE
-void
-dispatch_once_f(dispatch_once_t *val, void *ctxt, dispatch_function_t func)
+#if DISPATCH_ONCE_INLINE_FASTPATH
+#define DISPATCH_ONCE_SLOW_INLINE inline DISPATCH_ALWAYS_INLINE
+#else
+#define DISPATCH_ONCE_SLOW_INLINE DISPATCH_NOINLINE
+#endif // DISPATCH_ONCE_INLINE_FASTPATH
+
+DISPATCH_ONCE_SLOW_INLINE
+static void
+dispatch_once_f_slow(dispatch_once_t *val, void *ctxt, dispatch_function_t func)
{
#if DISPATCH_GATE_USE_FOR_DISPATCH_ONCE
dispatch_once_gate_t l = (dispatch_once_gate_t)val;
@@ -95,3 +101,15 @@
}
#endif
}
+
+DISPATCH_NOINLINE
+void
+dispatch_once_f(dispatch_once_t *val, void *ctxt, dispatch_function_t func)
+{
+#if !DISPATCH_ONCE_INLINE_FASTPATH
+ if (likely(os_atomic_load(val, acquire) == DLOCK_ONCE_DONE)) {
+ return;
+ }
+#endif // !DISPATCH_ONCE_INLINE_FASTPATH
+ return dispatch_once_f_slow(val, ctxt, func);
+}
diff --git a/src/shims/lock.h b/src/shims/lock.h
index 99c5563..0c089aa 100644
--- a/src/shims/lock.h
+++ b/src/shims/lock.h
@@ -59,9 +59,6 @@
#elif defined(__linux__)
#include <linux/futex.h>
-#if !defined(__x86_64__) && !defined(__i386__) && !defined(__s390x__)
-#include <linux/membarrier.h>
-#endif
#include <unistd.h>
#include <sys/syscall.h> /* For SYS_xxx definitions */
@@ -473,28 +470,7 @@
static inline dispatch_once_t
_dispatch_once_xchg_done(dispatch_once_t *pred)
{
-#if defined(__i386__) || defined(__x86_64__) || defined(__s390x__)
- // On Intel, any load is a load-acquire, so we don't need to be fancy
- // same for s390x
return os_atomic_xchg(pred, DLOCK_ONCE_DONE, release);
-#elif defined(__linux__)
- if (unlikely(syscall(__NR_membarrier, MEMBARRIER_CMD_SHARED, 0) < 0)) {
- /*
- * sys_membarrier not supported
- *
- * Ideally we would call DISPATCH_INTERNAL_CRASH() here, but
- * due to ordering constraints in internal.h required by Darwin
- * the macro is undefined when this header is included.
- * Instead, open-code what would be a call to
- * _dispatch_hardware_crash() inside DISPATCH_INTERNAL_CRASH().
- */
- __asm__("");
- __builtin_trap();
- }
- return os_atomic_xchg(pred, DLOCK_ONCE_DONE, relaxed);
-#else
-# error dispatch_once algorithm not available for this port
-#endif
}
DISPATCH_ALWAYS_INLINE
diff --git a/tests/dispatch_timer.c b/tests/dispatch_timer.c
index bebbc0d..e480ec2 100644
--- a/tests/dispatch_timer.c
+++ b/tests/dispatch_timer.c
@@ -86,7 +86,8 @@
fprintf(stderr, "%d\n", ++i);
if (i >= stop_at) {
test_long("i", i, stop_at);
- dispatch_source_set_timer(s, dispatch_time(DISPATCH_TIME_NOW, 0), 0, 0);
+ dispatch_source_set_timer(s, dispatch_time(DISPATCH_TIME_NOW, 0),
+ DISPATCH_TIME_FOREVER, 0);
dispatch_source_cancel(s);
}
});
