netdev - Re: [PATCH 1/2] genl: Fix genl dumpit() locking.

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Message-ID: <1377193906.14110.27.camel@jlt4.sipsolutions.net>
Date:	Thu, 22 Aug 2013 19:51:46 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Pravin Shelar <pshelar@...ira.com>
Cc:	netdev <netdev@...r.kernel.org>, Jesse Gross <jesse@...ira.com>
Subject: Re: [PATCH 1/2] genl: Fix genl dumpit() locking.

On Thu, 2013-08-22 at 10:42 -0700, Pravin Shelar wrote:
> On Thu, Aug 22, 2013 at 12:36 AM, Johannes Berg
> <johannes@...solutions.net> wrote:
> > On Wed, 2013-08-21 at 20:58 -0700, Pravin B Shelar wrote:
> >> In case of genl-family with parallel ops off, dumpif() callback
> >> is expected to run under genl_lock, But commit def3117493eafd9df
> >> (genl: Allow concurrent genl callbacks.) changed this behaviour
> >> where only first dumpit() op was called under genl-lock.
> >> For subsequent dump, only nlk->cb_lock was taken.
> >> Following patch fixes it by defining locked dumpit() and done()
> >> callback which takes care of genl-locking.
> >
> > As I've commented over in the other thread, I really think this is the
> > wrong thing to do. It was never the case that dumpit() was actually
> > locked under genl_lock(), and adding it doesn't really help anyone.
> >
> If you look at commit def3117493eafd9df , it removes assignment of
> cb_mutex to genl_mutex. Thats how genl-dump operation was called under
> genl_mutex.

By the way - why? This just means that netlink will allocate another
lock to lock it all, so it's not a very useful change?

johannes

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