[CRIU] ARMv5 implementation counter value

[Maikel Coenen]

On 04/04/2019, 14:44, "Cyrill Gorcunov" <gorcunov at gmail.com> wrote:

 >   On Thu, Apr 04, 2019 at 12:37:04PM +0000, Maikel Coenen wrote:
 >   > Hi,
 >  > 
 >   > I am almost done with implementing ARMv5 implementation of CRIU but currently
 >   > stuck at researching the input arguments of the function atomic_add_return and
 >   > atomic_sub_return.
 >   >
 >   > These functions make use of the atomic_t struct with a counter in it but I want
 >   > to know what possible values this counter can be, so I can make some kind
 >   > of mutex for it.
 >   > 
 >   > Can someone help me with this question?
 >   
 >   Not sure I understand your question. Counters are integer values as far as I
 >   remember, the only trick is to use lock prefix on instructions generated so
 >   they won't be modified simultaneously on smp machines. Probably you should
 >   look into linux kernel arch/ directory, usually atomic helpers are sitting
 >   there.

True, but ARMv5 does not implement any lock prefix or exclusive load/store so you have to implement that yourself.
The counter integer, does it have any range of numbers it usually takes? Or for what purpose are these functions implemented?