Timur Tabi wrote:
On Wed, Mar 11, 2009 at 12:09 AM, Roland Dreier <rdre...@cisco.com> wrote:
Are there really cases where spinning for 1 jiffy is too long of a
timeout?
If the result is a timeout, then I say no. A timeout is an error
condition, and the code will usually terminate.
[snip]
Two jiffies can be a very long time.
One jiffy is fine, but two is just too long?
Given that it only happens in cases of malfunctioning hardware (or a
buggy driver), it seems reasonable as long as preemption isn't disabled
(I'm assuming anyone that cares about a rare latency of a couple jiffies
is using a preemptible kernel).
Besides, if this function is
used when interrupts are disabled, I believe that on some platforms,
jiffies never increments. If so, we can't use the actual 'jiffies'
variable.
Disallow that, enforced with a call to might_sleep().
Alternatively, do something with get_cycles(), and have some sort of
#define by which arches can say if get_cycles actually works. In the
absence of a working get_cycles() or equivalent, timeouts with
interrupts disabled aren't going to happen whether we abstract it with a
macro or not.
-Scott
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@ozlabs.org
https://ozlabs.org/mailman/listinfo/linuxppc-dev
