Deform brush and deadlocks

Boudewijn Rempt boud at
Mon Jun 29 15:37:42 CEST 2009

On Mon, 29 Jun 2009, Dmitry Kazakov wrote:

> Hi, Lukas!
> Thanks for the change! I'm not sure it'll help to the current engine, but
> it'll really help when i make a working read-write lock.
> About sampled methods:
> i guess these conditions are never true =)
> floor(x) <= x
> 0 <= x-floor(x)
> 2all:
> It seems that old engine didn't have any exclusive access to tiles (am i
> right?). Btw, is this exclusive access needed really?
> In the case of deform brush, KisTopDownUpdateStrategy was requesting read
> access only, so this very problem will be solved by read/write lock.
> But i wonder whether there is any possibility in Krita that two separate
> threads would request write access to one tile simultaneously? Casper said
> there was (is) some "the drying filter for watercolors" that can cause it.
> Is it still applicable to current Krita?

The drying filter isn't around anymore, although something similar might return.
In general, I think it is a good thing to assume that there will be occasions when
two threads try to get write access on the same tile, even if that shouldn't


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