rbd-nbd: use EventSocket to notify terminate

instead of periodically checking a variable

Signed-off-by: Mykola Golub <mgolub@suse.com>

diff --git a/src/tools/rbd_nbd/rbd-nbd.cc b/src/tools/rbd_nbd/rbd-nbd.cc
index 80737de19b5b14c6f15ceb4f7717c887d20a3304..5494348bb50b5ded179346ce43a4a0c6aa908f02 100644 (file)
--- a/src/tools/rbd_nbd/rbd-nbd.cc
+++ b/src/tools/rbd_nbd/rbd-nbd.cc
@@ -62,6 +62,7 @@ namespace fs = std::experimental::filesystem;
 #include "common/config.h"
 #include "common/dout.h"
 #include "common/errno.h"
+#include "common/event_socket.h"
 #include "common/module.h"
 #include "common/safe_io.h"
 #include "common/version.h"
@@ -158,7 +159,7 @@ static void usage()
 
 static int nbd = -1;
 static int nbd_index = -1;
-static bool nbd_terminate = false;
+static EventSocket terminate_event_sock;
 
 #define RBD_NBD_BLKSIZE 512UL
 
@@ -218,6 +219,7 @@ public:
   }
 
 private:
+  int terminate_event_fd = -1;
   ceph::mutex disconnect_lock =
     ceph::make_mutex("NBDServer::DisconnectLocker");
   ceph::condition_variable disconnect_cond;
@@ -335,10 +337,12 @@ private:
 
   void reader_entry()
   {
-    struct pollfd poll_fds[1];
-    memset(poll_fds, 0, sizeof(struct pollfd));
+    struct pollfd poll_fds[2];
+    memset(poll_fds, 0, sizeof(struct pollfd) * 2);
     poll_fds[0].fd = fd;
     poll_fds[0].events = POLLIN;
+    poll_fds[1].fd = terminate_event_fd;
+    poll_fds[1].events = POLLIN;
 
     while (true) {
       std::unique_ptr<IOContext> ctx(new IOContext());
@@ -346,12 +350,7 @@ private:
 
       dout(20) << __func__ << ": waiting for nbd request" << dendl;
 
-      // We can not block on read because we have to check periodically
-      // nbd_terminate flag set by the signal handler.
-      // So to prevent blocking use poll with timeout to ensure we
-      // have some data comes before calling read.
-
-      int r = poll(poll_fds, 1, 1000);
+      int r = poll(poll_fds, 2, -1);
       if (r == -1) {
         if (errno == EINTR) {
           continue;
@@ -361,13 +360,13 @@ private:
         goto signal;
       }
 
-      if (nbd_terminate) {
-        dout(0) << "terminate received" << dendl;
+      if ((poll_fds[1].revents & POLLIN) != 0) {
+        dout(0) << __func__ << ": terminate received" << dendl;
         goto signal;
       }
 
       if ((poll_fds[0].revents & POLLIN) == 0) {
-        dout(20) << __func__ << ": poll timed out" << dendl;
+        dout(20) << __func__ << ": nothing to read" << dendl;
         continue;
       }
 
@@ -589,6 +588,12 @@ public:
 
       started = true;
 
+      terminate_event_fd = eventfd(0, EFD_NONBLOCK);
+      ceph_assert(terminate_event_fd > 0);
+      int r = terminate_event_sock.init(terminate_event_fd,
+                                        EVENT_SOCKET_TYPE_EVENTFD);
+      ceph_assert(r >= 0);
+
       reader_thread.create("rbd_reader");
       writer_thread.create("rbd_writer");
       if (cfg->quiesce) {
@@ -633,7 +638,8 @@ public:
     if (started) {
       dout(10) << __func__ << ": terminating" << dendl;
 
-      nbd_terminate = true;
+      terminate_event_sock.notify();
+
       reader_thread.join();
       writer_thread.join();
       if (cfg->quiesce) {
@@ -642,6 +648,7 @@ public:
 
       assert_clean();
 
+      close(terminate_event_fd);
       started = false;
     }
   }
@@ -1383,8 +1390,10 @@ static void handle_signal(int signum)
   ceph_assert(signum == SIGINT || signum == SIGTERM);
   derr << "*** Got signal " << sig_str(signum) << " ***" << dendl;
 
-  dout(20) << __func__ << ": " << "setting terminate flag" << dendl;
-  nbd_terminate = true;
+  dout(20) << __func__ << ": " << "notifying terminate" << dendl;
+
+  ceph_assert(terminate_event_sock.is_valid());
+  terminate_event_sock.notify();
 }
 
 static NBDServer *start_server(int fd, librbd::Image& image, Config *cfg)