diff mbox series

[14/22] mm/hmm: Remove racy protection against double-unregistration

Message ID 20190701062020.19239-15-hch@lst.de (mailing list archive)
State New, archived
Headers show
Series [01/22] mm/hmm.c: suppress compilation warnings when CONFIG_HUGETLB_PAGE is not set | expand

Commit Message

Christoph Hellwig July 1, 2019, 6:20 a.m. UTC 
From: Jason Gunthorpe <jgg@mellanox.com>

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, and it appears nouveau
already does.

Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Philip Yang <Philip.Yang@amd.com>
---
 mm/hmm.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/mm/hmm.c b/mm/hmm.c
index 6f5dc6d568fe..2ef14b2b5505 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -276,17 +276,11 @@  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);
 }
 EXPORT_SYMBOL(hmm_mirror_unregister);