tree 082b6e99d4067c107d5ee377fd96c6c082d7bba0
parent e48be50500da0ca5c6ad69ee1138e6d78d8a8be9
author Linus Torvalds <torvalds@linux-foundation.org> 1424475991 -0800
committer Karsten Tausche <karsten@fairphone.com> 1537870800 +0200

UPSTREAM: kernel: make READ_ONCE() valid on const arguments

The use of READ_ONCE() causes lots of warnings witht he pending paravirt
spinlock fixes, because those ends up having passing a member to a
'const' structure to READ_ONCE().

There should certainly be nothing wrong with using READ_ONCE() with a
const source, but the helper function __read_once_size() would cause
warnings because it would drop the 'const' qualifier, but also because
the destination would be marked 'const' too due to the use of 'typeof'.

Use a union of types in READ_ONCE() to avoid this issue.

Also make sure to use parenthesis around the macro arguments to avoid
possible operator precedence issues.

Tested-by: Ingo Molnar <mingo@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Issue: SEC-1289
Bug: 28705983
(cherry picked from commit dd36929720f40f17685e841ae0d4c581c165ea60)
Change-Id: I73b280cfae42245f6adf6a8e50be7f9177c88ebe
(cherry picked from commit 20a8b65f6540fa3088a256d8067c441f1f178b8e)