Re: must-fix list for 2.6.0

Andrew Morton
2003-04-30T23:50:03Z

viro@parcelfarce.linux.theplanet.co.uk wrote:
>
> On Wed, Apr 30, 2003 at 04:21:08PM -0700, Andrew Morton wrote:
> > menu if there was a kernel build happening at the same time. That is just
> > utterly broken, so if we're going to leave the sched.c code as-is then we
> > *require* that all applications be updated to not spin on sched_yield.
>
> Excuse me, but WTF do they spin on the sched_yield() in the first place?
> _That_ sounds like utterly broken...

I think it's happening down inside the old linuxthreads library. No idea
who, what, where or why.

There are quite a few places in the kernel which do it, too. Usually when
waiting for memory to come free. These are being gradually removed, in
favour of blk_congestion_wait() calls.

That leaves behind the very performance-critical sched_yield() in ext3
transaction batching. That was designed to allow other processes to join a
transaction before the calling one closes the transaction. With the new
yield() it was causing horrid starvation and was lamely replaced with a
schedule(). It needs to be resurrected for real, but I'm not sure how.
Probably just a sleep(0.01).