AGP fix race condition between unmapping and freeing pages
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>
diff --git a/drivers/char/agp/generic.c b/drivers/char/agp/generic.c
index 3db4f40..64b2f6d 100644
--- a/drivers/char/agp/generic.c
+++ b/drivers/char/agp/generic.c
@@ -195,9 +195,12 @@
}
if (curr->page_count != 0) {
for (i = 0; i < curr->page_count; i++) {
- curr->bridge->driver->agp_destroy_page(gart_to_virt(curr->memory[i]));
+ curr->bridge->driver->agp_destroy_page(gart_to_virt(curr->memory[i]), AGP_PAGE_DESTROY_UNMAP);
}
flush_agp_mappings();
+ for (i = 0; i < curr->page_count; i++) {
+ curr->bridge->driver->agp_destroy_page(gart_to_virt(curr->memory[i]), AGP_PAGE_DESTROY_FREE);
+ }
}
agp_free_key(curr->key);
agp_free_page_array(curr);
@@ -1176,7 +1179,7 @@
EXPORT_SYMBOL(agp_generic_alloc_page);
-void agp_generic_destroy_page(void *addr)
+void agp_generic_destroy_page(void *addr, int flags)
{
struct page *page;
@@ -1184,10 +1187,14 @@
return;
page = virt_to_page(addr);
- unmap_page_from_agp(page);
- put_page(page);
- free_page((unsigned long)addr);
- atomic_dec(&agp_bridge->current_memory_agp);
+ if (flags & AGP_PAGE_DESTROY_UNMAP)
+ unmap_page_from_agp(page);
+
+ if (flags & AGP_PAGE_DESTROY_FREE) {
+ put_page(page);
+ free_page((unsigned long)addr);
+ atomic_dec(&agp_bridge->current_memory_agp);
+ }
}
EXPORT_SYMBOL(agp_generic_destroy_page);
