Re: [PATCH for-rc] IB/hfi1: Fix another case where pq is left on waitlist

From: Jason Gunthorpe <jgg@ziepe.ca>
To: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: dledford@redhat.com, linux-rdma@vger.kernel.org
Subject: Re: [PATCH for-rc] IB/hfi1: Fix another case where pq is left on waitlist
Date: Wed, 6 May 2020 11:46:57 -0300	[thread overview]
Message-ID: <20200506144657.GA14279@ziepe.ca> (raw)
In-Reply-To: <20200504130917.175613.43231.stgit@awfm-01.aw.intel.com>

On Mon, May 04, 2020 at 09:09:17AM -0400, Mike Marciniszyn wrote:
> The commit noted below fixed a case where a pq is left on
> the sdma wait list.
> 
> It however missed another case.
> 
> user_sdma_send_pkts() has two calls from hfi1_user_sdma_process_request().
> 
> If the first one fails as indicated by -EBUSY, the pq will be placed on
> the waitlist as by design.
> 
> If the second call then succeeds, the pq is still on the waitlist
> setting up a race with the interrupt handler if a subsequent request uses
> a different SDMA engine
> 
> Fix by deleting the first call.
> 
> The use of pcount and the intent to send a short burst of packets followed
> by the larger balance of packets was never correctly implemented, because
> the two calls always send pcount packets no matter what.  A subsequent
> patch will correct that issue.
> 
> Fixes: 9a293d1e21a6 ("IB/hfi1: Ensure pq is not left on waitlist")
> Cc: <stable@vger.kernel.org>
> Reviewed-by: Kaike Wan <kaike.wan@intel.com>
> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
> ---
>  drivers/infiniband/hw/hfi1/user_sdma.c |    4 ----
>  1 file changed, 4 deletions(-)

Applied to for-rc, thanks

Jason