Please see https://gerrit.fd.io/r/c/vpp/+/38507
-----Original Message----- From: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> <vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> > On Behalf Of Hao Tian Sent: Wednesday, March 15, 2023 10:14 PM To: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> Subject: Re: [vpp-dev] Race condition between bihash deletion and searching - misuse or bug? Hi Dave, Thanks for your work. I am ready to test whenever needed. Best regards, Hao Tian ________________________________________ From: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> <vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> > on behalf of Dave Barach <v...@barachs.net <mailto:v...@barachs.net> > Sent: Thursday, March 16, 2023 7:02 AM To: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> Subject: Re: [vpp-dev] Race condition between bihash deletion and searching - misuse or bug? I'm doing a bit of work to straighten out the template, hopefully without causing a measurable performance regression. Hao's test code is a bit of a corner-case: there is exactly one record in the database which the code thrashes as hard as possible. D. -----Original Message----- From: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> <vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> > On Behalf Of Andrew Yourtchenko Sent: Wednesday, March 15, 2023 12:33 PM To: vpp-dev@lists.fd.io <mailto:vpp-dev@lists.fd.io> Subject: Re: [vpp-dev] Race condition between bihash deletion and searching - misuse or bug? Hao, I noticed the same behavior when stress-testing the multi thread session handling for the ACL plugin a while ago. I thought this trade off is there to avoid having to do the hard locks in bihash code, rather than it being a bug. As you say - the special value comes only if the deletion is in progress, and it is always the same. So I just treated that case in my code same as “not found”. My logic was: if an entry is just in process of being deleted, there is very little use for its old value anyway. --a > On 15 Mar 2023, at 14:45, Hao Tian <tianhao...@outlook.com > <mailto:tianhao...@outlook.com> > wrote: > > Hi, > > I tried but could not come up with any way that is able to ensure the kvp > being valid upon return without using the full bucket lock. > > Maybe we can make a copy of the value before returning, validate the copy and > return that copy instead. Critical section can be shrinked to cover only the > copying process, which seems to perform better, but I'm not sure if this is > the best approach. > > Could you please shed some light here? Thanks! > > Regards, > Hao Tian >
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