Re: [PATCH] fix gettimeofday vs. update_gtod race

On Wed, 2006-08-16 at 19:18 -0500, Nathan Lynch wrote:

No?  I didn't find anything about mftb having synchronizing
behavior.  How should we ensure that temp_varp is assigned before
reading the timebase?

I sync an isync would be enough.

Surely at least a compiler barrier is needed?

Yeah.

quoted

and the race not completely closed imho... 

How so?  I could've missed something, but I've hammered the patch
pretty hard, fwiw.

Nah you are right, but you may be using a too big hammer

quoted

I need to think about it a bit more closely but what about instead
just check if tb_ticks goes negative, and if yes, just do get_tb()
again ?  That might be faster than having a sync in there and should
still be correct.

I did try something like that but found that a loop (i.e. multiple
get_tb's to "catch up") was necessary.

Hrm... even with an isync ?

Ben.