Revert "vsock: Fix blocking ops call in prepare_to_wait"
This reverts commit 5988818008257ca42010d6b43a3e0e48afec9898 ("vsock: Fix
blocking ops call in prepare_to_wait")
The commit reverted with this patch caused us to potentially miss wakeups.
Since the condition is not checked between the prepare_to_wait and the
schedule(), if a wakeup happens after the condition is checked but before
the sleep happens, we will miss it. ( A description of the problem can be
found here: http://www.makelinux.net/ldd3/chp-6-sect-2 ).
By reverting the patch, the behaviour is still incorrect (since we
shouldn't sleep between the prepare_to_wait and the schedule) but at least
it will not miss wakeups.
The next patch in the series actually fixes the behaviour.
Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index bbe65dc..7fd1220 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1557,6 +1557,8 @@
if (err < 0)
goto out;
+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+
while (total_written < len) {
ssize_t written;
@@ -1576,9 +1578,7 @@
goto out_wait;
release_sock(sk);
- prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
timeout = schedule_timeout(timeout);
- finish_wait(sk_sleep(sk), &wait);
lock_sock(sk);
if (signal_pending(current)) {
err = sock_intr_errno(timeout);
@@ -1588,6 +1588,8 @@
goto out_wait;
}
+ prepare_to_wait(sk_sleep(sk), &wait,
+ TASK_INTERRUPTIBLE);
}
/* These checks occur both as part of and after the loop
@@ -1633,6 +1635,7 @@
out_wait:
if (total_written > 0)
err = total_written;
+ finish_wait(sk_sleep(sk), &wait);
out:
release_sock(sk);
return err;
@@ -1713,6 +1716,7 @@
if (err < 0)
goto out;
+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
while (1) {
s64 ready = vsock_stream_has_data(vsk);
@@ -1723,7 +1727,7 @@
*/
err = -ENOMEM;
- goto out;
+ goto out_wait;
} else if (ready > 0) {
ssize_t read;
@@ -1746,7 +1750,7 @@
vsk, target, read,
!(flags & MSG_PEEK), &recv_data);
if (err < 0)
- goto out;
+ goto out_wait;
if (read >= target || flags & MSG_PEEK)
break;
@@ -1769,9 +1773,7 @@
break;
release_sock(sk);
- prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
timeout = schedule_timeout(timeout);
- finish_wait(sk_sleep(sk), &wait);
lock_sock(sk);
if (signal_pending(current)) {
@@ -1781,6 +1783,9 @@
err = -EAGAIN;
break;
}
+
+ prepare_to_wait(sk_sleep(sk), &wait,
+ TASK_INTERRUPTIBLE);
}
}
@@ -1811,6 +1816,8 @@
err = copied;
}
+out_wait:
+ finish_wait(sk_sleep(sk), &wait);
out:
release_sock(sk);
return err;