Re: [RFC] Fast assurate clock readable from user space and NMIhandler

From: john stultz
Date: Tue Feb 27 2007 - 14:41:24 EST


On Tue, 2007-02-27 at 14:04 -0500, Mathieu Desnoyers wrote:
> __get_nsec_offset : reads clock->cycle_last. Should be called with
> xtime_lock held. (ok so far, but see below)
>
> change_clocksource
> clock->cycle_last = now; (non atomic 64 bits update. Not protected by
> any lock ?) -> this would race with __get_nsec_offset ?

Minor nit (it could probably use a comment fixup): its only called from
update_wall_time, which holds xtime_lock.

> update_wall_time
> Called from timer interrupt. Holds xtime_lock and has a priority higher
> than other interrupts. Other clock->cycle_last protected by
> write_seqlock_irqsave.

-john

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/