From: Stephen Boyd <sboyd@codeaurora.org>
To: Avery Pennarun <apenwarr@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Josh Triplett <josh@joshtriplett.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@elte.hu>,
"David S. Miller" <davem@davemloft.net>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
"Fabio M. Di Nitto" <fdinitto@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Olaf Hering <olaf@aepfle.de>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Tejun Heo <tj@kernel.org>, "H. Peter Anvin" <hpa@linux.intel.com>,
Yinghai LU <yinghai@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 0/5] Persist printk buffer across reboots.
Date: Tue, 13 Mar 2012 01:32:32 -0700 [thread overview]
Message-ID: <4F5F0620.2020404@codeaurora.org> (raw)
In-Reply-To: <1331617001-20906-1-git-send-email-apenwarr@gmail.com>
On 3/12/2012 10:36 PM, Avery Pennarun wrote:
> The last patch in this series implements a new CONFIG_PRINTK_PERSIST option
> that, when enabled, puts the printk buffer in a well-defined memory location
> so that we can keep appending to it after a reboot. The upshot is that,
> even after a kernel panic or non-panic hard lockup, on the next boot
> userspace will be able to grab the kernel messages leading up to it. It
> could then upload the messages to a server (for example) to keep crash
> statistics.
>
> The preceding patches in the series are mostly just things I fixed up while
> working on that patch.
>
> Some notes:
>
> - I'm not totally sure of the locking or portability issues when calling
> memblock or bootmem. This all happens really early, and I *think*
> interrupts are still disabled at that time, so it's probably okay.
>
> - Tested this version on x86 (kvm) and it works with soft reboot (ie. reboot
> -f). Since some BIOSes wipe the memory during boot, you might not have
> any luck. It should be great on many embedded systems, though, including
> the MIPS system I've tested a variant of this patch on. (Our MIPS build
> is based on a slightly older kernel so it's not 100% the same, but I think
> this should behave identically.)
>
> - The way we choose a well-defined memory location is slightly suspicious
> (we just count down from the top of the address space) but I've tested it
> pretty carefully, and it seems to be okay.
>
> - In printk.c with CONFIG_PRINTK_PERSIST set, we're #defining words like
> log_end. It might be cleaner to replace all instances of log_end with
> LOG_END to make this more clear. This is also the reason the struct
> logbits members start with _: because otherwise they conflict with the
> macro. Suggestions welcome.
Android has something similar called ram_console (see
staging/android/ram_console.c). The console is dumped to a ram buffer
that is reserved very early in platform setup code. Then when the phone
reboots you can cat /proc/last_kmsg to get the previous kernel message
for debugging. Can you use that code?
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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WARNING: multiple messages have this Message-ID (diff)
From: Stephen Boyd <sboyd@codeaurora.org>
To: Avery Pennarun <apenwarr@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Josh Triplett <josh@joshtriplett.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@elte.hu>,
"David S. Miller" <davem@davemloft.net>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
"Fabio M. Di Nitto" <fdinitto@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Olaf Hering <olaf@aepfle.de>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Tejun Heo <tj@kernel.org>, "H. Peter Anvin" <hpa@linux.intel.com>,
Yinghai LU <yinghai@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 0/5] Persist printk buffer across reboots.
Date: Tue, 13 Mar 2012 01:32:32 -0700 [thread overview]
Message-ID: <4F5F0620.2020404@codeaurora.org> (raw)
In-Reply-To: <1331617001-20906-1-git-send-email-apenwarr@gmail.com>
On 3/12/2012 10:36 PM, Avery Pennarun wrote:
> The last patch in this series implements a new CONFIG_PRINTK_PERSIST option
> that, when enabled, puts the printk buffer in a well-defined memory location
> so that we can keep appending to it after a reboot. The upshot is that,
> even after a kernel panic or non-panic hard lockup, on the next boot
> userspace will be able to grab the kernel messages leading up to it. It
> could then upload the messages to a server (for example) to keep crash
> statistics.
>
> The preceding patches in the series are mostly just things I fixed up while
> working on that patch.
>
> Some notes:
>
> - I'm not totally sure of the locking or portability issues when calling
> memblock or bootmem. This all happens really early, and I *think*
> interrupts are still disabled at that time, so it's probably okay.
>
> - Tested this version on x86 (kvm) and it works with soft reboot (ie. reboot
> -f). Since some BIOSes wipe the memory during boot, you might not have
> any luck. It should be great on many embedded systems, though, including
> the MIPS system I've tested a variant of this patch on. (Our MIPS build
> is based on a slightly older kernel so it's not 100% the same, but I think
> this should behave identically.)
>
> - The way we choose a well-defined memory location is slightly suspicious
> (we just count down from the top of the address space) but I've tested it
> pretty carefully, and it seems to be okay.
>
> - In printk.c with CONFIG_PRINTK_PERSIST set, we're #defining words like
> log_end. It might be cleaner to replace all instances of log_end with
> LOG_END to make this more clear. This is also the reason the struct
> logbits members start with _: because otherwise they conflict with the
> macro. Suggestions welcome.
Android has something similar called ram_console (see
staging/android/ram_console.c). The console is dumped to a ram buffer
that is reserved very early in platform setup code. Then when the phone
reboots you can cat /proc/last_kmsg to get the previous kernel message
for debugging. Can you use that code?
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
next prev parent reply other threads:[~2012-03-13 8:32 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-13 5:36 [PATCH 0/5] Persist printk buffer across reboots Avery Pennarun
2012-03-13 5:36 ` Avery Pennarun
2012-03-13 5:36 ` [PATCH 1/5] mm: bootmem: BUG() if you try to allocate bootmem too late Avery Pennarun
2012-03-13 5:36 ` Avery Pennarun
2012-03-13 5:36 ` [PATCH 2/5] mm: bootmem: it's okay to reserve_bootmem an invalid address Avery Pennarun
2012-03-13 5:36 ` Avery Pennarun
2012-03-13 5:36 ` [PATCH 3/5] mm: nobootmem: implement reserve_bootmem() in terms of memblock Avery Pennarun
2012-03-13 5:36 ` Avery Pennarun
2012-03-13 5:36 ` [PATCH 4/5] printk: use alloc_bootmem() instead of memblock_alloc() Avery Pennarun
2012-03-13 5:36 ` Avery Pennarun
2012-03-13 6:13 ` Yinghai Lu
2012-03-13 6:13 ` Yinghai Lu
2012-03-13 6:40 ` Avery Pennarun
2012-03-13 6:40 ` Avery Pennarun
2012-03-13 8:26 ` Ingo Molnar
2012-03-13 8:26 ` Ingo Molnar
2012-03-13 21:50 ` Yinghai Lu
2012-03-13 21:50 ` Yinghai Lu
2012-03-14 2:23 ` Avery Pennarun
2012-03-14 2:23 ` Avery Pennarun
2012-03-13 5:36 ` [PATCH 5/5] printk: CONFIG_PRINTK_PERSIST: persist printk buffer across reboots Avery Pennarun
2012-03-13 5:36 ` Avery Pennarun
2012-03-13 5:53 ` [PATCH 0/5] Persist " David Miller
2012-03-13 5:53 ` David Miller
2012-03-13 6:00 ` Avery Pennarun
2012-03-13 6:00 ` Avery Pennarun
2012-03-13 6:50 ` David Miller
2012-03-13 6:50 ` David Miller
2012-03-13 7:14 ` Avery Pennarun
2012-03-13 7:14 ` Avery Pennarun
2012-03-13 7:18 ` David Miller
2012-03-13 7:18 ` David Miller
2012-03-13 8:10 ` Avery Pennarun
2012-03-13 8:10 ` Avery Pennarun
2012-03-13 8:16 ` David Miller
2012-03-13 8:16 ` David Miller
2012-03-13 13:50 ` Peter Zijlstra
2012-03-13 13:50 ` Peter Zijlstra
2012-03-14 1:57 ` Daniel Walker
2012-03-14 1:57 ` Daniel Walker
2012-03-13 8:32 ` Stephen Boyd [this message]
2012-03-13 8:32 ` Stephen Boyd
2012-03-13 17:08 ` Daniel Walker
2012-03-13 17:08 ` Daniel Walker
2012-03-13 22:10 ` Andrew Morton
2012-03-13 22:10 ` Andrew Morton
2012-03-14 2:19 ` Daniel Walker
2012-03-14 2:19 ` Daniel Walker
2012-03-15 22:10 ` Seiji Aguchi
2012-03-15 22:10 ` Seiji Aguchi
2012-03-14 2:21 ` Avery Pennarun
2012-03-14 2:21 ` Avery Pennarun
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