On Tue, 05 Apr 2022, Trond Myklebust wrote:
> On Mon, 2022-04-04 at 15:34 +0000, Chuck Lever III wrote:
> >
....
> >
> > I gotta ask: Why does cache_defer_req() check if thread_wait is zero?
> > Is there some code in the kernel now that sets it to zero? I see only
> > these two values:
> >
> > 784 if (!test_bit(SP_CONGESTED, &pool->sp_flags))
> > 785 rqstp->rq_chandle.thread_wait = 5*HZ;
> > 786 else
> > 787 rqstp->rq_chandle.thread_wait = 1*HZ;
>
>
> That test goes all the way back to commit f16b6e8d838b ("sunrpc/cache:
> allow threads to block while waiting for cache update."), so probably
> more of a question for Neil.
12 years ago.... the commit message suggests that the "underlying
transport" might not approve of sleeping, but I cannot think what that
might mean. Probably it seemed to mean something earlier in the design
process but I discarded the idea without discarding the code.
> I don't see any immediate problems with removing it: even if someone
> does set a value of 0, the wait code itself should cope.
>
Agreed.
NeilBrown
