On Mon, Sep 03, 2001 at 01:27:02PM -0700, David Mosberger wrote:
> >> + if (!test_bit(PG_arch_1, &page->flags)) {
> >> + __flush_dcache_icache((unsigned long)kmap(page));
> >> + kunmap(page);
> >> + set_bit(PG_arch_1, &page->flags);
>
> Richard> Race. Use test_and_set_bit.
>
> Nope, the old code is correct: you must turn on PG_arch_1 *after*
> flushing the cache. Yes, you might sometimes double flush, but that's
> both safe and rare.
You can get a missed flush from
bit == 0
flush cache
modify page
bit = 0
bit = 1
unless this is protected from some outer lock of which
I am not aware.
I do see your point about the early set though.
r~
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This archive was generated by hypermail 2b29 : Fri Sep 07 2001 - 21:00:21 EST