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Message-ID: <1471378762.29515.4.camel@j-VirtualBox>
Subject: Re: [PATCH v2] locking/mutex: Prevent lock starvation when spinning
 is enabled
From: Jason Low <jason.low2@hpe.com>
To: kbuild test robot <lkp@intel.com>
Cc: jason.low2@hpe.com, kbuild-all@01.org,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        imre.deak@intel.com, linux-kernel@vger.kernel.org,
        Waiman Long <Waiman.Long@hpe.com>, Davidlohr Bueso <dave@stgolabs.net>,
        Tim Chen <tim.c.chen@linux.intel.com>, terry.rudd@hpe.com,
        "Paul E. McKenney" <paulmck@us.ibm.com>, jason.low2@hp.com
Date: Tue, 16 Aug 2016 13:19:22 -0700
In-Reply-To: <201608110348.S1i8J408%fengguang.wu@intel.com>
References: <201608110348.S1i8J408%fengguang.wu@intel.com>
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On Thu, 2016-08-11 at 04:01 +0800, kbuild test robot wrote:
> Hi Jason,
> 
> [auto build test ERROR on tip/locking/core]
> [also build test ERROR on v4.8-rc1 next-20160809]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Jason-Low/locking-mutex-Prevent-lock-starvation-when-spinning-is-enabled/20160811-034327
> config: x86_64-randconfig-x013-201632 (attached as .config)
> compiler: gcc-6 (Debian 6.1.1-9) 6.1.1 20160705
> reproduce:
>         # save the attached .config to linux build tree
>         make ARCH=x86_64 
> 
> All error/warnings (new ones prefixed by >>):
> 
>    kernel/locking/mutex.c: In function 'do_yield_to_waiter':
> >> kernel/locking/mutex.c:441:10: error: 'struct mutex' has no member named 'yield_to_waiter'
>      if (lock->yield_to_waiter != true)
>              ^~
>    kernel/locking/mutex.c:442:7: error: 'struct mutex' has no member named 'yield_to_waiter'
>       lock->yield_to_waiter = true;
>           ^~
>    kernel/locking/mutex.c: In function 'clear_yield_to_waiter':
>    kernel/locking/mutex.c:447:6: error: 'struct mutex' has no member named 'yield_to_waiter'
>      lock->yield_to_waiter = false;
>          ^~
>    kernel/locking/mutex.c: In function 'need_yield_to_waiter':
>    kernel/locking/mutex.c:452:13: error: 'struct mutex' has no member named 'yield_to_waiter'
>      return lock->yield_to_waiter;
>                 ^~

These compilation errors occur in the !SMP case where the
yield_to_waiter variable does not get defined in the mutex structure,
but the waiter yield functions still make use of the variable.

They should be addressed by also checking for #if defined(CONFIG_SMP)
when defining those functions as Waiman had suggested.

Thanks,
Jason