The read operation to "req->type" is protected by
the lock on line 128, but the write operation to
this data on line 118 is not protected by the lock.
Thus, there may exist a data race for "req->type".
To fix this data race, the write operation to "req->type"
should be also protected by the lock.
Signed-off-by: Jia-Ju Bai <[email protected]>
---
drivers/xen/xenbus/xenbus_xs.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 49a3874ae6bb..274cdfee08b1 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -115,10 +115,10 @@ static uint32_t xs_request_enter(struct xb_req_data *req)
{
uint32_t rq_id;
- req->type = req->msg.type;
-
spin_lock(&xs_state_lock);
+ req->type = req->msg.type;
+
while (!xs_state_users && xs_suspend_active) {
spin_unlock(&xs_state_lock);
wait_event(xs_state_enter_wq, xs_suspend_active == 0);
--
2.17.0
On 08/05/18 05:34, Jia-Ju Bai wrote:
> The read operation to "req->type" is protected by
> the lock on line 128, but the write operation to
> this data on line 118 is not protected by the lock.
> Thus, there may exist a data race for "req->type".
>
> To fix this data race, the write operation to "req->type"
> should be also protected by the lock.
No, xs_request_enter() is never called for a request already visible to
another thread or processor. So no race exists.
Juergen
>
> Signed-off-by: Jia-Ju Bai <[email protected]>
> ---
> drivers/xen/xenbus/xenbus_xs.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
> index 49a3874ae6bb..274cdfee08b1 100644
> --- a/drivers/xen/xenbus/xenbus_xs.c
> +++ b/drivers/xen/xenbus/xenbus_xs.c
> @@ -115,10 +115,10 @@ static uint32_t xs_request_enter(struct xb_req_data *req)
> {
> uint32_t rq_id;
>
> - req->type = req->msg.type;
> -
> spin_lock(&xs_state_lock);
>
> + req->type = req->msg.type;
> +
> while (!xs_state_users && xs_suspend_active) {
> spin_unlock(&xs_state_lock);
> wait_event(xs_state_enter_wq, xs_suspend_active == 0);
>
On 2018/5/8 15:02, Juergen Gross wrote:
> On 08/05/18 05:34, Jia-Ju Bai wrote:
>> The read operation to "req->type" is protected by
>> the lock on line 128, but the write operation to
>> this data on line 118 is not protected by the lock.
>> Thus, there may exist a data race for "req->type".
>>
>> To fix this data race, the write operation to "req->type"
>> should be also protected by the lock.
> No, xs_request_enter() is never called for a request already visible to
> another thread or processor. So no race exists.
Okay, thanks for your reply.
Best wishes,
Jia-Ju Bai