Re: [PATCH] alarmtimer: don't rate limit one-shot timers

[Greg Hackmann]

On 07/24/2017 11:21 AM, Greg KH wrote:
> On Mon, Jul 24, 2017 at 10:19:24AM -0700, Greg Hackmann wrote:
> > Commit ff86bf0c65f1 ("alarmtimer: Rate limit periodic intervals") sets a
> > minimum bound on the alarm timer interval.  This minimum bound shouldn't
> > be applied if the interval is 0.  Otherwise, one-shot timers will be
> > converted into periodic ones.
> >
> > This patch is against 4.9.39, and is only needed in -stable trees.
> > 4.13-rc2 isn't impacted due to a later refactoring.
>
> What refactoring patch fixed this up?

f2c45807d399 ("alarmtimer: Switch over to generic set/get/rearm routine")

> As this was a 4.12 patch, 4.12-stable needs this fix as well, right?

Looks like it, but I haven't actually tried 4.12 yet to confirm.

> Also, was there some test-case that you caught this with that perhaps
> could be added to LTP or kselftests?

Unfortunately not a direct testcase.  This first showed up as a 
regression in AOSP's userspace Bluetooth stack, which uses 
CLOCK_BOOTTIME_ALARM internally.

I'm working on a patch to add one-shot timer testcases to 
set-timer-lat.c, which would have caught this.  (I wrote a very rough 
test program to make sure this patch fixes the regression, but 
set-timer-lat.c already exists and is more comprehensive.)