When the other end of a chardev connection isn't picking up data as
fast as we're sending, we just used to keep spinning in a tight loop
till all the data was sent out.
Polling for POLLOUT indefinitely gives the other end a chance to catch
up and also saves us CPU cycles.
Signed-off-by: Amit Shah <amit.s...@redhat.com>
---
qemu-char.c | 17 +++++++++++++++--
1 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/qemu-char.c b/qemu-char.c
index d5b1662..48e1e57 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -36,6 +36,7 @@
#include <unistd.h>
#include <fcntl.h>
+#include <poll.h>
#include <signal.h>
#include <time.h>
#include <errno.h>
@@ -513,15 +514,27 @@ int send_all(int fd, const void *buf, size_t *len)
static int unix_write(int fd, const uint8_t *buf, size_t *len)
{
+ struct pollfd pollfds[1];
ssize_t tmplen, ret;
+ pollfds[0].fd = fd;
+ pollfds[0].events = POLLOUT;
+
tmplen = *len;
*len = 0;
while (tmplen > 0) {
+ ret = poll(pollfds, 1, -1);
+ if (ret == -1) {
+ if (errno == EINTR) {
+ continue;
+ }
+ return -1;
+ }
ret = write(fd, buf, tmplen);
if (ret < 0) {
- if (errno != EINTR && errno != EAGAIN)
- return -1;
+ if (errno != EINTR && errno != EAGAIN) {
+ return -1;
+ }
} else if (ret == 0) {
break;
} else {
--
1.6.2.5
