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 07/12] rwsem: wake queued readers when writer blocks on active read lock
Date: Wed, 12 May 2010 13:33:31 +0100 [thread overview]
Message-ID: <25280.1273667611@redhat.com> (raw)
In-Reply-To: <1273634462-2672-8-git-send-email-walken@google.com>
Michel Lespinasse <walken@google.com> wrote:
> + /* if there are no active locks, wake the front queued process(es) up.
> + *
> + * or if we're called from a failed down_write(), and there were
> + * already threads queued before us, and there are no active writers,
> + * the lock must be read owned; try to wake any read locks that were
> + * queued ahead of us. */
That looks weird. Can I suggest rewriting it thus:
/* If there are no active locks, wake the front queued process(es) up.
*
* Alternatively, if we're called from a failed down_write(), there
* were already threads queued before us and there are no active
* writers, the lock must be read owned; so we try to wake any read
* locks that were queued ahead of us. */
David
next prev parent reply other threads:[~2010-05-12 12:34 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-12 3:20 [PATCH 00/12] rwsem changes + down_read_unfair() proposal Michel Lespinasse
2010-05-12 3:20 ` [PATCH 01/12] rwsem: test for no active locks in __rwsem_do_wake undo code Michel Lespinasse
2010-05-12 3:20 ` [PATCH 02/12] rwsem: use single atomic update for sem count when waking up readers Michel Lespinasse
2010-05-12 3:20 ` [PATCH 03/12] rwsem: let RWSEM_WAITING_BIAS represent any number of waiting threads Michel Lespinasse
2010-05-12 3:20 ` [PATCH 04/12] rwsem: consistently use adjustment variable Michel Lespinasse
2010-05-12 3:20 ` [PATCH 05/12] x86 rwsem: take advantage of new RWSEM_WAITING_BIAS semantics Michel Lespinasse
2010-05-12 3:20 ` [PATCH 06/12] rwsem: wake queued readers when other readers are active Michel Lespinasse
2010-05-12 3:20 ` [PATCH 07/12] rwsem: wake queued readers when writer blocks on active read lock Michel Lespinasse
2010-05-12 3:20 ` [PATCH 08/12] rwsem: smaller wrappers around rwsem_down_failed_common Michel Lespinasse
2010-05-12 3:20 ` [PATCH 09/12] generic rwsem: implement down_read_unfair Michel Lespinasse
2010-05-12 3:21 ` [PATCH 10/12] rwsem: down_read_unfair infrastructure support Michel Lespinasse
2010-05-12 3:21 ` [PATCH 11/12] x86 rwsem: down_read_unfair implementation Michel Lespinasse
2010-05-12 3:21 ` [PATCH 12/12] Use down_read_unfair() for /sys/<pid>/exe and /sys/<pid>/maps files Michel Lespinasse
2010-05-12 22:53 ` KOSAKI Motohiro
2010-05-12 23:35 ` Michel Lespinasse
2010-05-13 0:32 ` KOSAKI Motohiro
2010-05-12 10:39 ` [PATCH 01/12] rwsem: test for no active locks in __rwsem_do_wake undo code David Howells
2010-05-12 11:01 ` [PATCH 02/12] rwsem: use single atomic update for sem count when waking up readers David Howells
2010-05-13 0:54 ` Michel Lespinasse
2010-05-12 11:36 ` David Howells
2010-05-12 11:45 ` [PATCH 04/12] rwsem: consistently use adjustment variable David Howells
2010-05-13 1:12 ` Michel Lespinasse
2010-05-12 12:10 ` [PATCH 05/12] x86 rwsem: take advantage of new RWSEM_WAITING_BIAS semantics David Howells
2010-05-12 12:22 ` [PATCH 06/12] rwsem: wake queued readers when other readers are active David Howells
2010-05-13 2:39 ` Michel Lespinasse
2010-05-13 5:41 ` Michel Lespinasse
2010-05-12 12:33 ` David Howells [this message]
2010-05-12 12:36 ` [PATCH 08/12] rwsem: smaller wrappers around rwsem_down_failed_common David Howells
2010-05-12 12:42 ` David Howells
2010-05-13 2:54 ` Michel Lespinasse
2010-05-12 12:46 ` [PATCH 09/12] generic rwsem: implement down_read_unfair David Howells
2010-05-12 13:08 ` [PATCH 11/12] x86 rwsem: down_read_unfair implementation David Howells
2010-05-12 13:10 ` [PATCH 12/12] Use down_read_unfair() for /sys/<pid>/exe and /sys/<pid>/maps files David Howells
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