On Wed, Jan 6, 2016 at 9:28 AM, John Stultz <john.stu...@linaro.org> wrote:
> On Wed, Jan 6, 2016 at 5:00 AM, Prarit Bhargava <pra...@redhat.com> wrote:
>> -ktime_t ktime_get_with_offset(enum tk_offsets offs)
>> +ktime_t ktime_get_with_offset(enum tk_offsets offs, int trylock)
>> {
>> struct timekeeper *tk = &tk_core.timekeeper;
>> unsigned int seq;
>> ktime_t base, *offset = offsets[offs];
>> s64 nsecs;
>> + unsigned long flags = 0;
>> +
>> + if (unlikely(!timekeeping_initialized))
>> + return ktime_set(0, 0);
>>
>> WARN_ON(timekeeping_suspended);
>>
>> + if (trylock && !raw_spin_trylock_irqsave(&timekeeper_lock, flags))
>> + return ktime_set(KTIME_MAX, 0);
>
> Wait.. this doesn't make sense. The timekeeper lock is only for reading.
Only for writing.. sorry.. still drinking my coffee.
> What I was suggesting to you off line is to have something that avoids
> spinning on the seqcounter should if a bug occurs and we IPI all the
> cpus, that we don't deadlock or block any printk messages.
And more clearly here, if a cpu takes a write on the seqcounter in
update_wall_time() and at that point another cpu hits a bug, and IPIs
the cpus, the system would deadlock. That's really what I want to
avoid.
thanks
-john
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
