From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Jens Axboe <axboe@fb.com>, "J. R. Okajima" <hooanon05g@gmail.com>,
linux-kernel@vger.kernel.org, darrick.wong@oracle.com,
david@fromorbit.com, dave@stgolabs.net
Subject: Re: Q: lockdep_assert_held_read() after downgrade_write()
Date: Tue, 31 Jan 2017 15:26:37 +0100 [thread overview]
Message-ID: <20170131142637.GP6515@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <9e2f505e-3d1f-3573-661a-b2ad185566b1@redhat.com>
On Tue, Jan 31, 2017 at 09:23:08AM -0500, Waiman Long wrote:
> On 01/31/2017 06:25 AM, Peter Zijlstra wrote:
> > @@ -40,8 +40,10 @@ static inline void rwsem_set_reader_owned(struct rw_semaphore *sem)
> > * do a write to the rwsem cacheline when it is really necessary
> > * to minimize cacheline contention.
> > */
> > - if (sem->owner != RWSEM_READER_OWNED)
> > + if (sem->owner != RWSEM_READER_OWNED) {
> > + WARN_ON_ONCE(sem->owner != current);
> > WRITE_ONCE(sem->owner, RWSEM_READER_OWNED);
> > + }
> > }
> >
> > static inline bool rwsem_owner_is_writer(struct task_struct *owner)
>
> I don't think you can do a WARN_ON_ONCE() check for sem->owner !=
> current here. If the rwsem starts from an unlock state, sem->owner will
> be NULL and an incorrect warning message will be printed.
Argh, I only looked at the downgrade_write() user and forgot to look if
it was used elsewhere.
next prev parent reply other threads:[~2017-01-31 14:26 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-30 21:25 Q: lockdep_assert_held_read() after downgrade_write() J. R. Okajima
2017-01-30 21:30 ` Jens Axboe
2017-01-31 10:36 ` Peter Zijlstra
2017-01-31 11:25 ` Peter Zijlstra
2017-01-31 14:23 ` Waiman Long
2017-01-31 14:26 ` Peter Zijlstra [this message]
2017-01-31 15:40 ` J. R. Okajima
2017-01-31 16:32 ` Peter Zijlstra
2017-02-02 16:33 ` J. R. Okajima
2017-02-02 16:38 ` [PATCH 1/3] lockdep: consolidate by new find_held_lock() J. R. Okajima
2017-02-02 16:38 ` [PATCH 2/3] lockdep: consolidate by new validate_held_lock() J. R. Okajima
2017-02-14 12:09 ` Peter Zijlstra
2017-03-16 11:25 ` [tip:locking/core] locking/lockdep: Factor out the validate_held_lock() helper function tip-bot for J. R. Okajima
2017-02-02 16:38 ` [PATCH 3/3] lockdep: new annotation lock_downgrade() J. R. Okajima
2017-02-02 17:59 ` kbuild test robot
2017-02-02 18:45 ` Peter Zijlstra
2017-02-02 21:05 ` J. R. Okajima
2017-02-14 12:11 ` Peter Zijlstra
2017-03-16 11:25 ` [tip:locking/core] locking/lockdep: Add new check to lock_downgrade() tip-bot for J. R. Okajima
2017-03-16 11:24 ` [tip:locking/core] locking/lockdep: Factor out the find_held_lock() helper function tip-bot for J. R. Okajima
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