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AGP fix race condition between unmapping and freeing pages

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With Andi's clflush fixup, we were getting hangs on server exit, flushing the
mappings after freeing each page helped.

This showed up a race condition where the pages after being freed could be
reused before the agp mappings had been flushed.  Flushing after each single
page is a bad thing for future drm work, so make the page destroy a two pass
unmapping all the pages, flushing the mappings, and then destroying the pages.

Signed-off-by: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Dave Airlie
2007-10-15 10:19:16 +10:00
committed by Dave Airlie
parent 23fd50450a
commit a2721e998e
6 changed files with 48 additions and 27 deletions
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12
drivers/char/agp/backend.c
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@@ -189,9 +189,11 @@ static int agp_backend_initialize(struct agp_bridge_data *bridge)
err_out:
if (bridge->driver->needs_scratch_page) {
bridge->driver->agp_destroy_page(
gart_to_virt(bridge->scratch_page_real));
bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),
AGP_PAGE_DESTROY_UNMAP);
flush_agp_mappings();
bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),
AGP_PAGE_DESTROY_FREE);
}
if (got_gatt)
bridge->driver->free_gatt_table(bridge);
@@ -215,9 +217,11 @@ static void agp_backend_cleanup(struct agp_bridge_data *bridge)
if (bridge->driver->agp_destroy_page &&
bridge->driver->needs_scratch_page) {
bridge->driver->agp_destroy_page(
gart_to_virt(bridge->scratch_page_real));
bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),
AGP_PAGE_DESTROY_UNMAP);
flush_agp_mappings();
bridge->driver->agp_destroy_page(gart_to_virt(bridge->scratch_page_real),
AGP_PAGE_DESTROY_FREE);
}
}