From: Peter Zijlstra <peterz@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: "Török Edwin" <edwin@clamav.net>, "Ingo Molnar" <mingo@elte.hu>,
"Linux Kernel" <linux-kernel@vger.kernel.org>,
aCaB <acab@clamav.net>, "Nick Piggin" <npiggin@suse.de>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>
Subject: Re: Mutex vs semaphores scheduler bug
Date: Sat, 17 Oct 2009 17:32:07 +0200 [thread overview]
Message-ID: <1255793527.8152.4.camel@laptop> (raw)
In-Reply-To: <24718.1255650266@redhat.com>
On Fri, 2009-10-16 at 00:44 +0100, David Howells wrote:
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > The problem appears to be that rwsem doesn't allow lock-stealing
>
> With good reason. rwsems can be read or write locked for a long time - so if
> readers can jump the queue on read-locked rwsems, then writer starvation is a
> real possibility. I carefully implemented it so that it is a strict FIFO to
> avoid certain problems I was having.
Well, it kinda sucks that rwsem is slower than a mutex.
What about allowing writer stealing when the next contending task is a
writer?
next prev parent reply other threads:[~2009-10-17 15:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-10 14:57 Mutex vs semaphores scheduler bug Török Edwin
2009-10-12 14:53 ` Peter Zijlstra
2009-10-12 15:37 ` Török Edwin
2009-10-15 23:44 ` David Howells
2009-10-17 15:32 ` Peter Zijlstra [this message]
2009-10-20 19:02 ` Török Edwin
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