On Sat, 15 Sep 2007 03:41:26 -0700 Andrew Morton
<[email protected]> wrote:
> eww, kmap. Large amounts of them, apparently.
>
> Be aware that kmap is a) slow and b) deadlockable. The latter happens when
> multiple tasks want to take more than one kmap simultaneously: they all
> wait for someone else to release one. Your code here seems especially
> vulnerable to this.
>
> Nick had a kmap-speedup patchset a while back which addressed a) but I
> don't know if it addressed the deadlock. But that patch seemed to die.
That would've been me.
What I did to address b) is to pre-allocate each kmap user a second
kmap slot. Of course this isn't water-tight either.
These patches are part of -rt, I could respin against mainline if there
is interest.
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