From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH] vhost: fix race condition in fdset_add Date: Fri, 14 Dec 2018 11:08:52 +0100 Message-ID: <7a7a3181-1529-dd5f-b95f-9f8fef77fa8f@redhat.com> References: <1544112007-23177-1-git-send-email-matthias.gatto@outscale.com> <1f9db33f-b281-b794-bc00-ad83490c2fbd@redhat.com> <1fa47f8c-18a1-fbb4-1794-3324126cf9f1@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org, tiwei.bie@intel.com, zhihong.wang@intel.com, stable@dpdk.org To: Matthias Gatto Return-path: In-Reply-To: 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 12/14/18 11:07 AM, Matthias Gatto wrote: > On Fri, Dec 14, 2018 at 10:53 AM Maxime Coquelin > wrote: >> >> >> >> On 12/14/18 10:51 AM, Maxime Coquelin wrote: >>> >>> >>> On 12/14/18 10:32 AM, Matthias Gatto wrote: >>>> On Tue, Dec 11, 2018 at 7:11 PM Maxime Coquelin >>>> wrote: >>>>> >>>>> Hi Matthias, >>>>> >>>>> On 12/6/18 5:00 PM, Matthias Gatto wrote: >>>>>> fdset_add can call fdset_shrink_nolock which call fdset_move >>>>>> concurrently to poll that is call in fdset_event_dispatch. >>>>>> >>>>>> This patch add a mutex to protect poll from been call at the same time >>>>>> fdset_add call fdset_shrink_nolock. >>>>>> >>>>>> Signed-off-by: Matthias Gatto >>>>>> --- >>>>>> lib/librte_vhost/fd_man.c | 4 ++++ >>>>>> lib/librte_vhost/fd_man.h | 1 + >>>>>> lib/librte_vhost/socket.c | 1 + >>>>>> 3 files changed, 6 insertions(+) >>>>>> >>>>>> diff --git a/lib/librte_vhost/fd_man.c b/lib/librte_vhost/fd_man.c >>>>>> index 38347ab..55d4856 100644 >>>>>> --- a/lib/librte_vhost/fd_man.c >>>>>> +++ b/lib/librte_vhost/fd_man.c >>>>>> @@ -129,7 +129,9 @@ >>>>>> pthread_mutex_lock(&pfdset->fd_mutex); >>>>>> i = pfdset->num < MAX_FDS ? pfdset->num++ : -1; >>>>>> if (i == -1) { >>>>>> + pthread_mutex_lock(&pfdset->fd_pooling_mutex); >>>>>> fdset_shrink_nolock(pfdset); >>>>>> + pthread_mutex_unlock(&pfdset->fd_pooling_mutex); >>>>>> i = pfdset->num < MAX_FDS ? pfdset->num++ : -1; >>>>>> if (i == -1) { >>>>>> pthread_mutex_unlock(&pfdset->fd_mutex); >>>>>> @@ -246,7 +248,9 @@ >>>>>> numfds = pfdset->num; >>>>>> pthread_mutex_unlock(&pfdset->fd_mutex); >>>>>> >>>>>> + pthread_mutex_lock(&pfdset->fd_pooling_mutex); >>>>>> val = poll(pfdset->rwfds, numfds, 1000 /* millisecs */); >>>>>> + pthread_mutex_unlock(&pfdset->fd_pooling_mutex); >>>>> >>>>> Any reason we cannot use the existing fd_mutex? >>>> >>>> yes, using the existing fd_mutex would block fdset_add during the >>>> polling in >>>> fdset_event_dispatch. >>>> >>>> here fd_pooling_mutex block only fdset_shrink_nolock inside >>>> fdset_add which happen only in very rare occasions. >>> >>> >>> Thanks for the clarification: >>> >>> Reviewed-by: Maxime Coquelin >> >> I guess we need to cc: stable, can you help with specifying which >> commit it fixes? >> >> Thanks in advance, >> Maxime >> > > this commit 1b815b89599cdd9b54e5aa70f5b97088225b2bcc > which was actually a commit I've made, sorry for that. Don't be sorry, your contributions are welcome! I'll fixup the commit message with adding Fixes line. Thanks, Maxime > Thanks for the review, > > Matthias >>> Maxime