[lkml]   [2007]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
>>>> And no, RMW on MMIO isn't "problematic" at all, either.
>>>> An RMW op is a read op, a modify op, and a write op, all rolled
>>>> into one opcode. But three actual operations.
>>> Maybe for some CPUs, but not all. ARM for instance can't use the
>>> load exclusive and store exclusive instructions to MMIO space.
>> Sure, your CPU doesn't have RMW instructions -- how to emulate
>> those if you don't have them is a totally different thing.
> Let me say it more clearly: On ARM, it is impossible to perform atomic
> operations on MMIO space.

It's all completely beside the point, see the other subthread, but...

Yeah, you can't do LL/SC to MMIO space; ARM isn't alone in that.
You could still implement atomic operations on MMIO space by taking
a lock elsewhere, in normal cacheable memory space. Why you would
do this is a separate question, you probably don't want it :-)


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-08-21 16:59    [W:0.216 / U:14.944 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site