• Linus Torvalds's avatar
    kernel: make READ_ONCE() valid on const arguments · dd369297
    Linus Torvalds authored
    
    
    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: default avatarIngo Molnar <mingo@kernel.org>
    Cc: Christian Borntraeger <borntraeger@de.ibm.com>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    dd369297