From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
clang-built-linux@googlegroups.com,
kernel test robot <lkp@intel.com>
Subject: Re: [PATCH] MIPS: Compare __SYNC_loongson3_war against 0
Date: Fri, 15 Jan 2021 15:39:01 +0100 [thread overview]
Message-ID: <20210115143901.GB15166@alpha.franken.de> (raw)
In-Reply-To: <20210114173416.738455-1-natechancellor@gmail.com>
On Thu, Jan 14, 2021 at 10:34:16AM -0700, Nathan Chancellor wrote:
> 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>
> ---
> arch/mips/include/asm/atomic.h | 2 +-
> arch/mips/include/asm/cmpxchg.h | 6 +++---
> 2 files changed, 4 insertions(+), 4 deletions(-)
applied ti mips-next.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
prev parent reply other threads:[~2021-01-15 14:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 17:34 [PATCH] MIPS: Compare __SYNC_loongson3_war against 0 Nathan Chancellor
2021-01-14 17:48 ` Nick Desaulniers
2021-01-15 14:39 ` Thomas Bogendoerfer [this message]
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