On Thu, Sep 27, 2001 at 05:03:49PM -0700, Linus Torvalds wrote:
> On Fri, 28 Sep 2001, Andrea Arcangeli wrote:
> > Moving clear_bit just above submit_bh will fix it (please Robert make
> > this change before testing it), because if we block in submit_bh in the
> > bounce, then we won't deadlock on ourself because of the pagehighmem
> > check
> We won't block on _ourselves_, but we can block on _two_ people doing it,
If other people waits for us it's ok (if they waits it means they're not
using GFP_NOIO and they're also not using GFP_NOHIGHIO).
We cannot wait on other two people doing it since they would be highmem
pages and the pagehighmem check forbids that.
> and blocking on each others requests that are blocked waiting on a bounce
> buffer. Both will have one locked buffer, both will be waiting for the
> other person unlocking that buffer, and neither will ever make progress.
> You could clear that bit _after_ the bounce buffer allocation, I suspect.
I don't think it's necessary.
> But I also suspect that it doesn't matter much, and as I can imagine
> similar problems with GFP_NOIO and loopback etc (do you see any reason why
> loopback couldn't deadlock on waiting for itself?), I think the GFP_XXX
> thing is the proper fix.
GFP_NOIO is a no brainer, it cannot go wrong see the other email.
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This archive was generated by hypermail 2b29 : Sun Sep 30 2001 - 21:00:59 EST