MIPS: Compare __SYNC_loongson3_war against 0

When building with clang when CONFIG_CPU_LOONGSON3_WORKAROUNDS is
enabled:

 In file included from lib/errseq.c:4:
 In file included from ./include/linux/atomic.h:7:
 ./arch/mips/include/asm/atomic.h:52:1: warning: converting the result of
 '<<' to a boolean always evaluates to true
 [-Wtautological-constant-compare]
 ATOMIC_OPS(atomic64, s64)
 ^
 ./arch/mips/include/asm/atomic.h:40:9: note: expanded from macro
 'ATOMIC_OPS'
         return cmpxchg(&v->counter, o, n);
                ^
 ./arch/mips/include/asm/cmpxchg.h:194:7: note: expanded from macro
 'cmpxchg'
         if (!__SYNC_loongson3_war)
              ^
 ./arch/mips/include/asm/sync.h:147:34: note: expanded from macro
 '__SYNC_loongson3_war'
 # define __SYNC_loongson3_war   (1 << 31)
                                    ^

While it is not wrong that the result of this shift is always true in a
boolean context, it is not a problem here. Regardless, the warning is
really noisy so rather than making the shift a boolean implicitly, use
it in an equality comparison so the shift is used as an integer value.

Fixes: 4d1dbfe6cbec ("MIPS: atomic: Emit Loongson3 sync workarounds within asm")
Fixes: a91f2a1dba44 ("MIPS: cmpxchg: Omit redundant barriers for Loongson3")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

diff --git a/arch/mips/include/asm/atomic.h b/arch/mips/include/asm/atomic.h
index f904084fcb1fd3510101d0ef1b3810031332d488..27ad767915390c5ce914cad99c3755f22b9b7bdc 100644 (file)
--- a/arch/mips/include/asm/atomic.h
+++ b/arch/mips/include/asm/atomic.h
@@ -248,7 +248,7 @@ static __inline__ int pfx##_sub_if_positive(type i, pfx##_t * v)    \
         * bltz that can branch to code outside of the LL/SC loop. As   \
         * such, we don't need to emit another barrier here.            \
         */                                                             \
-       if (!__SYNC_loongson3_war)                                      \
+       if (__SYNC_loongson3_war == 0)                                  \
                smp_mb__after_atomic();                                 \
                                                                        \
        return result;                                                  \

diff --git a/arch/mips/include/asm/cmpxchg.h b/arch/mips/include/asm/cmpxchg.h
index 5b0b3a6777ea518489de75606560fdf2e4a14d1d..ed8f3f3c4304a2ec9a8d9e3d155735da3bf88744 100644 (file)
--- a/arch/mips/include/asm/cmpxchg.h
+++ b/arch/mips/include/asm/cmpxchg.h
@@ -99,7 +99,7 @@ unsigned long __xchg(volatile void *ptr, unsigned long x, int size)
         * contains a completion barrier prior to the LL, so we don't   \
         * need to emit an extra one here.                              \
         */                                                             \
-       if (!__SYNC_loongson3_war)                                      \
+       if (__SYNC_loongson3_war == 0)                                  \
                smp_mb__before_llsc();                                  \
                                                                        \
        __res = (__typeof__(*(ptr)))                                    \
@@ -191,7 +191,7 @@ unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
         * contains a completion barrier prior to the LL, so we don't   \
         * need to emit an extra one here.                              \
         */                                                             \
-       if (!__SYNC_loongson3_war)                                      \
+       if (__SYNC_loongson3_war == 0)                                  \
                smp_mb__before_llsc();                                  \
                                                                        \
        __res = cmpxchg_local((ptr), (old), (new));                     \
@@ -201,7 +201,7 @@ unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
         * contains a completion barrier after the SC, so we don't      \
         * need to emit an extra one here.                              \
         */                                                             \
-       if (!__SYNC_loongson3_war)                                      \
+       if (__SYNC_loongson3_war == 0)                                  \
                smp_llsc_mb();                                          \
                                                                        \
        __res;                                                          \