Re: [patch] sched: fix scheduling latencies for !PREEMPT kernels

Lee Revell
2004-09-15T02:00:42Z

On Tue, 2004-09-14 at 21:46, William Lee Irwin III wrote:
> On Tue, Sep 14, 2004 at 08:22:29PM -0400, Lee Revell wrote:
> > Although, there is at least one case (reiser3) where we know which data
> > structures the BKL is supposed to be protecting, because the code does
> > something like reiserfs_write_lock(foo_data_structure) which gets
> > define'd away to lock_kernel(). And apparently some of the best and
> > brightest on LKML have tried and failed to fix it, and even Hans says
> > "it's HARD, the fix is reiser4".
> > So, maybe some of the current uses should be tagged as WONTFIX.
>
> I've not heard a peep about anyone trying to fix this. It should be
> killed off along with the rest, of course, but like I said before, it's
> the messiest, dirtiest, and ugliest code that's left to go through,
> which is why it's been left for last. e.g. driver ->ioctl() methods.
>

Andrew tried to fix this a few times in 2.4 and it broke the FS in
subtle ways. Don't have an archive link but the message is
<20040712163141.31ef1ad6.akpm@osdl.org>. I asked Hans directly about it
and he said "balancing makes it hard, the fix is reiser4", see
<411925FA.2000303@namesys.com>.

Lee