Re: [PATCH] fs-writeback: drop wb->list_lock during blk_finish_plug()

From: Peter Zijlstra
Date: Mon Sep 28 2015 - 10:48:15 EST

On Fri, Sep 18, 2015 at 09:12:38AM -0700, Linus Torvalds wrote:
> So I disagree with your notion that it's a recursion flag. It is
> absolutely nothing of the sort.

OK, agreed. I had it classed under recursion in my head, clearly I
indexed it sloppily. In any case I have a patch that kills off

I just have to clean it up, benchmark, split and write changelogs. But
it should be forthcoming 'soon'. As is, it boots..

> It gets set by preemption - and,
> somewhat illogically, by cond_resched().

I suspect that was done to make cond_resched() (voluntary preemption)
more robust and only have a single preemption path/logic. But all that
was done well before I got involved.
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