Re: [dpdk-dev] [PATCH 1/3] eal: fix lock issue for hot-unplug

[Matan Azrad <matan@mellanox.com>]

Hi Jeff

Can you detail more in the commit log that we can understand the deadlock scenario. And how does this commit fix it? 

> -----Original Message-----
> From: Jeff Guo <jia.guo@intel.com>
> Sent: Tuesday, November 6, 2018 8:07 AM
> To: konstantin.ananyev@intel.com; anatoly.burakov@intel.com; Thomas
> Monjalon <thomas@monjalon.net>; bernard.iremonger@intel.com;
> jingjing.wu@intel.com; wenzhuo.lu@intel.com
> Cc: ferruh.yigit@intel.com; dev@dpdk.org; jia.guo@intel.com;
> helin.zhang@intel.com; Matan Azrad <matan@mellanox.com>;
> shaopeng.he@intel.com
> Subject: [PATCH 1/3] eal: fix lock issue for hot-unplug
> 
> This patch will add missing unlock for hot-unplug handler, without this patch
> potential dead lock will occur when device be hotplug-in after device be hot-
> unplugged.
> 
> Fixes: 0fc54536b14a ("eal: add failure handling for hot-unplug")
> Signed-off-by: Jeff Guo <jia.guo@intel.com>
> ---
>  lib/librte_eal/linuxapp/eal/eal_dev.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/librte_eal/linuxapp/eal/eal_dev.c
> b/lib/librte_eal/linuxapp/eal/eal_dev.c
> index d589c69..2830c86 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_dev.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_dev.c
> @@ -258,7 +258,7 @@ dev_uev_handler(__rte_unused void *param)
>  			if (bus == NULL) {
>  				RTE_LOG(ERR, EAL, "Cannot find bus (%s)\n",
>  					busname);
> -				return;
> +				goto failure_handle_err;
>  			}
> 
>  			dev = bus->find_device(NULL, cmp_dev_name, @@
> -266,19 +266,23 @@ dev_uev_handler(__rte_unused void *param)
>  			if (dev == NULL) {
>  				RTE_LOG(ERR, EAL, "Cannot find device (%s)
> on "
>  					"bus (%s)\n", uevent.devname,
> busname);
> -				return;
> +				goto failure_handle_err;
>  			}
> 
>  			ret = bus->hot_unplug_handler(dev);
> -			rte_spinlock_unlock(&failure_handle_lock);
>  			if (ret) {
>  				RTE_LOG(ERR, EAL, "Can not handle hot-
> unplug "
>  					"for device (%s)\n", dev->name);
> -				return;
>  			}
> +			rte_spinlock_unlock(&failure_handle_lock);
>  		}
>  		rte_dev_event_callback_process(uevent.devname,
> uevent.type);
>  	}
> +
> +	return;
> +
> +failure_handle_err:
> +	rte_spinlock_unlock(&failure_handle_lock);
>  }
> 
>  int __rte_experimental
> --
> 2.7.4