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mm/hmm: Remove racy protection against double-unregistration 

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>
This commit is contained in:
Jason Gunthorpe 2019-05-23 11:31:45 -03:00
parent 8a1a0cd0b7
commit 187229c2dd
1 changed files with 1 additions and 7 deletions
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8
mm/hmm.c
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@ -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);