From: Robert Love <rml@tech9.net>
To: Zwane Mwaikambo <zwane@linuxpower.ca>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PATCH] small fixes in brlock.h
Date: 09 Mar 2003 19:10:24 -0500 [thread overview]
Message-ID: <1047255023.680.16.camel@phantasy.awol.org> (raw)
In-Reply-To: <Pine.LNX.4.50.0303091901370.1464-100000@montezuma.mastecende.com>
On Sun, 2003-03-09 at 19:03, Zwane Mwaikambo wrote:
> > cpu = smp_processor_id();
> > /* do not want to preempt here, but we can! */
> > preempt_disable();
> > _raw_read_lock(&__brlock_array[cpu][idx]);
>
> How are we able to preempt there? Timer tick?
Yep. Any interrupt, actually.
Or the reschedule IPI on SMP systems.
Kernel preemption off an interrupt is actually the most common (and the
ideal) place to preempt since an interrupt is usually what wakes up a
task off I/O and sets need_resched. So kernel preemption lets us
reschedule the higher priority task the moment the interrupt wakes it
up. Of course, if a lock is held, we have to wait till we drop it.
Robert Love
next prev parent reply other threads:[~2003-03-09 23:59 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-03-09 23:44 Zwane Mwaikambo
2003-03-10 0:00 ` Robert Love
2003-03-10 0:03 ` Zwane Mwaikambo
2003-03-10 0:10 ` Robert Love [this message]
2003-03-10 1:11 ` Zwane Mwaikambo
2003-03-10 0:15 ` Robert Love
2003-03-10 2:33 ` Linus Torvalds
2003-03-10 21:54 ` Roman Zippel
2003-03-12 0:13 ` [PATCH] (0/8) replace brlock with RCU Stephen Hemminger
2003-03-12 0:23 ` Linus Torvalds
2003-03-12 0:28 ` David S. Miller
2003-03-12 1:36 ` Roman Zippel
2003-03-12 0:14 ` [PATCH] (1/8) Eliminate brlock in psnap Stephen Hemminger
2003-03-12 1:03 ` Roman Zippel
2003-03-12 1:13 ` Zwane Mwaikambo
2003-03-12 0:14 ` [PATCH] (2/8) Eliminate brlock for packet_type Stephen Hemminger
2003-03-12 0:20 ` David S. Miller
2003-03-12 0:25 ` Stephen Hemminger
2003-03-12 0:14 ` [PATCH] (3/8) Eliminate brlock from vlan Stephen Hemminger
2003-03-12 0:14 ` [PATCH] (4/8) Eliminate brlock in net/bridge Stephen Hemminger
2003-03-12 0:14 ` [PATCH] (5/8) Eliminate brlock from netfilter Stephen Hemminger
2003-03-12 1:25 ` Zwane Mwaikambo
2003-03-12 0:15 ` [PATCH] (6/8) Eliminate brlock from ipv4 Stephen Hemminger
2003-03-12 0:15 ` [PATCH] (7/8) Eliminate brlock from IPV6 Stephen Hemminger
2003-03-12 0:15 ` [PATCH] (8/8) Kill brlock Stephen Hemminger
2003-03-12 0:23 ` David S. Miller
2003-03-12 0:31 ` Stephen Hemminger
2003-03-12 0:34 ` David S. Miller
2003-03-12 0:44 ` Linus Torvalds
2003-03-12 0:48 ` Stephen Hemminger
2003-03-12 2:31 ` Alan Cox
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