Re: [PATCH 1/2] IB/rxe: Wait for tasklets to finish before tearing down QP

[Yuval Shaia <yuval.shaia-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

On Mon, Nov 28, 2016 at 09:37:23AM -0500, Andrew Boyer wrote:
> The system may crash when a malformed request is received and
> the error is detected by the responder.
> 
> NodeA: $ ibv_rc_pingpong -g 0 -d rxe0 -i 1 -n 1 -s 50000
> NodeB: $ ibv_rc_pingpong -g 0 -d rxe0 -i 1 -n 1 -s 1024 <NodeA_ip>
> 
> The responder generates a receive error on node B since the incoming
> SEND is oversized. If the client tears down the QP before the responder
> or the completer finish running, a page fault may occur.
> 
> The fix makes the destroy operation spin until the tasks complete, which
> appears to be original intent of the design.
> 
> Signed-off-by: Andrew Boyer <andrew.boyer-8PEkshWhKlo@public.gmane.org>
> ---
>  drivers/infiniband/sw/rxe/rxe_task.c | 19 +++++++++++++++++++
>  drivers/infiniband/sw/rxe/rxe_task.h |  1 +
>  2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_task.c b/drivers/infiniband/sw/rxe/rxe_task.c
> index 1e19bf8..1e9a28f 100644
> --- a/drivers/infiniband/sw/rxe/rxe_task.c
> +++ b/drivers/infiniband/sw/rxe/rxe_task.c
> @@ -121,6 +121,7 @@ int rxe_init_task(void *obj, struct rxe_task *task,
>  	task->arg	= arg;
>  	task->func	= func;
>  	snprintf(task->name, sizeof(task->name), "%s", name);
> +	task->destroyed	= false;
>  
>  	tasklet_init(&task->tasklet, rxe_do_task, (unsigned long)task);
>  
> @@ -132,11 +133,29 @@ int rxe_init_task(void *obj, struct rxe_task *task,
>  
>  void rxe_cleanup_task(struct rxe_task *task)
>  {
> +	unsigned long flags;
> +	bool idle = false;

The above initialization is not needed

Besides that:
Reviewed-by: Yuval Shaia <yuval.shaia-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>

> +
> +	/*
> +	 * Mark the task, then wait for it to finish. It might be
> +	 * running in a non-tasklet (direct call) context.
> +	 */
> +	task->destroyed = true;
> +
> +	do {
> +		spin_lock_irqsave(&task->state_lock, flags);
> +		idle = (task->state == TASK_STATE_START);
> +		spin_unlock_irqrestore(&task->state_lock, flags);
> +	} while (!idle);
> +
>  	tasklet_kill(&task->tasklet);
>  }
>  
>  void rxe_run_task(struct rxe_task *task, int sched)
>  {
> +	if (task->destroyed)
> +		return;
> +
>  	if (sched)
>  		tasklet_schedule(&task->tasklet);
>  	else
> diff --git a/drivers/infiniband/sw/rxe/rxe_task.h b/drivers/infiniband/sw/rxe/rxe_task.h
> index d14aa6d..08ff42d 100644
> --- a/drivers/infiniband/sw/rxe/rxe_task.h
> +++ b/drivers/infiniband/sw/rxe/rxe_task.h
> @@ -54,6 +54,7 @@ struct rxe_task {
>  	int			(*func)(void *arg);
>  	int			ret;
>  	char			name[16];
> +	bool			destroyed;
>  };
>  
>  /*
> -- 
> 1.8.3.1
> 
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