----- On Jul 2, 2015, at 3:23 PM, Paul E. McKenney paul...@linux.vnet.ibm.com
wrote:
> On Thu, Jul 02, 2015 at 06:47:47PM +0000, Mathieu Desnoyers wrote:
>> ----- On Jul 2, 2015, at 2:35 PM, Ingo Molnar mi...@kernel.org wrote:
>>
>> > * Paul E. McKenney <paul...@linux.vnet.ibm.com> wrote:
>> >
>> >> > And it's not like it's that hard to stem the flow of algorithmic
>> >> > sloppiness at
>> >> > the source, right?
>> >>
>> >> OK, first let me make sure that I understand what you are asking for:
>> >>
>> >> 1. Completely eliminate synchronize_rcu_expedited() and
>> >> synchronize_sched_expedited(), replacing all uses with their
>> >> unexpedited counterparts. (Note that synchronize_srcu_expedited()
>> >> does not wake up CPUs, courtesy of its read-side memory barriers.)
>> >> The fast-boot guys are probably going to complain, along with
>> >> the networking guys.
>> >>
>> >> 2. Keep synchronize_rcu_expedited() and
>> >> synchronize_sched_expedited(),
>> >> but push back hard on any new uses and question any existing uses.
>> >>
>> >> 3. Revert 74b51ee152b6 ("ACPI / osl: speedup grace period in
>> >> acpi_os_map_cleanup").
>> >>
>> >> 4. Something else?
>> >
>> > I'd love to have 1) but 2) would be a realistic second best option? ;-)
>>
>> Perhaps triggering a printk warning if use of
>> synchronize_{rcu,sched}_expedited() go beyond of certain rate might be
>> another option ? If we detect that a caller calls it too often, we could
>> emit a printk warning with a stack trace. This should ensure everyone
>> is very careful about where they use it.
>
> My first thought is that a storm of expedited grace periods would be
> most likely to show up in some error condition, and having them
> splat might obscure the splats identifying the real problem. Or did
> you have something else in mind here?
Fair point! So I guess your checkpatch approach is more appropriate.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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