Messages in this thread | | | Date | Fri, 18 Nov 2016 14:42:15 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 15/20] ARM/hw_breakpoint: Convert to hotplug state machine |
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On Fri, 18 Nov 2016, Will Deacon wrote: > On Fri, Nov 18, 2016 at 02:11:58PM +0100, Thomas Gleixner wrote: > > But it's guaranteed that cpuhp_setup_state() will not return before the > > callback has been invoked on each online cpu. > > Ok, that's good. > > > If cpus are not yet online when that code is invoked, then it's the same > > behaviour as before. It will be invoked when the cpu comes online. > > Just to check, but what stops a CPU from coming online between the call > to cpuhp_setup_state and the call to cpuhp_remove_state_nocalls in the > case of failure (debug_err_mask isn't empty)?
Indeed! I missed that part. So we still need a get/put_online_cpus() protection around all of this.
Just for curiosity sake. Wouldn't it be simpler and less error prone to make the ARM_DBG_READ/WRITE macros use the exception table and handle that in the undefined instruction handler to avoid this hook dance?
Thanks,
tglx
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