Messages in this thread | | | Date | Mon, 21 Nov 2011 17:02:44 +0100 | From | Daniel Vetter <> | Subject | Re: [Intel-gfx] [PATCH 02/13] drm/i915: rewrite shmem_pwrite_slow to use copy_from_user |
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On Sun, Nov 20, 2011 at 09:56:32PM -0800, Ben Widawsky wrote: [snip the patch] > Bikeshed, but I would much prefer a #define for the swizzle > bit/cacheline size.
I've looked at this stuff way too long, so I'm biased, but 64 = cacheline = dram fetch size = 1 << 64 feels about as natural for me as 4096 = PAGE_SIZE ...
[snip the patch]
> I must be missing something obvious here... > Can you explain how this can possibly be considered safe without holding > struct_mutex?
That's the reason why the commit msg goes through every case and explains why I think it's safe. The large thing here is that we need to drop the mutex when calling copy_*_user (at least in the non-atomic slow-paths) because otherwise we might deadlock with our own pagefault handler. -Daniel -- Daniel Vetter Mail: daniel@ffwll.ch Mobile: +41 (0)79 365 57 48
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