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 14:51:11 +0200 [thread overview]
Message-ID: <20131016125111.GB2611@gmail.com> (raw)
In-Reply-To: <20131016084219.53deac7a@gandalf.local.home>
* Steven Rostedt <rostedt@goodmis.org> wrote:
> On Wed, 16 Oct 2013 08:11:18 +0200
> Ingo Molnar <mingo@kernel.org> wrote:
>
> >
> > * 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.
>
> Sure, want me to add this to the change log?
Yeah, that would be helpful - but only the stack trace portion I suspect,
to make it clear what caused the fault.
The one posted in the thread shows:
[ 17.148755] [<c2825b08>] do_page_fault+0x8/0x10
[ 17.153926] [<c2823066>] error_code+0x5a/0x60
[ 17.158905] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 17.164760] [<c208d1a9>] ? module_address_lookup+0x29/0xb0
[ 17.170999] [<c208dddb>] kallsyms_lookup+0x9b/0xb0
[ 17.186804] [<c208def4>] sprint_symbol+0x14/0x20
[ 17.192063] [<c208df1e>] __print_symbol+0x1e/0x40
[ 17.197430] [<c25e00d7>] ? ashmem_shrink+0x77/0xf0
[ 17.202895] [<c25e13e0>] ? logger_aio_write+0x230/0x230
[ 17.208845] [<c205bdf5>] ? up+0x25/0x40
[ 17.213242] [<c2039cb7>] ? console_unlock+0x337/0x440
[ 17.218998] [<c2818236>] ? printk+0x38/0x3a
[ 17.223782] [<c20006d0>] __show_regs+0x70/0x190
[ 17.228954] [<c200353a>] show_regs+0x3a/0x1b0
[ 17.233931] [<c2818236>] ? printk+0x38/0x3a
[ 17.238717] [<c2824182>] arch_trigger_all_cpu_backtrace_handler+0x62/0x80
[ 17.246413] [<c2823919>] nmi_handle.isra.0+0x39/0x60
[ 17.252071] [<c2823a29>] do_nmi+0xe9/0x3f0
So kallsyms_lookup() faulted, while the NMI watchdog triggered a
show_regs()? How is that possible?
Thanks,
Ingo
next prev parent reply other threads:[~2013-10-16 12:51 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
2013-10-16 12:42 ` Steven Rostedt
2013-10-16 12:51 ` Ingo Molnar [this message]
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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