From: Arjan van de Ven <arjan@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
torvalds@osdl.org, akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: R/W semaphore changes
Date: Tue, 04 Jul 2006 14:52:42 +0200 [thread overview]
Message-ID: <1152017562.3109.48.camel@laptopd505.fenrus.org> (raw)
In-Reply-To: <14683.1152017262@warthog.cambridge.redhat.com>
On Tue, 2006-07-04 at 13:47 +0100, David Howells wrote:
> I see you've made some R/W semaphore changes...
>
> | /*
> | * nested locking:
> | */
>
> This comment is inadequate. Please be more explicit about when you're allowed
> to do this.
>
> | extern void down_read_nested(struct rw_semaphore *sem, int subclass);
> | extern void down_write_nested(struct rw_semaphore *sem, int subclass);
>
> Please, please, please don't. R/W semaphores are _not_ permitted to nest.
yet they do in places, there where there is a natural hierarchy..
> | # define down_read_nested(sem, subclass) down_read(sem)
> | # define down_write_nested(sem, subclass) down_write(sem)
>
> This is _not_ okay.
why not?
next prev parent reply other threads:[~2006-07-04 12:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-04 12:47 David Howells
2006-07-04 12:52 ` Arjan van de Ven [this message]
2006-07-04 13:05 ` David Howells
2006-07-04 13:17 ` Arjan van de Ven
2006-07-04 13:21 ` Ingo Molnar
2006-07-04 13:33 ` [patch] lockdep: add more rwsem.h documentation Ingo Molnar
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