arm64: barriers: fix smp_load_acquire to work with const arguments

A newly introduced function in include/net/sock.h passes a const
argument to smp_load_acquire:

  static inline int sk_state_load(const struct sock *sk)
  {
	return smp_load_acquire(&sk->sk_state);
  }

This cause an allmodconfig build failure, since our underlying
load-acquire implementation does not handle const types correctly:

  include/net/sock.h: In function 'sk_state_load':
  ./arch/arm64/include/asm/barrier.h:71:3: error: read-only variable '___p1' used as 'asm' output
     asm volatile ("ldarb %w0, %1"    \

This patch fixes the problem by reusing the trick in READ_ONCE that
loads via a non-const member of an anonymous union. This has the
advantage of allowing us to use smp_load_acquire on packed structures
(e.g. arch_spinlock_t) as well as primitive types.

Cc: Arnd Bergmann <[email protected]>
Cc: David Daney <[email protected]>
Cc: Eric Dumazet <[email protected]>
Reported-by: Arnd Bergmann <[email protected]>
Reported-by: David Daney <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Catalin Marinas <[email protected]>

0 files changed, 0 insertions, 0 deletions