From: Nikita Danilov <nikita@clusterfs.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-ID: <17313.29296.170999.539035@gargle.gargle.HOWL>
Date: Thu, 15 Dec 2005 16:41:04 +0300
To: Andrew Morton <akpm@osdl.org>
Cc: tglx@linutronix.de, dhowells@redhat.com, alan@lxorguk.ukuu.org.uk,
       pj@sgi.com, mingo@elte.hu, hch@infradead.org, torvalds@osdl.org,
       arjan@infradead.org, matthew@wil.cx, linux-kernel@vger.kernel.org,
       linux-arch@vger.kernel.org
Subject: Re: [PATCH 1/19] MUTEX: Introduce simple mutex implementation
Newsgroups: gmane.linux.kernel
In-Reply-To: <20051214155432.320f2950.akpm@osdl.org>
References: <1134559121.25663.14.camel@localhost.localdomain>
	<13820.1134558138@warthog.cambridge.redhat.com>
	<20051213143147.d2a57fb3.pj@sgi.com>
	<20051213094053.33284360.pj@sgi.com>
	<dhowells1134431145@warthog.cambridge.redhat.com>
	<20051212161944.3185a3f9.akpm@osdl.org>
	<20051213075441.GB6765@elte.hu>
	<20051213090219.GA27857@infradead.org>
	<20051213093949.GC26097@elte.hu>
	<20051213100015.GA32194@elte.hu>
	<6281.1134498864@warthog.cambridge.redhat.com>
	<14242.1134558772@warthog.cambridge.redhat.com>
	<16315.1134563707@warthog.cambridge.redhat.com>
	<1134568731.4275.4.camel@tglx.tec.linutronix.de>
	<43A0AD54.6050109@rtr.ca>
	<20051214155432.320f2950.akpm@osdl.org>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1305
Lines: 41

Andrew Morton writes:
 > Mark Lord <lkml@rtr.ca> wrote:
 > >
 > > Leaving up()/down() as-is is really the most sensible option.
 > >
 > 
 > Absolutely.
 > 
 > I must say that my interest in this stuff is down in
 > needs-an-electron-microscope-to-locate territory.  down() and up() work
 > just fine and they're small, efficient, well-debugged and well-understood. 
 > We need a damn good reason for taking on tree-wide churn or incompatible
 > renames or addition of risk.  What's the damn good reason here?
 > 
 > Please.  Go fix some bugs.  We're not short of them.

But this change is about fixing bugs: mutex assumes that

 - only owner can unlock, and

 - owner cannot lock (immediate self-deadlock).

This can be checked by the debugging code, and yes, these kinds of
errors do happen.

Not to say that by looking at

        struct foo_bar_baz {
                struct mutex fbb_mutex;
                ...
        };

one can instantly infer that ->fbb_mutex is used to serialize something
rather than serves as some fancy signaling mechanism.

Nikita.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/