On Sun, Mar 10, 2019 at 1:20 AM Mathias Fröhlich <mathias.froehl...@gmx.net> wrote:
> Brian, > > One question also for my own education inline below: > > On Friday, 8 March 2019 23:52:09 CET Brian Paul wrote: > > After a while of running google-chrome and viewing Bing maps, we'd see > > "context mismatch in svga_sampler_view_destroy()" messages and > > eventually crash because we leaked too many sampler views (the kernel > > module would have too many sampler views). > > > > When a texture object is being deleted, we call > > st_texture_release_all_sampler_views() to release all the sampler > > views. In the list, there may sampler views which were created from > > other contexts. > > > > Previously, we called pipe_sampler_view_release(pipe, view) which would > > use the given pipe context to destroy the view if the refcount hit > > zero. The svga error was triggered because we were calling > > pipe->sampler_view_destroy(pipe, view) and the pipe context didn't > > match the view's parent context. > > > > Instead, call pipe_sampler_reference(&view, NULL). That way, if > > the refcount hits zero, we'll use the view's parent context to > > destroy the view. That's what we want. > > That sounds plausible so far. > > What I wonder, is calling into an 'arbitrary' different context and do > work there > thread safe for any gallium driver? > Right. Before this patch there was the problem of trying to destroy a sampler view with a context different from the one which created it. That's fixed, but now there's the multi-threading issue as you say, and which I believe, is a less-common situation. > > Especially since pipe_sampler_view_reference in its documentation says > that the > views provided need to originate from the same context and that this must > be the 'current'. > > I have been taking a quick look into iris and radeonsi and both seem to be > safe > in terms of threads for dereferencing the views finally. > But either the documentation of pipe_sampler_view_reference should be > updated > or I may miss an other piece of the puzzle to see that it is still save to > do so. > Last week I posted a patch series for the VMware driver which handled the thread issue with a list of "zombie" sampler views. Jose suggested moving that up into the state tracker, and that is a better long-term solution. I'm almost done with a patch series that does that. I'll likely post it tomorrow. -Brian
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