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mm: change mm_update_next_owner() to update mm->owner with WRITE_ONCE
The RCU reader uses rcu_dereference() inside rcu_read_lock critical sections, so the writer shall use WRITE_ONCE. Just a cleanup, we still rely on gcc to emit atomic writes in other places. Link: http://lkml.kernel.org/r/20190325225636.11635-3-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@mellanox.com> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Xu <peterx@redhat.com> Cc: zhong jiang <zhongjiang@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -422,7 +422,7 @@ retry:
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* freed task structure.
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*/
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if (atomic_read(&mm->mm_users) <= 1) {
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mm->owner = NULL;
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WRITE_ONCE(mm->owner, NULL);
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return;
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}
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@ -462,7 +462,7 @@ retry:
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* most likely racing with swapoff (try_to_unuse()) or /proc or
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* ptrace or page migration (get_task_mm()). Mark owner as NULL.
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*/
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mm->owner = NULL;
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WRITE_ONCE(mm->owner, NULL);
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return;
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assign_new_owner:
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@ -483,7 +483,7 @@ assign_new_owner:
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put_task_struct(c);
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goto retry;
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}
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mm->owner = c;
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WRITE_ONCE(mm->owner, c);
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task_unlock(c);
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put_task_struct(c);
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}
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