On Wed, Jan 06, 2016 at 08:00:33AM -0500, Prarit Bhargava 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);
> +
Are you trying to avoid a deadlock caused by calling printk() with
timekeeper_lock locked?
I believe this is already unsafe, as explained in the commit log
of 6d9bcb62 (timekeeping: use printk_deferred when holding
timekeeping seqlock).
So directly calling ktime_get() from printk would just turn a
rare deadlock into a certain one - perhaps a good thing?
--
Jiri Bohac <[email protected]>
SUSE Labs, SUSE CZ
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