[openib-general] [PATCH] IB/ucm: fix deadlock in cleanup

[Sean Hefty]

Michael S. Tsirkin wrote:
> ib_ucm_cleanup_events has file_mutex while calling ib_destroy_cm_id.
> It seems this can deadlock since ib_destroy_cm_id flushes event
> handlers, and ib_ucm_event_handler needs file_mutex, too.
> 
> Signed-off-by: Michael S. Tsirkin <mst at mellanox.co.il>
> 
> ---
> 
> I'll be testing the following the next night - but it seems a right
> thing to do regardless of whether it fixes the issues I reported
> earlier. Sean, does this make sense to you? If yes, please ack for 2.6.19.

Yes - this looks right to me.

Acked-by: Sean Hefty <sean.hefty at intel.com>


> diff --git a/drivers/infiniband/core/ucm.c b/drivers/infiniband/core/ucm.c
> index ad4f4d5..0128288 100644
> --- a/drivers/infiniband/core/ucm.c
> +++ b/drivers/infiniband/core/ucm.c
> @@ -161,12 +161,14 @@ static void ib_ucm_cleanup_events(struct
>  				    struct ib_ucm_event, ctx_list);
>  		list_del(&uevent->file_list);
>  		list_del(&uevent->ctx_list);
> +		mutex_unlock(&ctx->file->file_mutex);
>  
>  		/* clear incoming connections. */
>  		if (ib_ucm_new_cm_id(uevent->resp.event))
>  			ib_destroy_cm_id(uevent->cm_id);
>  
>  		kfree(uevent);
> +		mutex_lock(&ctx->file->file_mutex);
>  	}
>  	mutex_unlock(&ctx->file->file_mutex);
>  }
> 
> 
>