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SubjectRe: [RFC PATCH 02/12] On Tue, 23 Sep 2008, David Miller wrote:
On Sat, Oct 4, 2008 at 4:02 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Sat, 4 Oct 2008, Jiri Kosina wrote:
>> On Fri, 3 Oct 2008, Jesse Brandeburg wrote:
>> > Our experience is different. We are also testing with the "protection
>> > patch" reverted.
>> > We see that the problem specifically comes and goes when
>> > removing/adding the use of set_memory_ro/set_memory_rw to the driver.
>>
>> But if this patch (which is an obvious workaround, compared to the other
>> patches which fix real bugs, right?) would be catching some malicious
>> accessess to the mapped EEPROM, there should be stacktraces present in the
>> kernel log, right?

yes, but I think it is just changing timing, i don't see any backtraces either.

> Exactly. The access to a ro region results in a fault. I have nowhere
> seen that trigger, but I can reproduce the trylock() WARN_ON, which
> confirms that there is concurrent access to the NVRAM registers. The
> backtrace pattern is similar to the one you have seen.

are you still getting WARN_ON *with* all the mutex based fixes already applied?

with the mutex patches in place (without protection patch) we are
still reproducing the issue, until we apply the set_memory_ro patch.
I had no luck on friday setting a hardware breakpoint on memory access
with kgdb to catch the writer with a breakpoint.


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