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    SubjectRe: must-fix list for 2.6.0
    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).

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