@@ -64,27 +64,31 @@ do { \
#define smp_load_acquire(p) \
({ \
- typeof(*p) ___p1; \
+ union { typeof(*p) __val; char __c[1]; } __u; \
compiletime_assert_atomic_type(*p); \
switch (sizeof(*p)) { \
case 1: \
asm volatile ("ldarb %w0, %1" \
- : "=r" (___p1) : "Q" (*p) : "memory"); \
+ : "=r" (*(__u8 *)__u.__c) \
+ : "Q" (*p) : "memory"); \
break; \
case 2: \
asm volatile ("ldarh %w0, %1" \
- : "=r" (___p1) : "Q" (*p) : "memory"); \
+ : "=r" (*(__u16 *)__u.__c) \
+ : "Q" (*p) : "memory"); \
break; \
case 4: \
asm volatile ("ldar %w0, %1" \
- : "=r" (___p1) : "Q" (*p) : "memory"); \
+ : "=r" (*(__u32 *)__u.__c) \
+ : "Q" (*p) : "memory"); \
break; \
case 8: \
asm volatile ("ldar %0, %1" \
- : "=r" (___p1) : "Q" (*p) : "memory"); \
+ : "=r" (*(__u64 *)__u.__c) \
+ : "Q" (*p) : "memory"); \
break; \
} \
- ___p1; \
+ __u.__val; \
})
#define read_barrier_depends() do { } while(0)
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 <arnd@arndb.de> Cc: David Daney <david.daney@cavium.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Reported-by: Arnd Bergmann <arnd@arndb.de> Reported-by: David Daney <david.daney@cavium.com> Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm64/include/asm/barrier.h | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) -- 2.1.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel