From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Burakov, Anatoly" Subject: Re: [PATCH v3 2/5] bus/vdev: add lock on vdev device list Date: Fri, 20 Apr 2018 16:16:38 +0100 Message-ID: References: <1520177405-59091-1-git-send-email-jianfeng.tan@intel.com> <1524156618-81402-1-git-send-email-jianfeng.tan@intel.com> <1524156618-81402-3-git-send-email-jianfeng.tan@intel.com> <0025fac5-c007-c793-c3f7-2168343a1026@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: thomas@monjalon.net To: "Tan, Jianfeng" , dev@dpdk.org Return-path: Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by dpdk.org (Postfix) with ESMTP id 598877ECB for ; Fri, 20 Apr 2018 17:16:42 +0200 (CEST) In-Reply-To: <0025fac5-c007-c793-c3f7-2168343a1026@intel.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 20-Apr-18 3:19 PM, Tan, Jianfeng wrote: > > > On 4/20/2018 4:26 PM, Burakov, Anatoly wrote: >> On 19-Apr-18 5:50 PM, Jianfeng Tan wrote: >>> As we could add virtual devices from different threads now, we >>> add a spin lock to protect the vdev device list. >>> >>> Suggested-by: Anatoly Burakov >>> Signed-off-by: Jianfeng Tan >>> Reviewed-by: Qi Zhang >>> --- >> >> <...> >> >>> +/* The caller shall be responsible for thread-safe */ >>>   static struct rte_vdev_device * >>>   find_vdev(const char *name) >>>   { >>> @@ -203,10 +206,6 @@ rte_vdev_init(const char *name, const char *args) >>>       if (name == NULL) >>>           return -EINVAL; >>>   -    dev = find_vdev(name); >>> -    if (dev) >>> -        return -EEXIST; >>> - >>>       devargs = alloc_devargs(name, args); >>>       if (!devargs) >>>           return -ENOMEM; >>> @@ -221,16 +220,28 @@ rte_vdev_init(const char *name, const char *args) >>>       dev->device.numa_node = SOCKET_ID_ANY; >>>       dev->device.name = devargs->name; >>>   +    rte_spinlock_lock(&vdev_device_list_lock); >>> +    if (find_vdev(name)) { >>> +        rte_spinlock_unlock(&vdev_device_list_lock); >>> +        ret = -EEXIST; >>> +        goto fail; >>> +    } >>> +    TAILQ_INSERT_TAIL(&vdev_device_list, dev, next); >>> +    rte_spinlock_unlock(&vdev_device_list_lock); >>> + >> >> I wonder if is possible to just leave the tailq locked until you >> either insert the device into tailq, or figure out that it's not >> possible? Seems like doing two locks here is unnecessary, unless >> vdev_probe_all_drivers needs this tailq unlocked... > > My opinion is that we don't know what could be done in driver probe(). > It could possibly insert a new vdev (it does not happen now, but could > happen in future?). So here, we call this with tailq unlocked. Or we > keep it as simple as possible as you say? I thought this code was responsible for inserting vdevs? I think it would be generally bad design to insert vdev while inserting vdev :) That said, it's a fair point, and i don't have a strong opinion on this, so you can leave it as is if you want. -- Thanks, Anatoly