atomic operations

[Arun KS]

Hi Peter,

On Sun, Feb 24, 2013 at 6:20 PM, Peter Teoh <htmldeveloper at gmail.com> wrote:
> in simple terms, any operation, in terms assembly instructions, which can be
> executed in ONE instruction, is "atomic", because, just like an atom, it
> cannot be broken up into parts.   any instructions that is longer than one,
> for eg, TWO instruction, is NOT atomic, because in BETWEEN the first and 2nd
> instruction, something like an interrupt can come in, and affect the values
> of the operand when it is passed from instruction one to second instruction.

Nice explanation.

Thanks,
Arun
> To save me from reiteration:
>
> http://www.ibm.com/developerworks/library/pa-dalign/ (search for
> "atomicity").
>
> http://stackoverflow.com/questions/381244/purpose-of-memory-alignment
>
> http://lwn.net/Articles/260832/
>
> http://www.songho.ca/misc/alignment/dataalign.html
>
> http://www.cis.upenn.edu/~palsetia/cit595s08/Lectures08/alignmentOrdering.pdf
>
> Essentially, atomicity and non-alignment become problematic when u tried to
> to read using non-byte addressing mode with non-aligned address.
>
> On Sun, Feb 24, 2013 at 5:42 PM, Shraddha Kamat <sh2008ka at gmail.com> wrote:
>>
>> what is the relation between atomic operations and memory alignment ?
>>
>> I read from UTLK that "an unaligned memory access is not atomic"
>>
>> please explain me , I am not able to get the relationship between
>> memory alignment and atomicity of the operation.
>>
>>
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>
>
>
>
> --
> Regards,
> Peter Teoh
>
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