From: Andi Kleen <andi@firstfloor.org>
To: paulmck@linux.vnet.ibm.com
Cc: Nick Piggin <npiggin@suse.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [rfc] "fair" rw spinlocks
Date: Sat, 28 Nov 2009 12:15:07 +0100 [thread overview]
Message-ID: <87pr72529w.fsf@basil.nowhere.org> (raw)
In-Reply-To: <20091128020739.GA18149@linux.vnet.ibm.com> (Paul E. McKenney's message of "Fri, 27 Nov 2009 18:07:39 -0800")
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
>
> The usual trick would be to keep per-fair-rwlock state in per-CPU
> variables. If it is forbidden to read-acquire one nestable fair rwlock
> while read-holding another, then this per-CPU state can be a single
> pointer and a nesting count. On the other hand, if it is permitted to
> read-acquire one nestable fair rwlock while holding another, then one
> can use a small per-CPU array of pointer/count pairs.
The problem is that in preemptible kernels kernel threads can switch
CPUs all the time. How would you sync the per CPU state then?
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2009-11-28 11:15 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-23 14:54 [rfc] "fair" rw spinlocks Nick Piggin
2009-11-24 20:19 ` David Miller
2009-11-25 6:52 ` Nick Piggin
2009-11-25 8:49 ` Andi Kleen
2009-11-25 8:56 ` Nick Piggin
2009-11-24 20:47 ` Andi Kleen
2009-11-25 6:54 ` Nick Piggin
2009-11-25 8:48 ` Andi Kleen
2009-11-25 13:09 ` Arnd Bergmann
2009-11-28 2:07 ` Paul E. McKenney
2009-11-28 11:15 ` Andi Kleen [this message]
2009-11-28 15:20 ` Paul E. McKenney
2009-11-28 17:30 ` Linus Torvalds
2009-11-29 18:51 ` Paul E. McKenney
2009-11-30 7:57 ` Nick Piggin
2009-11-30 7:55 ` Nick Piggin
2009-11-30 15:22 ` Linus Torvalds
2009-11-30 15:40 ` Nick Piggin
2009-11-30 16:07 ` Linus Torvalds
2009-11-30 16:17 ` Nick Piggin
2009-11-30 16:39 ` Paul E. McKenney
2009-11-30 17:05 ` Linus Torvalds
2009-11-30 17:13 ` Nick Piggin
2009-11-30 17:18 ` Linus Torvalds
2009-12-01 17:03 ` Arnd Bergmann
2009-12-01 17:15 ` Linus Torvalds
2009-11-30 18:29 ` Paul E. McKenney
2009-11-30 16:20 ` Paul E. McKenney
2009-11-30 10:00 ` Christoph Hellwig
2009-11-30 15:52 ` Linus Torvalds
2009-11-30 17:46 ` Ingo Molnar
2009-11-30 21:12 ` Thomas Gleixner
2009-11-30 21:27 ` Peter Zijlstra
2009-11-30 22:02 ` Thomas Gleixner
2009-11-30 22:11 ` Linus Torvalds
2009-11-30 22:37 ` Thomas Gleixner
2009-11-30 22:49 ` Linus Torvalds
2009-12-01 17:37 ` [PATCH] audit: Call tty_audit_push_task() outside preempt disabled region Thomas Gleixner
2009-12-01 18:22 ` Oleg Nesterov
2009-12-01 19:53 ` Thomas Gleixner
2009-12-06 3:12 ` [rfc] "fair" rw spinlocks Eric W. Biederman
2009-12-07 18:18 ` Paul E. McKenney
2009-12-07 22:24 ` Eric W. Biederman
2009-12-07 22:35 ` Andi Kleen
2009-12-07 23:19 ` Eric W. Biederman
2009-12-08 1:39 ` Paul E. McKenney
2009-12-08 2:11 ` Eric W. Biederman
2009-12-08 2:37 ` Paul E. McKenney
2009-12-07 18:32 ` Oleg Nesterov
2009-12-07 20:38 ` Peter Zijlstra
2009-12-09 15:55 ` Oleg Nesterov
2009-12-07 22:10 ` Eric W. Biederman
2009-12-09 15:37 ` Oleg Nesterov
2009-12-10 3:36 ` Eric W. Biederman
2009-12-10 6:22 ` Paul E. McKenney
2009-12-10 10:31 ` Eric W. Biederman
2009-12-10 16:41 ` Paul E. McKenney
2009-12-01 19:01 ` Mathieu Desnoyers
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