Re: [Qemu-devel] [RFC PATCH] target-arm: protect cpu_exclusive_*.

[Peter Maydell]

On 17 December 2014 at 11:25, Paolo Bonzini <address@hidden> wrote:
>
>
> On 17/12/2014 12:18, Alexander Graf wrote:
>>
>> So I think the best way to go forward would be to add transaction_start
>> and transaction_end opcodes to TCG and implement them as mutex locks
>> today. When you get the chance to get yourself a machine that supports
>> actual TM, try to replace them with transaction start/end blocks and
>> have the normal mutex code as fallback if the transaction fails.
>
> Or implement load_locked/store_conditional TCG ops.  They can be
> implemented as transactions, hardware ll/sc, or something slow that uses
> the MMU.

You'd need to compare the semantics of ll/sc across the various
architectures to find out if there was anything you could
actually meaningfully define as useful TCG op semantics there.

-- PMM