Re: is printk() safe within a timekeeper_seq write section?

[John Stultz]

On 03/12/2014 02:21 AM, Jiri Bohac wrote:
> On Tue, Mar 11, 2014 at 02:54:13PM -0700, John Stultz wrote:
>> Ok, so a generic solution is probably not going to be worth it then. My
>> thought was that since we do a very limited amount of informational
>> printks in the timekeeping code, we can be fairly safe delaying the
>> print-out until we drop the locks.
>>
>> For timekeeping, its really 4 call sites:
>> * invalid inject_sleep_time deltas
>> * > 11% clocksource freq adjustments
>> * insert leap second
>> * delete leap second
> I believe these last two were made safe by 
> commit ca4523cd (timekeeping: Shorten seq_count region). 
>
> write_seqcount_begin(&timekeeper_seq) is now done after the
> accumulate_nsecs_to_secs(tk) from where the printks are called.

So I started looking into deferring the printk with a small local
buffer, but I suddenly realized there are all these WARN_ON's around
which would likely have the same problem, no?

So I'm starting to doubt we can safely get away with a timekeeping
specific hack to defer the printk. :(

thanks
-john




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