netdev - Re: [PATCH] iavf: fix locking of critical sections

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Message-ID: <20210316150210.00007249@intel.com>
Date:   Tue, 16 Mar 2021 15:02:10 -0700
From:   Jesse Brandeburg <jesse.brandeburg@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Stefan Assmann <sassmann@...nic.de>,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        anthony.l.nguyen@...el.com, lihong.yang@...el.com,
        slawomirx.laba@...el.com, nicholas.d.nunley@...el.com
Subject: Re: [PATCH] iavf: fix locking of critical sections

Jakub Kicinski wrote:
> > > I personally think that the overuse of flags in Intel drivers brings
> > > nothing but trouble. At which point does it make sense to just add a
> > > lock / semaphore here rather than open code all this with no clear
> > > semantics? No code seems to just test the __IAVF_IN_CRITICAL_TASK flag,
> > > all the uses look like poor man's locking at a quick grep. What am I
> > > missing?
> > 
> > I agree with you that the locking could be done with other locking
> > mechanisms just as good. I didn't invent the current method so I'll let
> > Intel comment on that part, but I'd like to point out that what I'm
> > making use of is fixing what is currently in the driver.
> 
> Right, I should have made it clear that I don't blame you for the
> current state of things. Would you mind sending a patch on top of 
> this one to do a conversion to a semaphore? 
> 
> Intel folks any opinions?

I know Slawomir has been working closely with Stefan on figuring out
the right ways to fix this code.  Hopefully he can speak for himself,
but I know he's on Europe time.

As for conversion to mutexes I'm a big fan, and as long as we don't
have too many collisions with the RTNL lock I think it's a reasonable
improvement to do, and if Stefan doesn't want to work on it, we can
look into whether Slawomir or his team can.