From: David Howells <dhowells@redhat.com>
To: Michel Lespinasse <walken@google.com>
Cc: dhowells@redhat.com,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mike Waychison <mikew@google.com>,
Suleiman Souhlal <suleiman@google.com>,
Ying Han <yinghan@google.com>
Subject: Re: [PATCH 09/10] x86 rwsem: down_read_critical implementation
Date: Wed, 19 May 2010 15:36:06 +0100 [thread overview]
Message-ID: <28585.1274279766@redhat.com> (raw)
In-Reply-To: <1274135154-24082-10-git-send-email-walken@google.com>
Michel Lespinasse <walken@google.com> wrote:
> The basic properties that have been true so far still hold:
> - RWSEM_ACTIVE_READ_BIAS & RWSEM_ACTIVE_MASK == 1
> - RWSEM_ACTIVE_WRITE_BIAS & RWSEM_ACTIVE_MASK == 1
> - RWSEM_WAITING_BIAS & RWSEM_ACTIVE_MASK == 0
> - RWSEM_ACTIVE_WRITE_BIAS < 0 and RWSEM_WAITING_BIAS < 0
>
> A new property is introduced: RWSEM_ACTIVE_WRITE_BIAS is set to be
> 'more negative' than RWSEM_WAITING_BIAS. This way, even the first writer
> will set the rwsem count to be < RWSEM_WAITING_BIAS and down_read_critical()
> can make use of this to determine if there are any active writers.
>
> Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: David Howells <dhowells@redhat.com>
next prev parent reply other threads:[~2010-05-19 14:36 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-17 22:25 [PATCH 00/10] V3: rwsem changes + down_read_critical() proposal Michel Lespinasse
2010-05-17 22:25 ` [PATCH 01/10] x86 rwsem: minor cleanups Michel Lespinasse
2010-05-17 22:25 ` [PATCH 02/10] rwsem: fully separate code pathes to wake writers vs readers Michel Lespinasse
2010-05-17 22:25 ` [PATCH 03/10] rwsem: lighter active count checks when waking up readers Michel Lespinasse
2010-05-17 22:25 ` [PATCH 04/10] rwsem: let RWSEM_WAITING_BIAS represent any number of waiting threads Michel Lespinasse
2010-05-17 22:25 ` [PATCH 05/10] rwsem: wake queued readers when writer blocks on active read lock Michel Lespinasse
2010-05-17 22:25 ` [PATCH 06/10] rwsem: smaller wrappers around rwsem_down_failed_common Michel Lespinasse
2010-05-17 22:25 ` [PATCH 07/10] generic rwsem: implement down_read_critical() / up_read_critical() Michel Lespinasse
2010-05-17 22:44 ` Linus Torvalds
2010-05-17 23:13 ` Michel Lespinasse
2010-05-17 23:20 ` Michel Lespinasse
2010-05-19 13:21 ` David Howells
2010-05-19 23:47 ` Michel Lespinasse
2010-05-21 3:35 ` Michel Lespinasse
2010-05-17 22:25 ` [PATCH 08/10] rwsem: down_read_critical infrastructure support Michel Lespinasse
2010-05-17 22:25 ` [PATCH 09/10] x86 rwsem: down_read_critical implementation Michel Lespinasse
2010-05-17 22:25 ` [PATCH 10/10] Use down_read_critical() for /sys/<pid>/exe and /sys/<pid>/maps files Michel Lespinasse
2010-05-19 11:47 ` [PATCH 01/10] x86 rwsem: minor cleanups David Howells
2010-05-20 21:37 ` Michel Lespinasse
2010-05-19 12:04 ` [PATCH 02/10] rwsem: fully separate code pathes to wake writers vs readers David Howells
2010-05-20 21:48 ` Michel Lespinasse
2010-05-19 12:25 ` [PATCH 03/10] rwsem: lighter active count checks when waking up readers David Howells
2010-05-20 22:33 ` Michel Lespinasse
2010-05-21 8:06 ` David Howells
2010-05-19 12:33 ` [PATCH 04/10] rwsem: let RWSEM_WAITING_BIAS represent any number of waiting threads David Howells
2010-05-19 12:44 ` [PATCH 05/10] rwsem: wake queued readers when writer blocks on active read lock David Howells
2010-05-19 12:51 ` [PATCH 06/10] rwsem: smaller wrappers around rwsem_down_failed_common David Howells
2010-05-19 13:34 ` [PATCH 08/10] rwsem: down_read_critical infrastructure support David Howells
2010-05-20 23:30 ` Michel Lespinasse
2010-05-21 8:03 ` David Howells
2010-05-19 14:36 ` David Howells [this message]
2010-05-19 15:21 ` [PATCH 10/10] Use down_read_critical() for /sys/<pid>/exe and /sys/<pid>/maps files David Howells
2010-05-21 2:44 ` Michel Lespinasse
2010-05-22 1:49 ` Michel Lespinasse
2010-05-25 9:42 ` David Howells
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