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From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
	linux-mm@kvack.org, Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Tejun Heo <tj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 01/12] locking/lockdep: Rework lockdep_set_novalidate_class()
Date: Sat, 10 Nov 2018 19:26:51 -0500	[thread overview]
Message-ID: <bc8ef8ae-c673-f4ae-fab1-3fe1bc884087@redhat.com> (raw)
In-Reply-To: <20181110141458.GE3339@worktop.programming.kicks-ass.net>

On 11/10/2018 09:14 AM, Peter Zijlstra wrote:
> On Thu, Nov 08, 2018 at 03:34:17PM -0500, Waiman Long wrote:
>> The current lockdep_set_novalidate_class() implementation is like
>> a hack. It assigns a special class key for that lock and calls
>> lockdep_init_map() twice.
> Ideally it would go away.. it is not thing that should be used.

Yes, I agree. Right now, lockdep_set_novalidate_class() is used in

drivers/base/core.c:    lockdep_set_novalidate_class(&dev->mutex);
drivers/md/bcache/btree.c:      lockdep_set_novalidate_class(&b->lock);
drivers/md/bcache/btree.c:     
lockdep_set_novalidate_class(&b->write_lock);

Do you know the history behind making them novalidate?

>
>> This patch changes the implementation to make it more general so that
>> it can be used by other special lock class types. A new "type" field
>> is added to both the lockdep_map and lock_class structures.
>>
>> The new field can now be used to designate a lock and a class object
>> as novalidate. The lockdep_set_novalidate_class() call, however, should
>> be called before lock initialization which calls lockdep_init_map().
> I don't really feel like this is something that should be made easier or
> better.

I am not saying that this patch make lockdep_set_novalidate_class()
easier to use. It is that terminal locks will share similar code path
and so I rework it so that they can checked together in one test instead
of 2 separate tests.

>> @@ -102,6 +100,8 @@ struct lock_class {
>>  	int				name_version;
>>  	const char			*name;
>>  
>> +	unsigned int			flags;
>> +
>>  #ifdef CONFIG_LOCK_STAT
>>  	unsigned long			contention_point[LOCKSTAT_POINTS];
>>  	unsigned long			contending_point[LOCKSTAT_POINTS];
> Esp. not at the cost of growing the data structures.
>
>

I did reduce the size by 16 bytes for 64-bit architecture in my previous
lockdep patch. Now I claw back 8 bytes for this new functionality.

Cheers,
Longman




  reply	other threads:[~2018-11-11  0:26 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-08 20:34 [RFC PATCH 00/12] locking/lockdep: Add a new class of terminal locks Waiman Long
2018-11-08 20:34 ` [RFC PATCH 01/12] locking/lockdep: Rework lockdep_set_novalidate_class() Waiman Long
2018-11-10 14:14   ` Peter Zijlstra
2018-11-11  0:26     ` Waiman Long [this message]
2018-11-11  1:28       ` Peter Zijlstra
2018-11-08 20:34 ` [RFC PATCH 02/12] locking/lockdep: Add a new terminal lock type Waiman Long
2018-11-10 14:17   ` Peter Zijlstra
2018-11-11  0:28     ` Waiman Long
2018-11-08 20:34 ` [RFC PATCH 03/12] locking/lockdep: Add DEFINE_TERMINAL_SPINLOCK() and related macros Waiman Long
2018-11-08 20:34 ` [RFC PATCH 04/12] printk: Make logbuf_lock a terminal lock Waiman Long
2018-11-08 20:34 ` [RFC PATCH 05/12] debugobjects: Mark pool_lock as " Waiman Long
2018-11-08 20:34 ` [RFC PATCH 06/12] debugobjects: Move printk out of db lock critical sections Waiman Long
2018-11-08 20:34 ` [RFC PATCH 07/12] locking/lockdep: Add support for nested terminal locks Waiman Long
2018-11-10 14:20   ` Peter Zijlstra
2018-11-11  0:30     ` Waiman Long
2018-11-11  1:30       ` Peter Zijlstra
2018-11-08 20:34 ` [RFC PATCH 08/12] debugobjects: Make object hash locks " Waiman Long
2018-11-08 20:34 ` [RFC PATCH 09/12] lib/stackdepot: Make depot_lock a terminal spinlock Waiman Long
2018-11-08 20:34 ` [RFC PATCH 10/12] locking/rwsem: Mark rwsem.wait_lock as a terminal lock Waiman Long
2018-11-08 20:34 ` [RFC PATCH 11/12] cgroup: Mark the rstat percpu lock as terminal Waiman Long
2018-11-08 20:34 ` [RFC PATCH 12/12] mm/kasan: Make quarantine_lock a terminal lock Waiman Long
2018-11-09  8:04 ` [RFC PATCH 00/12] locking/lockdep: Add a new class of terminal locks Ingo Molnar
2018-11-09 15:48   ` Waiman Long
2018-11-12  5:15     ` Ingo Molnar
2018-11-10 14:10   ` Peter Zijlstra
2018-11-10 23:35     ` Waiman Long
2018-11-12  5:10       ` Ingo Molnar
2018-11-12  5:53         ` Josh Poimboeuf
2018-11-12  6:30           ` Ingo Molnar
2018-11-12 22:22             ` Josh Poimboeuf
2018-11-12 22:56               ` Waiman Long

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