lkml.org 
[lkml]   [2013]   [Oct]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] sched_clock: fix postinit no sched_clock function check
On 10/02/13 10:14, Santosh Shilimkar wrote:
> On Wednesday 02 October 2013 01:09 PM, Will Deacon wrote:
>> On Wed, Oct 02, 2013 at 05:55:28PM +0100, Santosh Shilimkar wrote:
>>> The sched_clock code uses 2 levels of function pointers, sched_clock_func()
>>> and read_sched_clock() but the no sched_clock check in postinit() just
>>> checks read_sched_clock().
>>>
>>> This leads to kernel falling back to jiffy based sched clock even in
>>> presence of sched_clock_func() which is not desirable.
>>>
>>> Fix the postinit() check to avoid the issue. Probably the issue is hidden
>>> so far on most of the arm SOCs because of already existing sched_clock
>>> registrations apart from arch_timer sched_clock. One can reproduce the
>>> issue by just have arch_timer as sched_clock
>> Isn't this just an issue with the arch timer driver not calling
>> setup_sched_clock? Instead, we munge around with sched_clock_func directly,
>> which doesn't appear to be the way anybody else deals with this.
>>
> I thought about that option as well but was not sure since even in that case
> the check is not complete. We just ensure that function is popullated.

Yes, nothing is actually broken because sched_clock_func() won't try to
use the jiffy based read_sched_clock() function. I'm not sure we
actually need this patch besides to remove a useless timer that updates
the jiffy epoch. Can we wait until my 64-bit sched_clock patch series
lands in 3.13? It looks like I still need an ack from Will or Catalin on
the architected timer patch before the clocksource folks pick it up.

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation



\
 
 \ /
  Last update: 2013-10-02 19:41    [W:0.047 / U:0.288 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site