On Wed Apr 20 11:02:30 2016, muks wrote:
> On Wed Apr 20 10:00:21 2016, muks wrote:
> > There's a race in the adaptive rwlock implementation in read and
> > update of rwl->spins.
> 
> The new code seems to use ISC_PLATFORM_BUSYWAITNOP which seems to be
> defined as "rep; nop" for x86 and x86_64.
> 
> rep is an instruction prefix that repeats the next instruction ecx
> times, decrementing ecx at each step. So ecx ought to be set to some
> deterministic value for it (what is its value here?). Also it clobbers
> ecx here.. is that fine?

Francis pointed out that the rep prefix does not apply to the nop instruction - the opcode sequence is used as the "pause" instruction.
So this part of the bug report is bogus.

The part about the race condition in rwl->spins still exists.