[Xen-devel] [PATCH v3 2/2] xenbus: req->err should be updated before req->state

[Dongli Zhang <dongli.zhang@xxxxxxxxxx>]

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.

Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
---
 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);
        }
-- 
2.17.1


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