[concurrency-interest] JLS 17.7 Non-atomic treatment of double and long : Android

Vitaly Davidovich vitalyd at gmail.com
Mon Apr 29 19:41:04 EDT 2013


No different than x86.  I suppose story will be different with armv8 and
dalvik support for it.

Sent from my phone
On Apr 29, 2013 4:45 PM, "Aleksey Shipilev" <aleksey.shipilev at oracle.com>
wrote:

> On 04/30/2013 12:27 AM, Tim Halloran wrote:
> > Does anyone know if Android's Dalvik goes with the recommendation in JLS
> > 17.7 and avoids splitting 64-bit values. I'm pretty sure most other VMs
> do.
>
> You might safely assume ARM does not have full-width 64-bit reads/writes
> (it can emulate atomic read/write with LL/SC-ed loop), so I'm pretty
> sure non-volatile longs are not atomic on most mobile platforms.
>
> > After some searching I couldn't find any information and it seems pretty
> > hard to write code to "test" for this on the VM.
>
> It is actually one of the simplest tests for concurrency, and simple
> enough to reproduce in the wild.
>
> -Aleksey.
>
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