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From: Joel Fernandes <joel@joelfernandes.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org, rcu@vger.kernel.org,
"Paul E. McKenney" <paulmck@kernel.org>,
Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
Qian Cai <cai@lca.pw>, Ingo Molnar <mingo@redhat.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH] locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps()
Date: Mon, 16 Mar 2020 11:01:10 -0400 [thread overview]
Message-ID: <20200316150110.GB134626@google.com> (raw)
In-Reply-To: <20200316135507.GF12561@hirez.programming.kicks-ass.net>
On Mon, Mar 16, 2020 at 02:55:07PM +0100, Peter Zijlstra wrote:
> On Sat, Mar 14, 2020 at 09:04:22PM -0400, Joel Fernandes wrote:
> > On Fri, Mar 13, 2020 at 10:33:25AM +0100, Peter Zijlstra wrote:
>
> > Thanks Peter and Boqun, the below patch makes sense to me. Just had some nits
> > below, otherwise:
> > > @@ -1719,11 +1725,11 @@ unsigned long lockdep_count_forward_deps
> > > this.class = class;
> > >
> > > raw_local_irq_save(flags);
> > > - current->lockdep_recursion = 1;
> > > + current->lockdep_recursion++;
> > > arch_spin_lock(&lockdep_lock);
> > > ret = __lockdep_count_forward_deps(&this);
> > > arch_spin_unlock(&lockdep_lock);
> > > - current->lockdep_recursion = 0;
> > > + current->lockdep_recursion--;
> >
> > This doesn't look like it should recurse. Why not just use the
> > lockdep_recursion_finish() helper here?
>
> I chose to only add that to the sites that check recursion on entry.
Makes sense, thank you Peter.
- Joel
next prev parent reply other threads:[~2020-03-16 15:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 15:12 Boqun Feng
2020-03-13 9:33 ` Peter Zijlstra
2020-03-15 1:04 ` Joel Fernandes
2020-03-16 13:55 ` Peter Zijlstra
2020-03-16 15:01 ` Joel Fernandes [this message]
2020-03-20 12:58 ` [tip: locking/core] locking/lockdep: Fix bad recursion pattern tip-bot2 for Peter Zijlstra
2020-03-13 10:21 ` [PATCH] locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps() Peter Zijlstra
2020-03-20 12:58 ` [tip: locking/core] locking/lockdep: Rework lockdep_lock tip-bot2 for Peter Zijlstra
2020-03-20 12:58 ` [tip: locking/core] locking/lockdep: Avoid recursion in lockdep_count_{for,back}ward_deps() tip-bot2 for Boqun Feng
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