Re: [PATCH v3 1/7] arm64: introduce basic aarch64 instructiondecoding helpers

[Will Deacon]

On Wed, Oct 16, 2013 at 06:14:50PM +0100, Jiang Liu wrote:
> On 10/16/2013 11:36 PM, Jiang Liu wrote:
> > On 10/16/2013 06:51 PM, Will Deacon wrote:
> >> Take care here:
> >>
> >> 	- This doesn't guarantee that CPUs exclusively see new_insn (they
> >> 	  may see old_insn, even after patching)
> > Good point. Still need some synchronization mechanism lighter than
> > stop_machine(). How about kick_all_cpus_sync(), which should be lighter
> > than stop_machine()?
> For jump label, x86 uses three smp_call_function() to replace a
> stop_machine(). Seems it's valuable for us to use just one
> kick_all_cpus_sync() to avoid a stop_machine().

Yes, the exception return after handling the IPI from kick_all_cpus_sync
should be enough to synchronise the pipeline, providing that all cache
maintenance by the CPU writing the new instructions has completed (if you're
using flush_icache_range then you're fine).

Will
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/