Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Ingo Molnar
* Peter Zijlstra pet...@infradead.org wrote: On Thu, Apr 02, 2015 at 12:42:27PM +0200, Ingo Molnar wrote: So why not use a suitable CPU_DOWN* notifier for this, instead of open coding it all into a random place in the hotplug machinery? Because notifiers are crap? ;-) [...] No doubt -

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Peter Zijlstra
On Thu, Apr 02, 2015 at 02:12:47PM +0200, Ingo Molnar wrote: Okay. I'll resurrect the fix with a hotplug_cpu__tick_pull() name - agreed? Sure. Also, I improved the changelog (attached below), but decided against applying it until these questions are cleared - please use that for

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Preeti U Murthy
On 04/02/2015 04:12 PM, Ingo Molnar wrote: * Preeti U Murthy pre...@linux.vnet.ibm.com wrote: It was found when doing a hotplug stress test on POWER, that the machine either hit softlockups or rcu_sched stall warnings. The issue was traced to commit 7cba160ad789a powernv/cpuidle: Redesign

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Ingo Molnar
* Preeti U Murthy pre...@linux.vnet.ibm.com wrote: On 04/02/2015 04:12 PM, Ingo Molnar wrote: * Preeti U Murthy pre...@linux.vnet.ibm.com wrote: It was found when doing a hotplug stress test on POWER, that the machine either hit softlockups or rcu_sched stall warnings. The issue

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Peter Zijlstra
On Thu, Apr 02, 2015 at 12:42:27PM +0200, Ingo Molnar wrote: So why not use a suitable CPU_DOWN* notifier for this, instead of open coding it all into a random place in the hotplug machinery? Because notifiers are crap? ;-) Its entirely impossible to figure out what's happening to core code in

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Preeti U Murthy
On 04/02/2015 05:01 PM, Ingo Molnar wrote: * Preeti U Murthy pre...@linux.vnet.ibm.com wrote: On 04/02/2015 04:12 PM, Ingo Molnar wrote: * Preeti U Murthy pre...@linux.vnet.ibm.com wrote: It was found when doing a hotplug stress test on POWER, that the machine either hit softlockups or

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Preeti U Murthy
On 04/02/2015 05:42 PM, Ingo Molnar wrote: * Peter Zijlstra pet...@infradead.org wrote: On Thu, Apr 02, 2015 at 12:42:27PM +0200, Ingo Molnar wrote: So why not use a suitable CPU_DOWN* notifier for this, instead of open coding it all into a random place in the hotplug machinery? Because

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-04-02 Thread Ingo Molnar
* Preeti U Murthy pre...@linux.vnet.ibm.com wrote: It was found when doing a hotplug stress test on POWER, that the machine either hit softlockups or rcu_sched stall warnings. The issue was traced to commit 7cba160ad789a powernv/cpuidle: Redesign idle states management, which exposed the

[PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-03-30 Thread Preeti U Murthy
It was found when doing a hotplug stress test on POWER, that the machine either hit softlockups or rcu_sched stall warnings. The issue was traced to commit 7cba160ad789a powernv/cpuidle: Redesign idle states management, which exposed the cpu down race with hrtimer based broadcast mode(Commit

Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

2015-03-30 Thread Nicolas Pitre
On Mon, 30 Mar 2015, Preeti U Murthy wrote: It was found when doing a hotplug stress test on POWER, that the machine either hit softlockups or rcu_sched stall warnings. The issue was traced to commit 7cba160ad789a powernv/cpuidle: Redesign idle states management, which exposed the cpu down