[PATCH 14/14] pstore/platform: Remove automatic updates
keescook at chromium.org
Mon May 21 19:59:59 UTC 2012
On Fri, May 18, 2012 at 3:26 PM, Anton Vorontsov
<anton.vorontsov at linaro.org> wrote:
> Having automatic updates seems pointless, and even dangerous
> and thus counter-productive:
> 1. If we can mount pstore, or read files, we can as well read
> /proc/kmsg. So, there's little point in duplicating the
> functionality and present the same information but via another
> userland ABI;
> 2. Expecting the kernel to behave sanely after oops/panic is naive.
> It might work, but you'd rather not try it. Screwed up kernel
> can do rather bad things, like recursive faults; and pstore
> rather provoking bad things to happen. It uses:
> 1. Timers (assumes sane interrupts state);
> 2. Workqueues and mutexes (assumes scheduler in a sane state);
> 3. kzalloc (a working slab allocator);
> That's too much for a dead kernel, so the debugging facility
> itself might just make debugging harder, which is not what
> we want.
> So, let's remove the automatic updates, this keeps things simple
> and safe.
> (Maybe for non-oops message types it would make sense to add
> automatic updates, but so far I don't see any use case for this.
> Even for tracing, it has its own run-time/normal ABI, so we're
> only interested in pstore upon next boot, to retrieve what has
> gone wrong with HW or SW.)
Hrm. This complicates testing a bit. I need more convincing. :)
Systems run with panic_on_oops=0, and plenty of failure paths will
just kill "current" instead of bringing the entire system down. I
would much rather allow for the possibility to get oopses when they
happen than to have to wait a full reboot cycle to "notice" them.
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