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From: Ingo Molnar <mingo@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@linux.intel.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"paulmck@linux.vnet.ibm.com" <paulmck@linux.vnet.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"Wang, Xiaoming" <xiaoming.wang@intel.com>,
	"Li, Zhuangzhi" <zhuangzhi.li@intel.com>,
	"Liu, Chuansheng" <chuansheng.liu@intel.com>
Subject: Re: [PATCH] x86: Remove WARN_ON(in_nmi()) from vmalloc_fault
Date: Wed, 16 Oct 2013 08:11:18 +0200	[thread overview]
Message-ID: <20131016061118.GA21109@gmail.com> (raw)
In-Reply-To: <20131015163906.342d8ffa@gandalf.local.home>


* Steven Rostedt <rostedt@goodmis.org> wrote:

> Since the NMI iretq nesting has been fixed, there's no reason that
> an NMI handler can not take a page fault for vmalloc'd code. No locks
> are taken in that code path, and the software now handles nested NMIs
> when the fault re-enables NMIs on iretq.
> 
> Not only that, if the vmalloc_fault() WARN_ON_ONCE() is hit, and that
> warn on triggers a vmalloc fault for some reason, then we can go into
> an infinite loop (the WARN_ON_ONCE() does the WARN() before updating
> the variable to make it happen "once").
> 
> Reported-by: "Liu, Chuansheng" <chuansheng.liu@intel.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Would be nice to see the warning quoted that triggered this.

Thanks,

	Ingo

  reply	other threads:[~2013-10-16  6:11 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-10-15 20:39 [PATCH] x86: Remove WARN_ON(in_nmi()) from vmalloc_fault Steven Rostedt
2013-10-16  6:11 ` Ingo Molnar [this message]
2013-10-16 12:42   ` Steven Rostedt
2013-10-16 12:51     ` Ingo Molnar
2013-10-16 13:01       ` Borislav Petkov
2013-10-16 13:03       ` Steven Rostedt
2013-10-17  0:29       ` Liu, Chuansheng
2013-10-16 11:40 ` Frederic Weisbecker
2013-10-16 12:45   ` Steven Rostedt
2013-10-16 13:08     ` Frederic Weisbecker
2013-10-16 13:14       ` Steven Rostedt
2013-10-16 13:28         ` Frederic Weisbecker
2013-10-16 13:37           ` Steven Rostedt
2013-10-16 19:39             ` Paul E. McKenney
2013-10-16 19:36       ` Paul E. McKenney
2013-10-16 19:57         ` Steven Rostedt
2013-10-18 11:54           ` Paul E. McKenney
2013-10-17 13:59         ` Frederic Weisbecker

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