From: Ingo Molnar <mingo@elte.hu>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
lkml <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>,
Arjan van de Ven <arjan@infradead.org>,
Nicolas Pitre <nico@cam.org>,
Jes Sorensen <jes@trained-monkey.org>,
Al Viro <viro@ftp.linux.org.uk>, Oleg Nesterov <oleg@tv-sign.ru>,
David Howells <dhowells@redhat.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Christoph Hellwig <hch@infradead.org>, Andi Kleen <ak@suse.de>,
Russell King <rmk+lkml@arm.linux.org.uk>
Subject: Re: [patch 08/19] mutex subsystem, core
Date: Tue, 3 Jan 2006 16:42:44 +0100 [thread overview]
Message-ID: <20060103154244.GA6884@elte.hu> (raw)
In-Reply-To: <Pine.LNX.4.64.0601030736531.3668@g5.osdl.org>
* Linus Torvalds <torvalds@osdl.org> wrote:
> On Tue, 3 Jan 2006, Ingo Molnar wrote:
> > >
> > > Is this an interrupt deadlock, or do you not allow interrupt contexts
> > > to even trylock a mutex?
> >
> > correct, no irq contexts are allowed. This is also checked for if
> > CONFIG_DEBUG_MUTEXES is enabled.
>
> Note that semaphores are definitely used from interrupt context, and
> as such you can't replace them with mutexes if you do this.
>
> The prime example is the console semaphore. See kernel/printk.c, look
> for "down_trylock()", and realize that they are all about interrupts.
yeah, i know - and i'm not trying to replace _all_ semaphore uses.
down_trylock() is used only 54 times in drivers/*, while down() is used
2986 times. And even of those 54 cases, only a small minority does it
from an IRQ context.
Ingo
next prev parent reply other threads:[~2006-01-03 15:43 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-03 10:08 [patch 08/19] mutex subsystem, core Ingo Molnar
2006-01-03 13:15 ` Nick Piggin
2006-01-03 15:05 ` Ingo Molnar
2006-01-03 15:38 ` Linus Torvalds
2006-01-03 15:42 ` Ingo Molnar [this message]
2006-01-03 18:00 ` Oleg Nesterov
2006-01-03 16:49 ` Ingo Molnar
-- strict thread matches above, loose matches on Subject: below --
2006-01-03 16:46 Ingo Molnar
2006-01-03 15:58 Kai Geek
2006-01-02 16:34 Ingo Molnar
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