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From: Matthew Wilcox <willy@infradead.org>
To: "byungchul.park" <byungchul.park@lge.com>
Cc: "'Peter Zijlstra'" <peterz@infradead.org>,
	mingo@kernel.org, tglx@linutronix.de, walken@google.com,
	boqun.feng@gmail.com, kirill@shutemov.name,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	iamjoonsoo.kim@lge.com, akpm@linux-foundation.org,
	npiggin@gmail.com, kernel-team@lge.com
Subject: Re: [PATCH v5 06/13] lockdep: Implement crossrelease feature
Date: Thu, 2 Mar 2017 06:39:49 -0800	[thread overview]
Message-ID: <20170302143949.GP16328@bombadil.infradead.org> (raw)
In-Reply-To: <004101d2930f$d51a9f90$7f4fdeb0$@lge.com>

On Thu, Mar 02, 2017 at 01:45:35PM +0900, byungchul.park wrote:
> From: Matthew Wilcox [mailto:willy@infradead.org]
> > On Tue, Feb 28, 2017 at 07:15:47PM +0100, Peter Zijlstra wrote:
> > > (And we should not be returning to userspace with locks held anyway --
> > > lockdep already has a check for that).
> > 
> > Don't we return to userspace with page locks held, eg during async
> > directio?
> 
> Hello,
> 
> I think that the check when returning to user with crosslocks held
> should be an exception. Don't you think so?

Oh yes.  We have to keep the pages locked during reads, and we have to
return to userspace before I/O is complete, therefore we have to return
to userspace with pages locked.  They'll be unlocked by the interrupt
handler in page_endio().

Speaking of which ... this feature is far too heavy for use in production
on pages.  You're almost trebling the size of struct page.  Can we
do something like make all struct pages share the same lockdep_map?
We'd have to not complain about holding one crossdep lock and acquiring
another one of the same type, but with millions of pages in the system,
it must surely be creating a gargantuan graph right now?

  reply	other threads:[~2017-03-02 14:40 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-18 13:17 [PATCH v5 00/13] lockdep: Implement crossrelease feature Byungchul Park
2017-01-18 13:17 ` [PATCH v5 01/13] lockdep: Refactor lookup_chain_cache() Byungchul Park
2017-01-19  9:16   ` Boqun Feng
2017-01-19  9:52     ` Byungchul Park
2017-01-26  7:53     ` Byungchul Park
2017-01-18 13:17 ` [PATCH v5 02/13] lockdep: Fix wrong condition to print bug msgs for MAX_LOCKDEP_CHAIN_HLOCKS Byungchul Park
2017-01-18 13:17 ` [PATCH v5 03/13] lockdep: Add a function building a chain between two classes Byungchul Park
2017-01-18 13:17 ` [PATCH v5 04/13] lockdep: Refactor save_trace() Byungchul Park
2017-01-18 13:17 ` [PATCH v5 05/13] lockdep: Pass a callback arg to check_prev_add() to handle stack_trace Byungchul Park
2017-01-26  7:43   ` Byungchul Park
2017-01-18 13:17 ` [PATCH v5 06/13] lockdep: Implement crossrelease feature Byungchul Park
2017-02-28 12:26   ` Peter Zijlstra
2017-02-28 12:45   ` Peter Zijlstra
2017-02-28 12:49     ` Peter Zijlstra
2017-03-01  6:20       ` Byungchul Park
2017-02-28 13:05   ` Peter Zijlstra
2017-02-28 13:28     ` Byungchul Park
2017-02-28 13:35       ` Peter Zijlstra
2017-02-28 14:00         ` Byungchul Park
2017-02-28 13:10   ` Peter Zijlstra
2017-02-28 13:24     ` Byungchul Park
2017-02-28 18:29       ` Peter Zijlstra
2017-03-01  4:40         ` Byungchul Park
2017-03-01 10:45           ` Peter Zijlstra
2017-03-01 12:10             ` Byungchul Park
2017-02-28 13:40   ` Peter Zijlstra
2017-03-01  5:43     ` Byungchul Park
2017-03-01 12:28       ` Peter Zijlstra
2017-03-02 13:40         ` Peter Zijlstra
2017-03-03  0:17           ` Byungchul Park
2017-03-03  8:14             ` Peter Zijlstra
2017-03-03  9:13               ` Peter Zijlstra
2017-03-03  9:32                 ` Peter Zijlstra
2017-03-05  3:33                 ` Byungchul Park
2017-08-10 12:18                 ` [tip:locking/core] locking/lockdep: Avoid creating redundant links tip-bot for Peter Zijlstra
2017-03-05  3:08               ` [PATCH v5 06/13] lockdep: Implement crossrelease feature Byungchul Park
2017-03-07 11:42                 ` Peter Zijlstra
2017-03-03  0:39           ` Byungchul Park
2017-02-28 15:49   ` Peter Zijlstra
2017-03-01  5:17     ` Byungchul Park
2017-03-01  6:18       ` Byungchul Park
2017-03-02  2:52       ` Byungchul Park
2017-02-28 18:15   ` Peter Zijlstra
2017-03-01  7:21     ` Byungchul Park
2017-03-01 10:43       ` Peter Zijlstra
2017-03-01 12:27         ` Byungchul Park
2017-03-02  4:20     ` Matthew Wilcox
2017-03-02  4:45       ` byungchul.park
2017-03-02 14:39         ` Matthew Wilcox [this message]
2017-03-02 23:50           ` Byungchul Park
2017-03-05  8:01             ` Byungchul Park
2017-03-14  7:36     ` Byungchul Park
2017-03-02 13:41   ` Peter Zijlstra
2017-03-02 23:43     ` Byungchul Park
2017-01-18 13:17 ` [PATCH v5 07/13] lockdep: Make print_circular_bug() aware of crossrelease Byungchul Park
2017-01-18 13:17 ` [PATCH v5 08/13] lockdep: Apply crossrelease to completions Byungchul Park
2017-01-18 13:17 ` [PATCH v5 09/13] pagemap.h: Remove trailing white space Byungchul Park
2017-01-18 13:17 ` [PATCH v5 10/13] lockdep: Apply crossrelease to PG_locked locks Byungchul Park
2017-01-18 13:17 ` [PATCH v5 11/13] lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked Byungchul Park
2017-01-18 13:17 ` [PATCH v5 12/13] lockdep: Move data of CONFIG_LOCKDEP_PAGELOCK from page to page_ext Byungchul Park
2017-01-18 13:17 ` [PATCH v5 13/13] lockdep: Crossrelease feature documentation Byungchul Park
2017-01-20  9:08   ` [REVISED DOCUMENT] " Byungchul Park
2017-02-20  8:38 ` [PATCH v5 00/13] lockdep: Implement crossrelease feature Byungchul Park

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