From: Ingo Molnar <mingo@elte.hu>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
efault@gmx.de, Arne Jansen <lists@die-jansens.de>
Subject: Re: [PATCH 3/3] printk: Avoid all wakeups from printk
Date: Thu, 9 Jun 2011 16:19:59 +0200 [thread overview]
Message-ID: <20110609141959.GF21100@elte.hu> (raw)
In-Reply-To: <1307628393.3941.87.camel@twins>
* Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> On Thu, 2011-06-09 at 15:55 +0200, Ingo Molnar wrote:
>
> > > @@ -943,19 +939,14 @@ asmlinkage int vprintk(const char *fmt,
> > > if (*p == '\n')
> > > new_text_line = 1;
> > > }
> > > + printk_cpu = UINT_MAX;
> > > + spin_unlock(&logbuf_lock);
> >
> > Hm, is that printk_cpu setting inside the critical section safe? What
> > happens if we get an NMI on this CPU in that window?
>
> That's what the old code did, also NMI really shouldn't printk(), but
> yeah, can flip those two lines, but in that same vein I should also flip
> the setting of that variable with acquiring the lock.
Flipping it won't be enough - we could override another CPU's
protection ...
Thanks,
Ingo
next prev parent reply other threads:[~2011-06-09 14:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-09 13:06 [PATCH 0/3] printk: Remove lockdep_off() and wakeups Peter Zijlstra
2011-06-09 13:06 ` [PATCH 1/3] printk: Release console_sem after logbuf_lock Peter Zijlstra
2011-06-09 20:06 ` Andrew Morton
2011-06-09 20:27 ` Ingo Molnar
2011-06-09 20:54 ` Peter Zijlstra
2011-06-09 21:07 ` Andrew Morton
2011-06-09 23:57 ` Hugh Dickins
2011-06-10 0:08 ` Andrew Morton
2011-06-10 9:33 ` Ingo Molnar
2011-06-10 9:40 ` Peter Zijlstra
2011-06-10 9:42 ` Peter Zijlstra
2011-06-10 11:28 ` Peter Zijlstra
2011-06-10 12:30 ` Peter Zijlstra
2011-06-10 12:34 ` Ingo Molnar
2011-06-10 12:41 ` Peter Zijlstra
2011-06-10 12:42 ` Peter Zijlstra
2011-06-23 19:03 ` Pavel Machek
2011-06-10 9:30 ` Ingo Molnar
2011-06-10 10:15 ` Peter Zijlstra
2011-06-09 13:06 ` [PATCH 2/3] printk, lockdep: Remove lockdep_off() usage Peter Zijlstra
2011-06-10 13:23 ` Peter Zijlstra
2011-06-09 13:06 ` [PATCH 3/3] printk: Avoid all wakeups from printk Peter Zijlstra
2011-06-09 13:32 ` Ingo Molnar
2011-06-09 13:40 ` Peter Zijlstra
2011-06-09 13:55 ` Ingo Molnar
2011-06-09 14:06 ` Peter Zijlstra
2011-06-09 14:19 ` Ingo Molnar [this message]
2011-06-09 14:23 ` Peter Zijlstra
2011-06-09 15:47 ` Linus Torvalds
2011-06-09 15:51 ` Ingo Molnar
2011-06-09 16:25 ` Peter Zijlstra
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