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From: Bart Van Assche <bvanassche@acm.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	mingo@redhat.com, tj@kernel.org, longman@redhat.com,
	johannes.berg@intel.com, linux-kernel@vger.kernel.org,
	Paul McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v6 00/16] locking/lockdep: Add support for dynamic keys
Date: Wed, 13 Feb 2019 14:32:22 -0800	[thread overview]
Message-ID: <1550097142.31902.55.camel@acm.org> (raw)
In-Reply-To: <20190208114315.GD6972@fuggles.cambridge.arm.com>

On Fri, 2019-02-08 at 11:43 +0000, Will Deacon wrote:
> I've also been trying to understand why it's necessary to check both of the
> pending_free entries, and I'm still struggling somewhat. It's true that the
> wakeup in get_pending_free_lock() could lead to both entries being used
> without the RCU call back running in between, however in this scenario then
> any list entries marked for freeing in the first pf will have been unhashed
> and therefore made unreachable to look_up_lock_class().
> 
> So I think the concern remains that entries are somehow remaining visible
> after being zapped.
> 
> You mentioned earlier in the thread that people actually complained about
> list corruption if you only checked the current pf:
> 
>   | The list_del_rcu() call must only happen once. I ran into complaints
>   | reporting that the list_del_rcu() call triggered list corruption. This
>   | change made these complaints disappear.
> 
> Do you have any more details about these complaints (e.g. kernel logs etc)?
> Failing that, any idea how to reproduce them?

Hi Will,

Since elements of the list_entries[] array are always accessed with the graph
lock held, how about removing the list_entries_being_freed bitmap and making
zap_class() clear the appropriate bits in the list_entries_in_use bitmap?

Thanks,

Bart.

      parent reply	other threads:[~2019-02-13 22:32 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-09 21:01 [PATCH v6 00/16] locking/lockdep: Add support for dynamic keys Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 01/16] locking/lockdep: Fix reported required memory size Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 02/16] locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 03/16] locking/lockdep: Make zap_class() remove all matching lock order entries Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 04/16] locking/lockdep: Reorder struct lock_class members Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 05/16] locking/lockdep: Initialize the locks_before and locks_after lists earlier Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 06/16] locking/lockdep: Split lockdep_free_key_range() and lockdep_reset_lock() Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 07/16] locking/lockdep: Make it easy to detect whether or not inside a selftest Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 08/16] locking/lockdep: Free lock classes that are no longer in use Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 09/16] locking/lockdep: Reuse list entries " Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 10/16] locking/lockdep: Introduce lockdep_next_lockchain() and lock_chain_count() Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 11/16] locking/lockdep: Reuse lock chains that have been freed Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 12/16] locking/lockdep: Check data structure consistency Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 13/16] locking/lockdep: Verify whether lock objects are small enough to be used as class keys Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 14/16] locking/lockdep: Add support for dynamic keys Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 15/16] kernel/workqueue: Use dynamic lockdep keys for workqueues Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 16/16] lockdep tests: Test dynamic key registration Bart Van Assche
2019-01-11 12:48 ` [PATCH v6 00/16] locking/lockdep: Add support for dynamic keys Peter Zijlstra
2019-01-11 15:55   ` Bart Van Assche
2019-01-11 16:55     ` Peter Zijlstra
2019-01-11 17:01       ` Bart Van Assche
2019-01-14 12:52         ` Peter Zijlstra
2019-01-14 16:52           ` Bart Van Assche
2019-01-18  9:48             ` Peter Zijlstra
2019-01-19  2:34               ` Bart Van Assche
2019-02-01 12:15                 ` Peter Zijlstra
2019-02-03 17:36                   ` Bart Van Assche
2019-02-08 11:43                     ` Will Deacon
2019-02-08 16:31                       ` Bart Van Assche
2019-02-13 22:32                       ` Bart Van Assche [this message]

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