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Peter Anvin" , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt Subject: Re: [PATCH v1 1/1] x86/percpu: Cast -1 to argument type when comparing in percpu_add_op() Message-ID: References: <20240905170356.260300-1-andriy.shevchenko@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240905170356.260300-1-andriy.shevchenko@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo X-Stat-Signature: dygtrmx3a8emgoijsg9m5gig7yqqy554 X-Rspamd-Queue-Id: 4CFD512001A X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1729085825-479033 X-HE-Meta: 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 MZlKYtUy N61DGdZHqSwutvcSW9/XbVg2JcXmp0PQiNVRvUzfDxf7guJ1qRmPnumuUQqJQMdQcvGqzFoS8wGZMtcspx5vKqEJNR4gFMd57zKTWmYVOZ9Cvd2fraQufn57Lg+BJMVZmDXeGai3n3kmQ3clKt60LrCju3M+t2bCXaL3BSFSaIySMLBbcpSmrC0g3VaXeOlct4ED7zWyb9WqE0fQwsDyIZr7qfsJ+WDyFRq4RSlwTbb7pSwP0PT2LGGcd/07Suaqz9uS+SIlO7NcGt0anscQwJ1EaPw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Sep 05, 2024 at 08:03:56PM +0300, Andy Shevchenko wrote: > When percpu_add_op() is used with unsigned argument, it prevents kernel builds > with clang, `make W=1` and CONFIG_WERROR=y: > > net/ipv4/tcp_output.c:187:3: error: result of comparison of constant -1 with expression of type 'u8' (aka 'unsigned char') is always false [-Werror,-Wtautological-constant-out-of-range-compare] > 187 | NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED, > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 188 | tp->compressed_ack); > | ~~~~~~~~~~~~~~~~~~~ > ... > arch/x86/include/asm/percpu.h:238:31: note: expanded from macro 'percpu_add_op' > 238 | ((val) == 1 || (val) == -1)) ? \ > | ~~~~~ ^ ~~ > > Fix this by casting -1 to the type of the parameter and then compare. Any comments? Or can it be taken in? -- With Best Regards, Andy Shevchenko