|From:||Avery Pennarun <firstname.lastname@example.org>|
|To:||Andrew Morton <email@example.com>, Josh Triplett <firstname.lastname@example.org>, "Paul E. McKenney" <email@example.com>, Ingo Molnar <firstname.lastname@example.org>, "David S. Miller" <email@example.com>, Peter Zijlstra <firstname.lastname@example.org>, "Fabio M. Di Nitto" <email@example.com>, Avery Pennarun <firstname.lastname@example.org>, Johannes Weiner <email@example.com>, Olaf Hering <firstname.lastname@example.org>, Paul Gortmaker <email@example.com>, Tejun Heo <firstname.lastname@example.org>, "H. Peter Anvin" <email@example.com>, Yinghai LU <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org|
|Subject:||[PATCH 0/5] Persist printk buffer across reboots.|
|Date:||Tue, 13 Mar 2012 01:36:36 -0400|
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. Patch generated against v3.3-rc7. Avery Pennarun (5): mm: bootmem: BUG() if you try to allocate bootmem too late. mm: bootmem: it's okay to reserve_bootmem an invalid address. mm: nobootmem: implement reserve_bootmem() in terms of memblock. printk: use alloc_bootmem() instead of memblock_alloc(). printk: CONFIG_PRINTK_PERSIST: persist printk buffer across reboots. init/Kconfig | 12 ++++++ kernel/printk.c | 117 +++++++++++++++++++++++++++++++++++++++++++++--------- mm/bootmem.c | 10 ++++- mm/nobootmem.c | 23 +++++++++++ 4 files changed, 140 insertions(+), 22 deletions(-) -- 184.108.40.206 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to email@example.com More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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