From: John Stultz <john.stultz@linaro.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Colin Cross <ccross@android.com>,
Android Kernel Team <kernel-team@android.com>,
tony.luck@intel.com
Subject: Re: [PATCH 11/13] android: persistent_trace: ftrace into persistent_ram
Date: Wed, 07 Mar 2012 14:40:54 -0800 [thread overview]
Message-ID: <1331160054.2191.202.camel@work-vm> (raw)
In-Reply-To: <20120307221002.GC16652@kroah.com>
On Wed, 2012-03-07 at 14:10 -0800, Greg KH wrote:
> On Wed, Mar 07, 2012 at 01:58:21PM -0800, John Stultz wrote:
> > From: Colin Cross <ccross@android.com>
> >
> > persistent_trace uses the ftrace infrastructure, but traces
> > into a persistent_ram buffer instead of the regular ftrace
> > ringbuffer. After a reset or panic, the trace can be
> > decoded with cat /sys/kernel/debug/persistent_trace.
>
> Has this patch been run by the tracing kernel developers?
Probably not. If you'd prefer, we can drop this one and come back to it
later.
> And what's the status on merging the persistent_ram stuff in with the
> in-kernel api for this type of thing? That should then get rid of this
> separate tracing module, or at the least, let it be accepted directly by
> the tracing developers and not need to go through staging, right?
>From my understanding, ram_console/persistent_ram functionality isn't
really the same as pstore/ramoops.
When asked earlier about this, Colin said:
"pstore is just an interface to write to a persistent storage, with a
tiny driver on it to dump console messages after a panic. With the
number of crashes we see on ARM cpus that are not panics (mostly
watchdog resets), logging only after a panic is not appropriate, so it
can't replace ramconsole. persistent_ram could easily be a pstore
driver, but that would not give any new useful functionality, since
ramconsole is better for us than pstore_dump.
Looking at ramoops, it is exactly the same as pstore on ioremapped
ram, but was originally implemented separately. I see patches now
that convert it to a pstore backend, which leaves us in the same state
as above - only logging panics."
As for the long term merging story, I think Colin's idea of using
persistent_ram a backing for pstore, then adapting pstore as needed to
provide similar continuous console logging like ram_console might be a
way forward, but I don't know of anyone actively working on that atm.
Tony: Do you have any thoughts here?
thanks
-john
next prev parent reply other threads:[~2012-03-07 22:41 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-07 21:58 [PATCH 00/13] staging: Android updates John Stultz
2012-03-07 21:58 ` [PATCH 01/13] android: lowmemorykiller: Fix warning on 64bit John Stultz
2012-03-07 22:04 ` Greg KH
2012-03-07 22:24 ` John Stultz
2012-03-07 21:58 ` [PATCH 02/13] android: ram_console: set CON_ANYTIME console flag John Stultz
2012-03-07 22:07 ` Greg KH
2012-03-07 21:58 ` [PATCH 03/13] android: ram_console: move footer strings John Stultz
2012-03-07 21:58 ` [PATCH 04/13] android: ram_console: drop early buffer support John Stultz
2012-03-07 21:58 ` [PATCH 05/13] android: ram_console: drop verbose ram_console support John Stultz
2012-03-07 21:58 ` [PATCH 06/13] android: ram_console: split out persistent ram John Stultz
2012-03-07 21:58 ` [PATCH 07/13] android: persistent_ram: refactor ecc support John Stultz
2012-03-07 22:21 ` Daniel Walker
2012-03-07 21:58 ` [PATCH 08/13] android: persistent_ram: handle reserving and mapping memory John Stultz
2012-03-07 22:08 ` Greg KH
2012-03-07 22:16 ` John Stultz
2012-03-08 1:46 ` Greg KH
2012-03-07 21:58 ` [PATCH 09/13] android: persistent_ram: make persistent_ram_write atomic John Stultz
2012-03-07 21:58 ` [PATCH 10/13] android: persistent_ram: add notrace to persistent_ram_write John Stultz
2012-03-07 21:58 ` [PATCH 11/13] android: persistent_trace: ftrace into persistent_ram John Stultz
2012-03-07 22:10 ` Greg KH
2012-03-07 22:40 ` John Stultz [this message]
2012-03-07 21:58 ` [PATCH 12/13] android: staging: ram_console: fix crash in ram_console_late_init John Stultz
2012-03-07 21:58 ` [PATCH 13/13] android: ram_console: honor dmesg_restrict John Stultz
2012-03-07 22:10 ` Greg KH
2012-03-07 22:11 ` [PATCH 00/13] staging: Android updates Greg KH
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