linux-kernel - Re: [PATCH v2 0/6] Function tracing support for pstore

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Message-ID: <20120615212824.GA23338@kroah.com>
Date:	Fri, 15 Jun 2012 14:28:24 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Anton Vorontsov <anton.vorontsov@...aro.org>
Cc:	Kees Cook <keescook@...omium.org>,
	Colin Cross <ccross@...roid.com>,
	Tony Luck <tony.luck@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, devel@...verdev.osuosl.org,
	linaro-kernel@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
	patches@...aro.org, Marco Stornelli <marco.stornelli@...il.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-kernel@...r.kernel.org, arve@...roid.com,
	Jesper Juhl <jj@...osbits.net>,
	John Stultz <john.stultz@...aro.org>,
	Shuah Khan <shuahkhan@...il.com>,
	Rebecca Schultz Zavin <rebecca@...roid.com>,
	WANG Cong <xiyou.wangcong@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	kernel-team@...roid.com, Thomas Meyer <thomas@...3r.de>
Subject: Re: [PATCH v2 0/6] Function tracing support for pstore

On Fri, Jun 15, 2012 at 10:07:00AM -0700, Anton Vorontsov wrote:
> Hi all,
> 
> In v2:
> - Do not introduce a separate 'persistent' tracer, but introduce an
>   option to the existing 'function' tracer.
> 
> Rationale for this patch set:
> 
> With this support kernel can save functions call chain log into a
> persistent ram buffer that can be decoded and dumped after reboot
> through pstore filesystem. It can be used to determine what function
> was last called before a hang or an unexpected reset (caused by, for
> example, a buggy driver that abuses HW).
> 
> Here's a "nano howto", to get the idea:
> 
>  # mount -t debugfs debugfs /sys/kernel/debug/
>  # cd /sys/kernel/debug/tracing
>  # echo function > current_tracer
>  # echo 1 > options/func_pstore
>  # reboot -f
>  [...]
>  # mount -t pstore pstore /mnt/
>  # tail /mnt/ftrace-ramoops
>  0 ffffffff8101ea64  ffffffff8101bcda  native_apic_mem_read <- disconnect_bsp_APIC+0x6a/0xc0
>  0 ffffffff8101ea44  ffffffff8101bcf6  native_apic_mem_write <- disconnect_bsp_APIC+0x86/0xc0
>  0 ffffffff81020084  ffffffff8101a4b5  hpet_disable <- native_machine_shutdown+0x75/0x90
>  0 ffffffff81005f94  ffffffff8101a4bb  iommu_shutdown_noop <- native_machine_shutdown+0x7b/0x90
>  0 ffffffff8101a6a1  ffffffff8101a437  native_machine_emergency_restart <- native_machine_restart+0x37/0x40
>  0 ffffffff811f9876  ffffffff8101a73a  acpi_reboot <- native_machine_emergency_restart+0xaa/0x1e0
>  0 ffffffff8101a514  ffffffff8101a772  mach_reboot_fixups <- native_machine_emergency_restart+0xe2/0x1e0
>  0 ffffffff811d9c54  ffffffff8101a7a0  __const_udelay <- native_machine_emergency_restart+0x110/0x1e0
>  0 ffffffff811d9c34  ffffffff811d9c80  __delay <- __const_udelay+0x30/0x40
>  0 ffffffff811d9d14  ffffffff811d9c3f  delay_tsc <- __delay+0xf/0x20
> 
> Mostly the code comes from trace_persistent.c driver found in the
> Android git tree, written by Colin Cross <ccross@...roid.com>
> (according to sign-off history). I reworked the driver a little bit,
> and ported it to pstore subsystem.


This looks fine to me, but as it touches pstore and tracing code, I
can't apply it without acks from the relevant maintainers/owners.

thanks,

greg k-h
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