linux-kernel - Re: SIGSEGV when using "perf record -g" with 3.13-rc* kernel

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Message-ID: <20140110165822.GI7572@laptop.programming.kicks-ass.net>
Date:	Fri, 10 Jan 2014 17:58:22 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Waiman Long <waiman.long@...com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Scott J Norton <scott.norton@...com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: SIGSEGV when using "perf record -g" with 3.13-rc* kernel

On Fri, Jan 10, 2014 at 10:29:13AM -0500, Waiman Long wrote:
> Peter,
> 
> Call Trace:
> <NMI>  [<ffffffff815710af>] dump_stack+0x49/0x62
>  [<ffffffff8104e3bc>] warn_slowpath_common+0x8c/0xc0
>  [<ffffffff8104e40a>] warn_slowpath_null+0x1a/0x20
>  [<ffffffff8105f1f1>] force_sig_info+0x131/0x140
>  [<ffffffff81042a4f>] force_sig_info_fault+0x5f/0x70
>  [<ffffffff8106d8da>] ? search_exception_tables+0x2a/0x50
>  [<ffffffff81043b3d>] ? fixup_exception+0x1d/0x70
>  [<ffffffff81042cc9>] no_context+0x159/0x1f0
>  [<ffffffff81042e8d>] __bad_area_nosemaphore+0x12d/0x230
>  [<ffffffff81042e8d>] ? __bad_area_nosemaphore+0x12d/0x230
>  [<ffffffff81042fa3>] bad_area_nosemaphore+0x13/0x20
>  [<ffffffff81578fc2>] __do_page_fault+0x362/0x480
>  [<ffffffff81578fc2>] ? __do_page_fault+0x362/0x480
>  [<ffffffff815791be>] do_page_fault+0xe/0x10
>  [<ffffffff81575962>] page_fault+0x22/0x30
>  [<ffffffff815817e4>] ? bad_to_user+0x5e/0x66b
>  [<ffffffff81285316>] copy_from_user_nmi+0x76/0x90
>  [<ffffffff81017a20>] perf_callchain_user+0xd0/0x360
>  [<ffffffff8111f64f>] perf_callchain+0x1af/0x1f0
>  [<ffffffff81117693>] perf_prepare_sample+0x2f3/0x3a0
>  [<ffffffff8111a2af>] __perf_event_overflow+0x10f/0x220
>  [<ffffffff8111ab14>] perf_event_overflow+0x14/0x20
>  [<ffffffff8101f69e>] intel_pmu_handle_irq+0x1de/0x3c0
>  [<ffffffff81008e44>] ? emulate_vsyscall+0x144/0x390
>  [<ffffffff81576e64>] perf_event_nmi_handler+0x34/0x60
>  [<ffffffff8157664a>] nmi_handle+0x8a/0x170
>  [<ffffffff81576848>] default_do_nmi+0x68/0x210
>  [<ffffffff81576a80>] do_nmi+0x90/0xe0
>  [<ffffffff81575c67>] end_repeat_nmi+0x1e/0x2e
>  [<ffffffff81008e44>] ? emulate_vsyscall+0x144/0x390
>  [<ffffffff81008e44>] ? emulate_vsyscall+0x144/0x390
>  [<ffffffff81008e44>] ? emulate_vsyscall+0x144/0x390
> <<EOE>>  [<ffffffff81042f7d>] __bad_area_nosemaphore+0x21d/0x230
>  [<ffffffff81042fa3>] bad_area_nosemaphore+0x13/0x20
>  [<ffffffff81578fc2>] __do_page_fault+0x362/0x480
>  [<ffffffff8113cfbc>] ? vm_mmap_pgoff+0xbc/0xe0
>  [<ffffffff815791be>] do_page_fault+0xe/0x10
>  [<ffffffff81575962>] page_fault+0x22/0x30
> ---[ end trace 037bf09d279751ec ]---
> 
> So this is a double page faults. Looking at relevant changes in
> 3.13 kernel, I spotted the following one patch that modified the
> perf_callchain_user() function shown up in the stack trace above:
> 

Hurm, that's an expected double fault, not something we should take the
process down for.

I'll have to look at how all that works for a bit.
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