Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architectureindependent macro
From: Stephen Boyd
Date: Wed Jul 31 2013 - 20:04:23 EST
On 07/31/13 16:44, Timur Tabi wrote:
> On Wed, Jul 31, 2013 at 2:16 AM, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote:
>> What do you do here if jiffies aren't incrementing (i.e
>> interrupts are disabled). The time_before() check won't work
>> there and it would be nice if we were able to use this in such
>> situations. I think powerpc gets around this by reading the
>> hardware timer directly?
> I believe that jiffies is always a global variable. It should behave
> the same on PowerPC as on other architectures.
Yes it's global but it doesn't increment while interrupts are off.
> The answer to your question is that you should not use
> spin_event_timeout() in interrupt context, because it yields.
If it yields why are we using udelay? Why not usleep_range()? It would
be useful to have a variant that worked in interrupt context and it
looked like that was almost possible.
BTW, couldn't we skip the first patch and just use usecs_to_jiffies()?
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
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/