block: make raw aio signaling non-blocking (Gerd Hoffman)

This patch switches the read handle of the signaling pipe into
non-blocking mode.  This avoids unwanted blocking reads and also
allows to read all bytes out of the signaling pipe in case we got
signaled more that once before the handler ran.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5716 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 10 insertions, 7 deletions

diff --git a/block-raw-posix.c b/block-raw-posix.c
index c06e38d..0a06a12 100644
--- a/block-raw-posix.c
+++ b/block-raw-posix.c
@@ -497,15 +497,17 @@ static void posix_aio_read(void *opaque)
     int ret;
     ssize_t len;
 
-    do {
-        char byte;
+    /* read all bytes from signal pipe */
+    for (;;) {
+        char bytes[16];
 
-        len = read(s->rfd, &byte, 1);
+        len = read(s->rfd, bytes, sizeof(bytes));
         if (len == -1 && errno == EINTR)
-            continue;
-        if (len == -1 && errno == EAGAIN)
-            break;
-    } while (len == -1);
+            continue; /* try again */
+        if (len == sizeof(bytes))
+            continue; /* more to read */
+        break;
+    }
 
     for(;;) {
         pacb = &s->first_aio;
@@ -591,6 +593,7 @@ static int posix_aio_init(void)
     s->rfd = fds[0];
     s->wfd = fds[1];
 
+    fcntl(s->rfd, F_SETFL, O_NONBLOCK);
     fcntl(s->wfd, F_SETFL, O_NONBLOCK);
 
     qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush, s);