Hi,
On 03/03/2020 01:58, Dongli Zhang wrote:
This patch adds the barrier to guarantee that req->err is always updated
before req->state.
Otherwise, read_reply() would not return ERR_PTR(req->err) but
req->body, when process_writes()->xb_write() is failed.
The memory barrier below looks good. However, as mentionned in patch #1,
barrier() is not the correct barrier to pair with virt_wmb().
Signed-off-by: Dongli Zhang <dongli.zh...@oracle.com>
---
drivers/xen/xenbus/xenbus_comms.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/xen/xenbus/xenbus_comms.c
b/drivers/xen/xenbus/xenbus_comms.c
index 852ed161fc2a..eb5151fc8efa 100644
--- a/drivers/xen/xenbus/xenbus_comms.c
+++ b/drivers/xen/xenbus/xenbus_comms.c
@@ -397,6 +397,8 @@ static int process_writes(void)
if (state.req->state == xb_req_state_aborted)
kfree(state.req);
else {
+ /* write err, then update state */
+ virt_wmb();
state.req->state = xb_req_state_got_reply;
wake_up(&state.req->wq);
}
Cheers,
--
Julien Grall
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