On 6/6/19 11:44 AM, Jason Gunthorpe wrote:
From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
No other register/unregister kernel API attempts to provide this kind of
protection as it is inherently racy, so just drop it.
Callers should provide their own protection, it appears nouveau already
does, but just in case drop a debugging POISON.
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
---
mm/hmm.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)
diff --git a/mm/hmm.c b/mm/hmm.c
index c702cd72651b53..6802de7080d172 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -284,18 +284,13 @@ EXPORT_SYMBOL(hmm_mirror_register);
*/
void hmm_mirror_unregister(struct hmm_mirror *mirror)
{
- struct hmm *hmm = READ_ONCE(mirror->hmm);
-
- if (hmm == NULL)
- return;
+ struct hmm *hmm = mirror->hmm;
down_write(&hmm->mirrors_sem);
list_del_init(&mirror->list);
- /* To protect us against double unregister ... */
- mirror->hmm = NULL;
up_write(&hmm->mirrors_sem);
-
hmm_put(hmm);
+ memset(&mirror->hmm, POISON_INUSE, sizeof(mirror->hmm));
}
EXPORT_SYMBOL(hmm_mirror_unregister);
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