# HG changeset patch
# User Valentin Bartenev <vbart@nginx.com>
# Date 1468585137 -10800
# Node ID 6acaa638fa074dada02ad4544a299584da9abc85
# Parent  18f6120e3b7a910c7b71c3a7185895153381269c
Events: support for EPOLLEXCLUSIVE.

This flag appeared in Linux 4.5 and is useful for avoiding thundering herd
problem.

The current Linux kernel implementation walks the list of exclusive waiters,
and queues an event to each epfd, until it finds the first waiter that has
threads blocked on it via epoll_wait().

diff --git a/auto/modules b/auto/modules
--- a/auto/modules
+++ b/auto/modules
@@ -43,6 +43,7 @@ fi
 if [ $NGX_TEST_BUILD_EPOLL = YES ]; then
     have=NGX_HAVE_EPOLL . auto/have
     have=NGX_HAVE_EPOLLRDHUP . auto/have
+    have=NGX_HAVE_EPOLLEXCLUSIVE . auto/have
     have=NGX_HAVE_EVENTFD . auto/have
     have=NGX_TEST_BUILD_EPOLL . auto/have
     EVENT_MODULES="$EVENT_MODULES $EPOLL_MODULE"
diff --git a/auto/os/linux b/auto/os/linux
--- a/auto/os/linux
+++ b/auto/os/linux
@@ -70,6 +70,22 @@ if [ $ngx_found = yes ]; then
                       ee.data.ptr = NULL;
                       epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ee)"
     . auto/feature
+
+
+    # EPOLLEXCLUSIVE appeared in Linux 4.5, glibc 2.24
+
+    ngx_feature="EPOLLEXCLUSIVE"
+    ngx_feature_name="NGX_HAVE_EPOLLEXCLUSIVE"
+    ngx_feature_run=no
+    ngx_feature_incs="#include <sys/epoll.h>"
+    ngx_feature_path=
+    ngx_feature_libs=
+    ngx_feature_test="int efd = 0, fd = 0;
+                      struct epoll_event ee;
+                      ee.events = EPOLLIN|EPOLLEXCLUSIVE;
+                      ee.data.ptr = NULL;
+                      epoll_ctl(efd, EPOLL_CTL_ADD, fd, &ee)"
+    . auto/feature
 fi
 
 
diff --git a/src/event/modules/ngx_epoll_module.c b/src/event/modules/ngx_epoll_module.c
--- a/src/event/modules/ngx_epoll_module.c
+++ b/src/event/modules/ngx_epoll_module.c
@@ -27,6 +27,7 @@
 
 #define EPOLLRDHUP     0x2000
 
+#define EPOLLEXCLUSIVE 0x10000000
 #define EPOLLONESHOT   0x40000000
 #define EPOLLET        0x80000000
 
@@ -610,6 +611,12 @@ ngx_epoll_add_event(ngx_event_t *ev, ngx
         op = EPOLL_CTL_ADD;
     }
 
+#if (NGX_HAVE_EPOLLEXCLUSIVE && NGX_HAVE_EPOLLRDHUP)
+    if (flags & NGX_EXCLUSIVE_EVENT) {
+        events &= ~EPOLLRDHUP;
+    }
+#endif
+
     ee.events = events | (uint32_t) flags;
     ee.data.ptr = (void *) ((uintptr_t) c | ev->instance);
 
diff --git a/src/event/ngx_event.c b/src/event/ngx_event.c
--- a/src/event/ngx_event.c
+++ b/src/event/ngx_event.c
@@ -822,15 +822,38 @@ ngx_event_process_init(ngx_cycle_t *cycl
         rev->handler = (c->type == SOCK_STREAM) ? ngx_event_accept
                                                 : ngx_event_recvmsg;
 
-        if (ngx_use_accept_mutex
 #if (NGX_HAVE_REUSEPORT)
-            && !ls[i].reuseport
+
+        if (ls[i].reuseport) {
+            if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
+                return NGX_ERROR;
+            }
+
+            continue;
+        }
+
 #endif
-           )
-        {
+
+        if (ngx_use_accept_mutex) {
             continue;
         }
 
+#if (NGX_HAVE_EPOLLEXCLUSIVE)
+
+        if ((ngx_event_flags & NGX_USE_EPOLL_EVENT)
+            && ccf->worker_processes > 1)
+        {
+            if (ngx_add_event(rev, NGX_READ_EVENT, NGX_EXCLUSIVE_EVENT)
+                == NGX_ERROR)
+            {
+                return NGX_ERROR;
+            }
+
+            continue;
+        }
+
+#endif
+
         if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
             return NGX_ERROR;
         }
diff --git a/src/event/ngx_event.h b/src/event/ngx_event.h
--- a/src/event/ngx_event.h
+++ b/src/event/ngx_event.h
@@ -367,6 +367,9 @@ extern ngx_uint_t            ngx_use_epo
 #define NGX_ONESHOT_EVENT  EPOLLONESHOT
 #endif
 
+#if (NGX_HAVE_EPOLLEXCLUSIVE)
+#define NGX_EXCLUSIVE_EVENT  EPOLLEXCLUSIVE
+#endif
 
 #elif (NGX_HAVE_POLL)
 
@@ -395,6 +398,11 @@ extern ngx_uint_t            ngx_use_epo
 #endif
 
 
+#if (NGX_TEST_BUILD_EPOLL)
+#define NGX_EXCLUSIVE_EVENT  0
+#endif
+
+
 #ifndef NGX_CLEAR_EVENT
 #define NGX_CLEAR_EVENT    0    /* dummy declaration */
 #endif