diff options
| author | Will Deacon <will.deacon@arm.com> | 2015-11-18 10:13:08 +0000 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2015-11-18 18:06:43 +0000 |
| commit | c139aa60c1007429335131167a0ca181e38c5668 (patch) | |
| tree | f4ab14648498f179be80c4b3091fbfc913bac074 /arch/arm64 | |
| parent | 0b2aa5b80bbf4d0fb5daa1fb83ff637daa12d552 (diff) | |
| download | linux-c139aa60c1007429335131167a0ca181e38c5668.tar.bz2 | |
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 <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>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64')
| -rw-r--r-- | arch/arm64/include/asm/barrier.h | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h index 624f9679f4b0..9622eb48f894 100644 --- a/arch/arm64/include/asm/barrier.h +++ b/arch/arm64/include/asm/barrier.h @@ -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) |