From: Jan-Simon Pendry <jsp@ms.com>
To: Jakub Jelinek <jj@sunsite.ms.mff.cuni.cz>
Cc: Marcelo Tosatti <marcelo@conectiva.com.br>,
linux-kernel@vger.rutgers.edu
Subject: Re: [PATCH][2.3.0] Read-write locks instead semaphores on UTS structures
Date: Fri, 14 May 1999 15:36:40 +0100 [thread overview]
Message-ID: <373C34F8.5DE45537@ms.com> (raw)
In-Reply-To: 19990514123456.R3172@mff.cuni.cz
Jakub Jelinek wrote
>
> Huh? His patch uses read-write locks and not normal spin-locks, so I don't
> understand what you find wrong on it.
read-write locks are a variant of spin locks. you can deadlock
the system if you go to sleep holding holding any spin lock.
the only exception is the kernel lock which has special code
to deal with it in schedule().
ideally the spinlock code (spin_lock and read_lock et al)
would have debug versions that counted how many locks were
held (in some per-cpu data structure), and have schedule()
check that this number was zero before putting the process
to sleep.
jan-simon.
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prev parent reply other threads:[~1999-05-15 4:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-05-12 19:50 [PATCH][2.3.0] Read-write locks instead semaphores on UTS structures Marcelo Tosatti
[not found] ` <373B07EF.58664F9B@ms.com>
1999-05-14 10:34 ` Jakub Jelinek
1999-05-14 14:36 ` Jan-Simon Pendry [this message]
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