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Since the gem pagefault handler relocks the vm object lock, other

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thread might fault on the same GTT offset meantime and instantiate the
mapping.  Recheck that the mgt device object still does not have a
page at the current offset after relocking, and return a possibly
installed page.

Reported by:	Oleg Sidorkin <osidorkin@gmail.com>
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2013-06-18 20:02:52 +00:00
parent 8b73dbd71f
commit aec577b8d1
1 changed files with 19 additions and 1 deletions
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20
sys/dev/drm2/i915/i915_gem.c
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@ -1371,6 +1371,23 @@ unlocked_vmobj:
} else
DRM_LOCK(dev);
/*
* Since the object lock was dropped, other thread might have
* faulted on the same GTT address and instantiated the
* mapping for the page. Recheck.
*/
VM_OBJECT_WLOCK(vm_obj);
m = vm_page_lookup(vm_obj, OFF_TO_IDX(offset));
if (m != NULL) {
if ((m->flags & VPO_BUSY) != 0) {
DRM_UNLOCK(dev);
vm_page_sleep(m, "915pee");
goto retry;
}
goto have_page;
} else
VM_OBJECT_WUNLOCK(vm_obj);
/* Now bind it into the GTT if needed */
if (!obj->map_and_fenceable) {
ret = i915_gem_object_unbind(obj);
@ -1424,8 +1441,9 @@ unlocked_vmobj:
goto retry;
}
m->valid = VM_PAGE_BITS_ALL;
*mres = m;
vm_page_insert(m, vm_obj, OFF_TO_IDX(offset));
have_page:
*mres = m;
vm_page_busy(m);
CTR4(KTR_DRM, "fault %p %jx %x phys %x", gem_obj, offset, prot,