Re: [PATCH 1/1] Revert "RDMA/rxe: Add workqueue support for rxe tasks"

[Bart Van Assche <bvanassche@xxxxxxx>]

On 9/26/23 11:34, Bob Pearson wrote:
> I am working to try to reproduce the KASAN warning. Unfortunately,
> so far I am not able to see it in Ubuntu + Linus' kernel (as you 
> described) on metal. The config file is different but copies the 
> CONFIG_KASAN_xxx exactly as yours. With KASAN enabled it hangs on 
> every iteration of srp/002 but without a KASAN warning. I am now 
> building an openSuSE VM for qemu and will see if that causes the 
> warning.

Hi Bob,

Did you try to understand the report that I shared? My conclusion from
the report is that when using tasklets rxe_completer() only runs after
rxe_requester() has finished and also that when using work queues that
rxe_completer() may run concurrently with rxe_requester(). This patch
seems to fix all issues that I ran into with the rdma_rxe workqueue
patch (I have not tried to verify the performance implications of this
patch):

diff --git a/drivers/infiniband/sw/rxe/rxe_task.c 
b/drivers/infiniband/sw/rxe/rxe_task.c
index 1501120d4f52..6cd5d5a7a316 100644
--- a/drivers/infiniband/sw/rxe/rxe_task.c
+++ b/drivers/infiniband/sw/rxe/rxe_task.c
@@ -10,7 +10,7 @@ static struct workqueue_struct *rxe_wq;

 int rxe_alloc_wq(void)
 {
-       rxe_wq = alloc_workqueue("rxe_wq", WQ_UNBOUND, WQ_MAX_ACTIVE);
+       rxe_wq = alloc_workqueue("rxe_wq", WQ_UNBOUND, 1);
        if (!rxe_wq)
                return -ENOMEM;

Thanks,

Bart.