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SubjectRe: [PATCH 1/2] sched/wait: Break up long wake list walk
On Tue, Aug 22, 2017 at 01:42:13PM -0700, Linus Torvalds wrote:
> +void wait_on_page_bit_or_yield(struct page *page, int bit_nr)
> +{
> + if (PageWaiters(page)) {
> + yield();
> + return;
> + }
> + wait_on_page_bit(page, bit_nr);
> +}

So _the_ problem with yield() is when you hit this with a RT task it
will busy spin and possibly not allow the task that actually has the
lock to make progress at all.

So ideally there'd be a timeout or other limit on the amount of yield().

This being bit-spinlocks leaves us very short on state to play with
though :/

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