linux-kernel - Re: [kbuild-all] Re: kernel/time/clocksource-wdtest.c:47:22: warning: signed shift result (0x27BC86B00) requires 35 bits to represent, but 'long' only has 32 bits

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Message-ID: <a10605cb-8de4-9da3-bda7-04f82e6fabe7@intel.com>
Date:   Tue, 6 Jul 2021 08:11:07 +0800
From:   Rong Chen <rong.a.chen@...el.com>
To:     paulmck@...nel.org
Cc:     kernel test robot <lkp@...el.com>,
        clang-built-linux@...glegroups.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [kbuild-all] Re: kernel/time/clocksource-wdtest.c:47:22: warning:
 signed shift result (0x27BC86B00) requires 35 bits to represent, but 'long'
 only has 32 bits



On 7/5/21 11:21 PM, Paul E. McKenney wrote:
> On Mon, Jul 05, 2021 at 03:47:09PM +0800, Rong Chen wrote:
>>
>> On 7/5/21 1:43 AM, Paul E. McKenney wrote:
>>> On Sun, Jul 04, 2021 at 05:42:36AM +0800, kernel test robot wrote:
>>>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>>>> head:   303392fd5c160822bf778270b28ec5ea50cab2b4
>>>> commit: 1253b9b87e42ab6a3d5c2cb27af2bdd67d7e50ff clocksource: Provide kernel module to test clocksource watchdog
>>>> date:   11 days ago
>>>> config: mips-randconfig-r015-20210702 (attached as .config)
>>>> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 9eb613b2de3163686b1a4bd1160f15ac56a4b083)
>>>> reproduce (this is a W=1 build):
>>>>           wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>>>>           chmod +x ~/bin/make.cross
>>>>           # install mips cross compiling tool for clang build
>>>>           # apt-get install binutils-mips-linux-gnu
>>>>           # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1253b9b87e42ab6a3d5c2cb27af2bdd67d7e50ff
>>>>           git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>>>>           git fetch --no-tags linus master
>>>>           git checkout 1253b9b87e42ab6a3d5c2cb27af2bdd67d7e50ff
>>>>           # save the attached .config to linux build tree
>>>>           COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips
>>>>
>>>> If you fix the issue, kindly add following tag as appropriate
>>>> Reported-by: kernel test robot <lkp@...el.com>
>>>>
>>>> All warnings (new ones prefixed by >>):
>>>>
>>>>>> kernel/time/clocksource-wdtest.c:47:22: warning: signed shift result (0x27BC86B00) requires 35 bits to represent, but 'long' only has 32 bits [-Wshift-overflow]
>>>>              .mult                   = TICK_NSEC << JIFFIES_SHIFT, /* details above */
>>>>                                        ~~~~~~~~~ ^  ~~~~~~~~~~~~~
>>>>      1 warning generated.
>>> You have CONFIG_HZ_24=y and this test module assumes HZ > 100, as noted
>>> just above the excerpt below:
>>>
>>> /* Assume HZ > 100. */
>>> #define JIFFIES_SHIFT   8
>>>
>>> So this is expected behavior.
>>>
>>> Would it help if I gave that comment some teeth, for example, as
>>> shown at the end of this email?
>> Hi Paul,
>>
>> I have confirmed that the below change can avoid the warning.
> Very good, and thank you!  May I add your Tested-by?

Yes, please.

Best Regards,
Rong Chen

>
> 							Thanx, Paul
>
>> Best Regards,
>> Rong Chen
>>
>>> ------------------------------------------------------------------------
>>>
>>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>>> index e1856030fa66..8f0ad6e4183c 100644
>>> --- a/lib/Kconfig.debug
>>> +++ b/lib/Kconfig.debug
>>> @@ -2573,6 +2573,7 @@ config TEST_FPU
>>>    config TEST_CLOCKSOURCE_WATCHDOG
>>>    	tristate "Test clocksource watchdog in kernel space"
>>>    	depends on CLOCKSOURCE_WATCHDOG
>>> +	depends on HZ >= 100
>>>    	help
>>>    	  Enable this option to create a kernel module that will trigger
>>>    	  a test of the clocksource watchdog.  This module may be loaded
>>> _______________________________________________
>>> kbuild-all mailing list -- kbuild-all@...ts.01.org
>>> To unsubscribe send an email to kbuild-all-leave@...ts.01.org