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From: Byungchul Park <byungchul.park@lge.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>,
	mingo@kernel.org, linux-kernel@vger.kernel.org,
	walken@google.com
Subject: Re: [PATCH] lockdep: Add a document describing crossrelease feature
Date: Wed, 6 Jul 2016 17:12:26 +0900	[thread overview]
Message-ID: <20160706081226.GC2279@X58A-UD3R> (raw)
In-Reply-To: <20160706075608.GE30921@twins.programming.kicks-ass.net>

On Wed, Jul 06, 2016 at 09:56:08AM +0200, Peter Zijlstra wrote:
> On Wed, Jul 06, 2016 at 02:33:29PM +0900, Byungchul Park wrote:
> > On Wed, Jul 06, 2016 at 11:17:10AM +0900, Byungchul Park wrote:
> > > 
> > > lock(A)
> > > wait_for(B)
> > > ~~~~~~~~~~~~~~~~~~~~~~~~ <- serialized by atomic operation
> > > 		lock(A)
> > > 		unlock(A)
> > > 		wake(B)
> > > unlock(A)
> > 
> > By the way, I have a question. Is there anyone who could answer it?
> > 
> > I want to serialize between two context's lock operations, for example,
> > 
> > 	context A	context B
> > 	--------------	--------------
> > 	lock A
> > 	lock B		...
> > 	lock C
> > 	atomic_inc_return
> > 	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <- serialization
> > 			atomic_read
> > 			lock D
> > 	...		lock E
> > 			lock F
> > 
> > so that we can see these in the order like A -> B -> C -> D -> E -> F.
> > 
> > atomic_inc_return() is used after lock C in context A, and atomic_read()
> > is used before lock D in context B. And I want to make it serialized when
> > the atomic_read() can see the increased value.
> > 
> > Can I use smp_mb__after_atomic() just after atomic_read() 
> 
> No. atomic_set() and atomic_read() are not RmW operations.
> 
> > or should I use
> > smp_mb()? I think anyway I have to choose one of them for that ordering.
> 
> smp_load_acquire(), if that observes the increment it will ensure D
> comes after etc..
> 
> Also, atomic_read() _could_ be enough, if its part of a control
> dependency, because LOCK very much involves a store, so the load->store
> order provided by the control dependency will already order things.

Indeed. Thank you very much.

I can rely on the control dependency if possible. I will check it.

Thank you,
Byungchul

      reply	other threads:[~2016-07-06  8:14 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-20  4:55 [RFC 00/12] lockdep: Implement crossrelease feature Byungchul Park
2016-06-20  4:55 ` [RFC 01/12] lockdep: Refactor lookup_chain_cache() Byungchul Park
2016-06-20  4:55 ` [RFC 02/12] lockdep: Add a function building a chain between two hlocks Byungchul Park
2016-06-20  4:55 ` [RFC 03/12] lockdep: Make check_prev_add can use a stack_trace of other context Byungchul Park
2016-06-20  4:55 ` [RFC 04/12] lockdep: Make save_trace can copy from other stack_trace Byungchul Park
2016-06-20  4:55 ` [RFC 05/12] lockdep: Implement crossrelease feature Byungchul Park
2016-06-30 13:03   ` Peter Zijlstra
2016-06-30 23:28     ` Byungchul Park
2016-06-20  4:55 ` [RFC 06/12] lockdep: Apply crossrelease to completion Byungchul Park
2016-06-20  4:55 ` [RFC 07/12] pagemap.h: Remove trailing white space Byungchul Park
2016-06-20  4:55 ` [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock Byungchul Park
2016-06-30 13:04   ` Peter Zijlstra
2016-06-30 23:21     ` Byungchul Park
2016-07-01  8:10       ` Peter Zijlstra
2016-07-01 11:18       ` Kirill A. Shutemov
2016-07-04  4:30         ` Byungchul Park
2016-06-20  4:55 ` [RFC 09/12] cifs/file.c: Remove trailing white space Byungchul Park
2016-06-20  4:55 ` [RFC 10/12] mm/swap_state.c: " Byungchul Park
2016-06-20  4:55 ` [RFC 11/12] lockdep: Call lock_acquire(release) when accessing PG_locked manually Byungchul Park
2016-06-20  4:55 ` [RFC 12/12] x86/dumpstack: Optimize save_stack_trace Byungchul Park
2016-06-20  7:29   ` xinhui
2016-06-20  7:50     ` byungchul.park
2016-06-29 12:43       ` Byungchul Park
2016-06-30 10:38         ` xinhui
2016-06-30 23:06           ` Byungchul Park
2016-06-23 23:37 ` [RFC 00/12] lockdep: Implement crossrelease feature Byungchul Park
2016-06-24  7:08   ` Peter Zijlstra
2016-06-24 11:13     ` Byungchul Park
2016-06-24 11:26   ` Nikolay Borisov
2016-06-27  1:34     ` Byungchul Park
2016-07-01  4:15 ` [PATCH] lockdep: Add a document describing " Byungchul Park
2016-07-01 10:45   ` Peter Zijlstra
2016-07-04  6:42     ` Byungchul Park
2016-07-06  0:49       ` Boqun Feng
2016-07-06  2:17         ` Byungchul Park
2016-07-06  5:33           ` Byungchul Park
2016-07-06  7:56             ` Peter Zijlstra
2016-07-06  8:12               ` Byungchul Park [this message]

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