* [PATCH v3 1/2] Revert "vsock: Fix blocking ops call in prepare_to_wait"
2016-03-22 16:05 [PATCH v3 0/2] AF_VSOCK: Shrink the area influenced by prepare_to_wait Claudio Imbrenda
@ 2016-03-22 16:05 ` Claudio Imbrenda
2016-03-22 16:05 ` [PATCH v3 2/2] AF_VSOCK: Shrink the area influenced by prepare_to_wait Claudio Imbrenda
2016-03-22 20:19 ` [PATCH v3 0/2] " David Miller
2 siblings, 0 replies; 4+ messages in thread
From: Claudio Imbrenda @ 2016-03-22 16:05 UTC (permalink / raw)
To: davem; +Cc: labbott, netdev, linux-kernel
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>
---
net/vmw_vsock/af_vsock.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
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 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
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 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
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 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
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 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
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 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
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 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
*/
err = -ENOMEM;
- goto out;
+ goto out_wait;
} else if (ready > 0) {
ssize_t read;
@@ -1746,7 +1750,7 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
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 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
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 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
err = -EAGAIN;
break;
}
+
+ prepare_to_wait(sk_sleep(sk), &wait,
+ TASK_INTERRUPTIBLE);
}
}
@@ -1811,6 +1816,8 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
err = copied;
}
+out_wait:
+ finish_wait(sk_sleep(sk), &wait);
out:
release_sock(sk);
return err;
--
1.9.1
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v3 2/2] AF_VSOCK: Shrink the area influenced by prepare_to_wait
2016-03-22 16:05 [PATCH v3 0/2] AF_VSOCK: Shrink the area influenced by prepare_to_wait Claudio Imbrenda
2016-03-22 16:05 ` [PATCH v3 1/2] Revert "vsock: Fix blocking ops call in prepare_to_wait" Claudio Imbrenda
@ 2016-03-22 16:05 ` Claudio Imbrenda
2016-03-22 20:19 ` [PATCH v3 0/2] " David Miller
2 siblings, 0 replies; 4+ messages in thread
From: Claudio Imbrenda @ 2016-03-22 16:05 UTC (permalink / raw)
To: davem; +Cc: labbott, netdev, linux-kernel
When a thread is prepared for waiting by calling prepare_to_wait, sleeping
is not allowed until either the wait has taken place or finish_wait has
been called. The existing code in af_vsock imposed unnecessary no-sleep
assumptions to a broad list of backend functions.
This patch shrinks the influence of prepare_to_wait to the area where it
is strictly needed, therefore relaxing the no-sleep restriction there.
Signed-off-by: Claudio Imbrenda <imbrenda@linux.vnet.ibm.com>
---
net/vmw_vsock/af_vsock.c | 158 +++++++++++++++++++++++++----------------------
1 file changed, 85 insertions(+), 73 deletions(-)
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 7fd1220..3dce53e 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1209,10 +1209,14 @@ static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr,
if (signal_pending(current)) {
err = sock_intr_errno(timeout);
- goto out_wait_error;
+ sk->sk_state = SS_UNCONNECTED;
+ sock->state = SS_UNCONNECTED;
+ goto out_wait;
} else if (timeout == 0) {
err = -ETIMEDOUT;
- goto out_wait_error;
+ sk->sk_state = SS_UNCONNECTED;
+ sock->state = SS_UNCONNECTED;
+ goto out_wait;
}
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
@@ -1220,20 +1224,17 @@ static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr,
if (sk->sk_err) {
err = -sk->sk_err;
- goto out_wait_error;
- } else
+ sk->sk_state = SS_UNCONNECTED;
+ sock->state = SS_UNCONNECTED;
+ } else {
err = 0;
+ }
out_wait:
finish_wait(sk_sleep(sk), &wait);
out:
release_sock(sk);
return err;
-
-out_wait_error:
- sk->sk_state = SS_UNCONNECTED;
- sock->state = SS_UNCONNECTED;
- goto out_wait;
}
static int vsock_accept(struct socket *sock, struct socket *newsock, int flags)
@@ -1270,18 +1271,20 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, int flags)
listener->sk_err == 0) {
release_sock(listener);
timeout = schedule_timeout(timeout);
+ finish_wait(sk_sleep(listener), &wait);
lock_sock(listener);
if (signal_pending(current)) {
err = sock_intr_errno(timeout);
- goto out_wait;
+ goto out;
} else if (timeout == 0) {
err = -EAGAIN;
- goto out_wait;
+ goto out;
}
prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE);
}
+ finish_wait(sk_sleep(listener), &wait);
if (listener->sk_err)
err = -listener->sk_err;
@@ -1301,19 +1304,15 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, int flags)
*/
if (err) {
vconnected->rejected = true;
- release_sock(connected);
- sock_put(connected);
- goto out_wait;
+ } else {
+ newsock->state = SS_CONNECTED;
+ sock_graft(connected, newsock);
}
- newsock->state = SS_CONNECTED;
- sock_graft(connected, newsock);
release_sock(connected);
sock_put(connected);
}
-out_wait:
- finish_wait(sk_sleep(listener), &wait);
out:
release_sock(listener);
return err;
@@ -1557,11 +1556,11 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
if (err < 0)
goto out;
- prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
while (total_written < len) {
ssize_t written;
+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
while (vsock_stream_has_space(vsk) == 0 &&
sk->sk_err == 0 &&
!(sk->sk_shutdown & SEND_SHUTDOWN) &&
@@ -1570,27 +1569,33 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
/* Don't wait for non-blocking sockets. */
if (timeout == 0) {
err = -EAGAIN;
- goto out_wait;
+ finish_wait(sk_sleep(sk), &wait);
+ goto out_err;
}
err = transport->notify_send_pre_block(vsk, &send_data);
- if (err < 0)
- goto out_wait;
+ if (err < 0) {
+ finish_wait(sk_sleep(sk), &wait);
+ goto out_err;
+ }
release_sock(sk);
timeout = schedule_timeout(timeout);
lock_sock(sk);
if (signal_pending(current)) {
err = sock_intr_errno(timeout);
- goto out_wait;
+ finish_wait(sk_sleep(sk), &wait);
+ goto out_err;
} else if (timeout == 0) {
err = -EAGAIN;
- goto out_wait;
+ finish_wait(sk_sleep(sk), &wait);
+ goto out_err;
}
prepare_to_wait(sk_sleep(sk), &wait,
TASK_INTERRUPTIBLE);
}
+ finish_wait(sk_sleep(sk), &wait);
/* These checks occur both as part of and after the loop
* conditional since we need to check before and after
@@ -1598,16 +1603,16 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
*/
if (sk->sk_err) {
err = -sk->sk_err;
- goto out_wait;
+ goto out_err;
} else if ((sk->sk_shutdown & SEND_SHUTDOWN) ||
(vsk->peer_shutdown & RCV_SHUTDOWN)) {
err = -EPIPE;
- goto out_wait;
+ goto out_err;
}
err = transport->notify_send_pre_enqueue(vsk, &send_data);
if (err < 0)
- goto out_wait;
+ goto out_err;
/* Note that enqueue will only write as many bytes as are free
* in the produce queue, so we don't need to ensure len is
@@ -1620,7 +1625,7 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
len - total_written);
if (written < 0) {
err = -ENOMEM;
- goto out_wait;
+ goto out_err;
}
total_written += written;
@@ -1628,14 +1633,13 @@ static int vsock_stream_sendmsg(struct socket *sock, struct msghdr *msg,
err = transport->notify_send_post_enqueue(
vsk, written, &send_data);
if (err < 0)
- goto out_wait;
+ goto out_err;
}
-out_wait:
+out_err:
if (total_written > 0)
err = total_written;
- finish_wait(sk_sleep(sk), &wait);
out:
release_sock(sk);
return err;
@@ -1716,21 +1720,61 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
if (err < 0)
goto out;
- prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
while (1) {
- s64 ready = vsock_stream_has_data(vsk);
+ s64 ready;
- if (ready < 0) {
- /* Invalid queue pair content. XXX This should be
- * changed to a connection reset in a later change.
- */
+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+ ready = vsock_stream_has_data(vsk);
- err = -ENOMEM;
- goto out_wait;
- } else if (ready > 0) {
+ if (ready == 0) {
+ if (sk->sk_err != 0 ||
+ (sk->sk_shutdown & RCV_SHUTDOWN) ||
+ (vsk->peer_shutdown & SEND_SHUTDOWN)) {
+ finish_wait(sk_sleep(sk), &wait);
+ break;
+ }
+ /* Don't wait for non-blocking sockets. */
+ if (timeout == 0) {
+ err = -EAGAIN;
+ finish_wait(sk_sleep(sk), &wait);
+ break;
+ }
+
+ err = transport->notify_recv_pre_block(
+ vsk, target, &recv_data);
+ if (err < 0) {
+ finish_wait(sk_sleep(sk), &wait);
+ break;
+ }
+ release_sock(sk);
+ timeout = schedule_timeout(timeout);
+ lock_sock(sk);
+
+ if (signal_pending(current)) {
+ err = sock_intr_errno(timeout);
+ finish_wait(sk_sleep(sk), &wait);
+ break;
+ } else if (timeout == 0) {
+ err = -EAGAIN;
+ finish_wait(sk_sleep(sk), &wait);
+ break;
+ }
+ } else {
ssize_t read;
+ finish_wait(sk_sleep(sk), &wait);
+
+ if (ready < 0) {
+ /* Invalid queue pair content. XXX This should
+ * be changed to a connection reset in a later
+ * change.
+ */
+
+ err = -ENOMEM;
+ goto out;
+ }
+
err = transport->notify_recv_pre_dequeue(
vsk, target, &recv_data);
if (err < 0)
@@ -1750,42 +1794,12 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
vsk, target, read,
!(flags & MSG_PEEK), &recv_data);
if (err < 0)
- goto out_wait;
+ goto out;
if (read >= target || flags & MSG_PEEK)
break;
target -= read;
- } else {
- if (sk->sk_err != 0 || (sk->sk_shutdown & RCV_SHUTDOWN)
- || (vsk->peer_shutdown & SEND_SHUTDOWN)) {
- break;
- }
- /* Don't wait for non-blocking sockets. */
- if (timeout == 0) {
- err = -EAGAIN;
- break;
- }
-
- err = transport->notify_recv_pre_block(
- vsk, target, &recv_data);
- if (err < 0)
- break;
-
- release_sock(sk);
- timeout = schedule_timeout(timeout);
- lock_sock(sk);
-
- if (signal_pending(current)) {
- err = sock_intr_errno(timeout);
- break;
- } else if (timeout == 0) {
- err = -EAGAIN;
- break;
- }
-
- prepare_to_wait(sk_sleep(sk), &wait,
- TASK_INTERRUPTIBLE);
}
}
@@ -1816,8 +1830,6 @@ vsock_stream_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
err = copied;
}
-out_wait:
- finish_wait(sk_sleep(sk), &wait);
out:
release_sock(sk);
return err;
--
1.9.1
^ permalink raw reply related [flat|nested] 4+ messages in thread