From: Steven Rostedt <rostedt@goodmis.org>
To: Christoph Lameter <cl@gentwo.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Christoph Lameter <cl@linux.com>
Subject: Re: [RFC][PATCH 4/5] printk: Have wake_up_klogd() use __this_cpu_write()
Date: Mon, 19 Sep 2011 19:33:28 -0400 [thread overview]
Message-ID: <1316475208.29966.2.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1109191653460.19059@router.home>
On Mon, 2011-09-19 at 16:54 -0500, Christoph Lameter wrote:
> On Mon, 19 Sep 2011, Steven Rostedt wrote:
>
> > From: Steven Rostedt <srostedt@redhat.com>
> >
> > The wake up code that triggers klogd does not really matter which
> > CPU it enables the wake up on. Every CPU will be doing a printk_tick()
> > and check the current CPU. As long as one of the CPUs triggers the
> > wakeup we are fine. Use __this_cpu_write() instead of this_cpu_write()
> > to show that we do not care.
>
> printk_needs_cpu() is always called from context where we have disabled
> interrupts therefore this is safe to do.
hehe, the patch is deceiving ;)
@@ -1225,7 +1225,7 @@ int printk_needs_cpu(int cpu)
void wake_up_klogd(void)
{
if (waitqueue_active(&log_wait))
The printk_needs_cpu may be in the patch header there, but the real
function name happened to be in the call itself. "wake_up_klogd()".
Note, just because something is always in a location that preemption is
disabled, does not mean it should use the __this_cpu*() variants.
Because if things change, it may become a problem later on.
-- Steve
>
> Reviewed-by: Christoph Lameter <cl@gentwo.org>
next prev parent reply other threads:[~2011-09-19 23:33 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-19 21:20 [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write() Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 1/5] x86: Remove const_udelay() caring about which cpu var it uses Steven Rostedt
2011-09-19 21:51 ` Christoph Lameter
2011-09-19 23:31 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 2/5] mm: Switch mod_state() to __this_cpu_read() Steven Rostedt
2011-09-19 22:02 ` Christoph Lameter
2011-09-19 23:48 ` Steven Rostedt
2011-09-20 14:46 ` Christoph Lameter
2011-09-20 15:16 ` Steven Rostedt
2011-09-20 15:54 ` Christoph Lameter
2011-09-20 16:07 ` Steven Rostedt
2011-09-20 22:19 ` Valdis.Kletnieks
2011-09-20 13:49 ` Thomas Gleixner
2011-09-20 14:01 ` Steven Rostedt
2011-09-20 14:51 ` Christoph Lameter
2011-09-20 15:11 ` Steven Rostedt
2011-09-20 15:59 ` Christoph Lameter
2011-09-20 16:03 ` Steven Rostedt
2011-09-20 16:07 ` Christoph Lameter
2011-09-20 15:27 ` Thomas Gleixner
2011-09-20 16:02 ` Christoph Lameter
2011-09-20 16:51 ` Thomas Gleixner
2011-09-20 17:08 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 3/5] memcg: Disable preemption in memcg_check_events() Steven Rostedt
2011-09-20 14:20 ` Johannes Weiner
2011-09-20 14:24 ` Johannes Weiner
2011-09-20 14:33 ` Steven Rostedt
2011-09-24 0:46 ` Steven Rostedt
2011-09-19 21:20 ` [RFC][PATCH 4/5] printk: Have wake_up_klogd() use __this_cpu_write() Steven Rostedt
2011-09-19 21:54 ` Christoph Lameter
2011-09-19 23:33 ` Steven Rostedt [this message]
2011-09-20 14:54 ` Christoph Lameter
2011-09-20 14:55 ` Peter Zijlstra
2011-09-19 21:20 ` [RFC][PATCH 5/5] percpu: Add preempt checks back into this_cpu_read/write() Steven Rostedt
2011-09-19 21:49 ` [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write() Christoph Lameter
2011-09-20 3:06 ` Steven Rostedt
2011-09-20 12:44 ` Valdis.Kletnieks
2011-09-20 13:51 ` Thomas Gleixner
2011-09-20 14:58 ` Christoph Lameter
2011-09-20 15:17 ` Steven Rostedt
2011-09-20 14:57 ` Christoph Lameter
2011-09-20 15:19 ` Steven Rostedt
2011-09-20 16:08 ` Christoph Lameter
2011-09-20 16:31 ` Steven Rostedt
2011-09-20 16:56 ` Steven Rostedt
2011-09-20 17:09 ` Peter Zijlstra
2011-09-20 17:15 ` Steven Rostedt
2011-09-20 17:25 ` Mathieu Desnoyers
2011-09-20 18:03 ` Steven Rostedt
2011-09-20 18:12 ` Mathieu Desnoyers
2011-09-20 18:27 ` Steven Rostedt
2011-09-20 18:34 ` Mathieu Desnoyers
2011-09-20 22:32 ` Valdis.Kletnieks
2011-09-20 22:17 ` Valdis.Kletnieks
2011-09-21 1:33 ` Steven Rostedt
2011-09-20 15:46 ` Mathieu Desnoyers
2011-09-20 16:00 ` Steven Rostedt
2011-09-20 16:10 ` Christoph Lameter
2011-09-20 16:50 ` Peter Zijlstra
2011-09-20 18:54 ` Steven Rostedt
2011-09-21 15:16 ` Christoph Lameter
2011-09-21 15:31 ` Steven Rostedt
2011-09-21 15:59 ` Christoph Lameter
2011-09-21 16:12 ` Steven Rostedt
2011-09-21 16:32 ` Thomas Gleixner
2011-09-20 2:20 ` Andi Kleen
2011-09-20 3:12 ` Steven Rostedt
2011-09-20 3:17 ` Steven Rostedt
2011-09-20 8:32 ` Thomas Gleixner
2011-09-20 12:10 ` Steven Rostedt
2011-09-20 15:03 ` Christoph Lameter
2011-09-20 15:07 ` Peter Zijlstra
2011-09-20 16:05 ` Christoph Lameter
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