From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tan, Jianfeng" Subject: Re: [PATCH v3 2/5] bus/vdev: add lock on vdev device list Date: Fri, 20 Apr 2018 23:23:53 +0800 Message-ID: <7f684956-4918-beda-e520-140aa4e22e16@intel.com> 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: 7bit Cc: thomas@monjalon.net To: "Burakov, Anatoly" , dev@dpdk.org Return-path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id E5CBFD4AA for ; Fri, 20 Apr 2018 17:24:08 +0200 (CEST) In-Reply-To: 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 4/20/2018 11:16 PM, Burakov, Anatoly wrote: > 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 :) I might have mixed this with another case. I think it's a fair point. > > 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. I'll change the implementation. Thanks, Jianfeng