nbd: take receive_mutex when reading requests[].receiving
requests[].receiving is set by nbd_receive_replies() under the receive_mutex;
Read it under the same mutex as well. Waking up receivers on errors happens
after each reply finishes processing, in nbd_co_receive_one_chunk().
If there is no currently-active reply, there are two cases:
* either there is no active request at all, in which case no
element of request[] can have .receiving = true
* or nbd_receive_replies() must be running and owns receive_mutex;
in that case it will get back to nbd_co_receive_one_chunk() because
the socket has been shutdown, and all waiting coroutines will wake up
in turn.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220414175756.671165-9-pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Reviewed-by: Lukas Straub <lukasstraub2@web.de>
Signed-off-by: Eric Blake <eblake@redhat.com>
diff --git a/block/nbd.c b/block/nbd.c
index a5c690c..3bfcf4d 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -131,6 +131,7 @@
s->x_dirty_bitmap = NULL;
}
+/* Called with s->receive_mutex taken. */
static bool coroutine_fn nbd_recv_coroutine_wake_one(NBDClientRequest *req)
{
if (req->receiving) {
@@ -142,12 +143,13 @@
return false;
}
-static void coroutine_fn nbd_recv_coroutines_wake(BDRVNBDState *s, bool all)
+static void coroutine_fn nbd_recv_coroutines_wake(BDRVNBDState *s)
{
int i;
+ QEMU_LOCK_GUARD(&s->receive_mutex);
for (i = 0; i < MAX_NBD_REQUESTS; i++) {
- if (nbd_recv_coroutine_wake_one(&s->requests[i]) && !all) {
+ if (nbd_recv_coroutine_wake_one(&s->requests[i])) {
return;
}
}
@@ -168,8 +170,6 @@
} else {
s->state = NBD_CLIENT_QUIT;
}
-
- nbd_recv_coroutines_wake(s, true);
}
static void coroutine_fn nbd_channel_error(BDRVNBDState *s, int ret)
@@ -432,11 +432,10 @@
qemu_coroutine_yield();
/*
- * We may be woken for 3 reasons:
+ * We may be woken for 2 reasons:
* 1. From this function, executing in parallel coroutine, when our
* handle is received.
- * 2. From nbd_channel_error(), when connection is lost.
- * 3. From nbd_co_receive_one_chunk(), when previous request is
+ * 2. From nbd_co_receive_one_chunk(), when previous request is
* finished and s->reply.handle set to 0.
* Anyway, it's OK to lock the mutex and go to the next iteration.
*/
@@ -928,7 +927,7 @@
}
s->reply.handle = 0;
- nbd_recv_coroutines_wake(s, false);
+ nbd_recv_coroutines_wake(s);
return ret;
}
