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authorAndrea Arcangeli <aarcange@redhat.com>2019-05-15 00:40:50 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-15 04:52:47 +0200
commit987717e5e016a0dd3011d3bb16546672713f94e2 (patch)
treefa83028052001ed851507f8a42b241ba45212b20 /kernel/exit.c
parentuserfaultfd: use RCU to free the task struct when fork fails (diff)
downloadlinux-987717e5e016a0dd3011d3bb16546672713f94e2.tar.xz
linux-987717e5e016a0dd3011d3bb16546672713f94e2.zip
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>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r--kernel/exit.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 2166c2d92ddc..8361a560cd1d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -422,7 +422,7 @@ retry:
* freed task structure.
*/
if (atomic_read(&mm->mm_users) <= 1) {
- mm->owner = NULL;
+ WRITE_ONCE(mm->owner, NULL);
return;
}
@@ -462,7 +462,7 @@ retry:
* most likely racing with swapoff (try_to_unuse()) or /proc or
* ptrace or page migration (get_task_mm()). Mark owner as NULL.
*/
- mm->owner = NULL;
+ WRITE_ONCE(mm->owner, NULL);
return;
assign_new_owner:
@@ -483,7 +483,7 @@ assign_new_owner:
put_task_struct(c);
goto retry;
}
- mm->owner = c;
+ WRITE_ONCE(mm->owner, c);
task_unlock(c);
put_task_struct(c);
}