From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yury Norov Date: Fri, 15 Jul 2022 14:19:12 +0000 Subject: Re: [PATCH v5 6/9] bitops: let optimize out non-atomic bitops on compile-time constants Message-Id: List-Id: References: <20220624121313.2382500-1-alexandr.lobakin@intel.com> <20220624121313.2382500-7-alexandr.lobakin@intel.com> <20220715000402.GA512558@roeck-us.net> <20220715132633.61480-1-alexandr.lobakin@intel.com> <8c949bd4-d25a-d5f5-49be-59d52e4b6c9d@roeck-us.net> In-Reply-To: <8c949bd4-d25a-d5f5-49be-59d52e4b6c9d@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Guenter Roeck Cc: Alexander Lobakin , Arnd Bergmann , Andy Shevchenko , Mark Rutland , Matt Turner , Brian Cain , Geert Uytterhoeven , Yoshinori Sato , Rich Felker , "David S. Miller" , Kees Cook , "Peter Zijlstra (Intel)" , Marco Elver , Borislav Petkov , Tony Luck , Maciej Fijalkowski , Jesse Brandeburg , Greg Kroah-Hartman , Nathan Chancellor , Nick Desaulniers , Tom Rix , kernel test robot , linux-alpha@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, llvm@lists.linux.dev, linux-kernel@vger.kernel.org On Fri, Jul 15, 2022 at 06:49:46AM -0700, Guenter Roeck wrote: > On 7/15/22 06:26, Alexander Lobakin wrote: > > From: Guenter Roeck > > Date: Thu, 14 Jul 2022 17:04:02 -0700 > > > > > On Fri, Jun 24, 2022 at 02:13:10PM +0200, Alexander Lobakin wrote: > > > > Currently, many architecture-specific non-atomic bitop > > > > implementations use inline asm or other hacks which are faster or > > > > [...] > > > > > > Cc: Mark Rutland > > > > Signed-off-by: Alexander Lobakin > > > > Reviewed-by: Marco Elver > > > > > > Building i386:allyesconfig ... failed > > > -------------- > > > Error log: > > > arch/x86/platform/olpc/olpc-xo1-sci.c: In function 'send_ebook_state': > > > arch/x86/platform/olpc/olpc-xo1-sci.c:83:63: error: logical not is only applied to the left hand side of comparison > > > > Looks like a trigger, not a cause... Anyway, this construct: > > > > unsigned char state; > > > > [...] > > > > if (!!test_bit(SW_TABLET_MODE, ebook_switch_idev->sw) = state) > > > > doesn't look legit enough. > > That redundant double-negation [of boolean value], together with > > comparing boolean to char, provokes compilers to think the author > > made logical mistakes here, although it works as expected. > > Could you please try (if it's not automated build which you can't > > modify) the following: > > > > Agreed, the existing code seems wrong. The change below looks correct > and fixes the problem. Feel free to add > > Reviewed-and-tested-by: Guenter Roeck > > to the real patch. > > Thanks, > Guenter > > > --- a/arch/x86/platform/olpc/olpc-xo1-sci.c > > +++ b/arch/x86/platform/olpc/olpc-xo1-sci.c > > @@ -80,7 +80,7 @@ static void send_ebook_state(void) > > return; > > } > > - if (!!test_bit(SW_TABLET_MODE, ebook_switch_idev->sw) = state) > > + if (test_bit(SW_TABLET_MODE, ebook_switch_idev->sw) = !!state) > > return; /* Nothing new to report. */ > > input_report_switch(ebook_switch_idev, SW_TABLET_MODE, state); > > --- > > > > We'd take it into the bitmap tree then. The series revealed > > a fistful of existing code issues already :) Would you like me to add your signed-off-by and apply, or you prefer to send it out as a patch? Thanks, Yury