Re: [PATCH] IB/rdmavt: add lock to call to rvt_error_qp to prevent a race condition

[Dennis Dalessandro]

On 4/4/22 9:42 AM, Jason Gunthorpe wrote:
> On Mon, Feb 28, 2022 at 05:53:30PM +0100, Niels Dossche wrote:
>> The documentation of the function rvt_error_qp says both r_lock and
>> s_lock need to be held when calling that function.
>> It also asserts using lockdep that both of those locks are held.
>> However, the commit I referenced in Fixes accidentally makes the call
>> to rvt_error_qp in rvt_ruc_loopback no longer covered by r_lock.
>> This results in the lockdep assertion failing and also possibly in a
>> race condition.
>>
>> Fixes: d757c60eca9b ("IB/rdmavt: Fix concurrency panics in QP post_send and modify to error")
>> Signed-off-by: Niels Dossche <dossche.niels@xxxxxxxxx>
>> ---
>>  drivers/infiniband/sw/rdmavt/qp.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> Dennis?

For this one:

Acked-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxxxxxxxxxxxxx>

> And this too:
> 
> https://patchwork.kernel.org/project/linux-rdma/patch/20220228195144.71946-1-dossche.niels@xxxxxxxxx/

I think is correct as well. Not thrilled with the lock, unlock, lock. Stuff, but
this whole unwind code needs a once-over so for this patch as well:

Acked-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxxxxxxxxxxxxx>

Thanks Niels for finding and fixing these issues!

-Denny