Re: 4.0.2-stable-queue build failures due to 'clockevents: Fix cpu_down() race for hrtimer based broadcasting'

[Preeti U Murthy <preeti@linux.vnet.ibm.com>]

On 05/12/2015 05:44 PM, Greg Kroah-Hartman wrote:
> On Tue, May 12, 2015 at 11:37:09AM +0530, Preeti U Murthy wrote:
>> On 05/11/2015 06:32 PM, Guenter Roeck wrote:
>>> On Mon, May 11, 2015 at 11:20:17AM +0530, Preeti U Murthy wrote:
>>>> On 05/11/2015 06:29 AM, Guenter Roeck wrote:
>>>>> Build is still going on, so there may be other affected architectures.
>>>>>
>>>>> ---
>>>>>
>>>>> Building ia64:defconfig ... failed
>>>>> Building parisc:generic-32bit_defconfig ... failed
>>>>> --------------
>>>>> Error log:
>>>>> kernel/cpu.c: In function '_cpu_down':
>>>>> kernel/cpu.c:415:2: error: implicit declaration of function
>>>>> 'hotplug_cpu__broadcast_tick_pull' [-Werror=implicit-function-declaration]
>>>>> cc1: some warnings being treated as errors
>>>>>
>>> [ ... ]
>>>
>>>>> git bisect good c20b6545f649724a733e008e7124fa9d1e114c71
>>>>> # first bad commit: [c71309a3658d323d56261d4590b2c5214e61b05f]
>>>>> clockevents: Fix cpu_down() race for hrtimer based broadcasting
>>>>>
>>>>> ---
>>>>>
>>>>> Reverting the bad commit fixes the problem.
>>>>
>>>> Please let me know if the following patch fixes the issue:
>>>>
>>>>     clockevents: Fix build error caused by fix for hotplug race with hrtimer broadcast
>>>>     
>>>>     commit: c71309a3658d ("clockevents: Fix cpu_down() race for hrtimer based broadcasting")
>>>>     causes a build error on certain archs where CONFIG_GENERIC_CLOCKEVENTS
>>>>     is not set. This patch fixes this.
>>>>     
>>>> +++ b/include/linux/tick.h
>>>> @@ -134,6 +134,7 @@ static inline void tick_clock_notify(void) { }
>>>>  static inline int tick_check_oneshot_change(int allow_nohz) { return 0; }
>>>>  static inline void tick_irq_enter(void) { }
>>>>  static inline int tick_oneshot_mode_active(void) { return 0; }
>>>> +static inline void hotplug_cpu__broadcast_tick_pull(int dead_cpu) { }
>>>
>>> Possibly it does, but why is the back-port so much different from the original
>>> patch ? This would be the third declaration of this dummy function, which just
>>> seems wrong. The original patch only needs one.
>>
>> That is because these two patches simplified the layout of the related
>> files.
>>
>> c1797baf6880174: tick: Move core only declarations and functions to core
>> b7475eb599ddb2e: tick: Simplify tick-internal.h
>>
>> These patches are not yet in stable.
> 
> Then you should have asked for them to be merged as well.  I don't want
> to deviate from what is in Linus's tree if at all possible.  This long
> email exchange is the exact reason why (patch errors, build errors,
> wasted time, confusion, etc.)
> 
> Please resend me the exact git commit ids that you wish to have added to
> the stable tree, in the order you wish to have them added.  If something
> needs to be changed/backported, be very explicit as to why it needs to
> be changed, and that you have done so.

Ok Greg, I will do so. I apologize for the confusion created.

Regards
Preeti U Murthy
> 
> thanks,
> 
> greg k-h
>