[PATCH] mailbox: always wait in mbox_send_message for blocking tx mode

[PATCH] mailbox: always wait in mbox_send_message for blocking tx mode

[Sudeep Holla]

There exists a race when msg_submit return immediately as there was an
active request being processed which may have completed just before it's
checked again in mbox_send_message. This will result in return to the
caller without waiting in mbox_send_message even when it's blocking Tx.

This patch fixes the issue by making use of non-negative token returned
by add_to_rbuf to check if the request was queued and block always if
so in blocking Tx mode.

Fixes: 2b6d83e2b8b7 ("mailbox: Introduce framework for mailbox")
Cc: Jassi Brar <jassisinghbrar@gmail.com>
Reported-by: Alexey Klimov <alexey.klimov@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 drivers/mailbox/mailbox.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 4671f8a12872..d5895791ab5d 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -260,7 +260,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg)
 
 	msg_submit(chan);
 
-	if (chan->cl->tx_block && chan->active_req) {
+	if (chan->cl->tx_block && t >= 0) {
 		unsigned long wait;
 		int ret;
 
-- 
2.7.4

Re: [PATCH] mailbox: always wait in mbox_send_message for blocking tx mode

[Alexey Klimov]

Hi Sudeep,

thanks for sending this patch.

On Mon, Mar 20, 2017 at 03:40:10PM +0000, Sudeep Holla wrote:
> There exists a race when msg_submit return immediately as there was an
> active request being processed which may have completed just before it's
> checked again in mbox_send_message. This will result in return to the
> caller without waiting in mbox_send_message even when it's blocking Tx.
> 
> This patch fixes the issue by making use of non-negative token returned
> by add_to_rbuf to check if the request was queued and block always if
> so in blocking Tx mode.
> 
> Fixes: 2b6d83e2b8b7 ("mailbox: Introduce framework for mailbox")
> Cc: Jassi Brar <jassisinghbrar@gmail.com>
> Reported-by: Alexey Klimov <alexey.klimov@arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> ---
>  drivers/mailbox/mailbox.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
> index 4671f8a12872..d5895791ab5d 100644
> --- a/drivers/mailbox/mailbox.c
> +++ b/drivers/mailbox/mailbox.c
> @@ -260,7 +260,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg)
>  
>  	msg_submit(chan);
>  
> -	if (chan->cl->tx_block && chan->active_req) {
> +	if (chan->cl->tx_block && t >= 0) {

What do you think about removing t>=0 at all?
If add_to_rbuf() above returns negative number then we won't reach this point
in code at all and quit this function with error. If execution reaches this line then
we can say that t is definetely >= 0 and maybe it shouldn't be checked.


Best regards,
Alexey

Re: [PATCH] mailbox: always wait in mbox_send_message for blocking tx mode

[Sudeep Holla]

On 20/03/17 18:47, Alexey Klimov wrote:
> Hi Sudeep,
> 
> thanks for sending this patch.
> 
> On Mon, Mar 20, 2017 at 03:40:10PM +0000, Sudeep Holla wrote:
>> There exists a race when msg_submit return immediately as there was an
>> active request being processed which may have completed just before it's
>> checked again in mbox_send_message. This will result in return to the
>> caller without waiting in mbox_send_message even when it's blocking Tx.
>>
>> This patch fixes the issue by making use of non-negative token returned
>> by add_to_rbuf to check if the request was queued and block always if
>> so in blocking Tx mode.
>>
>> Fixes: 2b6d83e2b8b7 ("mailbox: Introduce framework for mailbox")
>> Cc: Jassi Brar <jassisinghbrar@gmail.com>
>> Reported-by: Alexey Klimov <alexey.klimov@arm.com>
>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
>> ---
>>  drivers/mailbox/mailbox.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
>> index 4671f8a12872..d5895791ab5d 100644
>> --- a/drivers/mailbox/mailbox.c
>> +++ b/drivers/mailbox/mailbox.c
>> @@ -260,7 +260,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg)
>>  
>>  	msg_submit(chan);
>>  
>> -	if (chan->cl->tx_block && chan->active_req) {
>> +	if (chan->cl->tx_block && t >= 0) {
> 
> What do you think about removing t>=0 at all?
> If add_to_rbuf() above returns negative number then we won't reach this point
> in code at all and quit this function with error. If execution reaches this line then
> we can say that t is definetely >= 0 and maybe it shouldn't be checked.

Ah right, sorry I missed to see that, will fix it.

-- 
Regards,
Sudeep