linux-kernel - Re: [paulmck-rcu:dev.2022.01.04a 52/55] kernel/stop_machine.c:207:6: warning: variable 't' set but not used

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Date:   Sat, 8 Jan 2022 07:49:48 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     kernel test robot <lkp@...el.com>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: [paulmck-rcu:dev.2022.01.04a 52/55] kernel/stop_machine.c:207:6:
 warning: variable 't' set but not used

On Sat, Jan 08, 2022 at 08:25:34PM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2022.01.04a
> head:   64595d0dff992756e8c6d53c0e9f1e3e50c451f7
> commit: 5cd99ef59351bcdd73ce5412934fda67d0ca2a1c [52/55] EXP timers: NMI stacktraces for last-resort jiffies update
> config: s390-randconfig-r026-20220107 (https://download.01.org/0day-ci/archive/20220108/202201082041.wv0NluSe-lkp@intel.com/config)
> compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 32167bfe64a4c5dd4eb3f7a58e24f4cba76f5ac2)
> 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 s390 cross compiling tool for clang build
>         # apt-get install binutils-s390x-linux-gnu
>         # https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=5cd99ef59351bcdd73ce5412934fda67d0ca2a1c
>         git remote add paulmck-rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
>         git fetch --no-tags paulmck-rcu dev.2022.01.04a
>         git checkout 5cd99ef59351bcdd73ce5412934fda67d0ca2a1c
>         # save the config file to linux build tree
>         mkdir build_dir
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>

This is a debug-only commit, since dropped.  But thank you for your
ongoing testing efforts!

							Thanx, Paul

> All warnings (new ones prefixed by >>):
> 
> >> kernel/stop_machine.c:207:6: warning: variable 't' set but not used [-Wunused-but-set-variable]
>            u64 t;
>                ^
>    1 warning generated.
> 
> 
> vim +/t +207 kernel/stop_machine.c
> 
>    201	
>    202	static void dump_multi_cpu_stop_state(struct multi_stop_data *msdata, bool *firsttime)
>    203	{
>    204		struct cpu_stopper *stopper;
>    205		unsigned long flags;
>    206		int cpu;
>  > 207		u64 t;
>    208	
>    209		tick_setup_sched_timer_dump();
>    210		pr_info("%s threads %d/%d state %d\n", __func__, atomic_read(&msdata->thread_ack), msdata->num_threads, msdata->state);
>    211		for_each_online_cpu(cpu) {
>    212			if (cpu_is_offline(cpu))
>    213				continue;
>    214			stopper = &per_cpu(cpu_stopper, cpu);
>    215			raw_spin_lock_irqsave(&stopper->lock, flags);
>    216			t = ktime_get();
>    217	//		tlast = stopper->lasttime;
>    218			pr_info("%s: %s%s ->state=%#x%s\n", __func__, stopper->thread->comm, stopper->thread == current ? " (me)" : "", stopper->thread->__state, task_curr(stopper->thread) ? "" : " Not running!");
>    219			raw_spin_unlock_irqrestore(&stopper->lock, flags);
>    220			if (firsttime && *firsttime && !task_curr(stopper->thread)) {
>    221				trigger_single_cpu_backtrace(cpu);
>    222				*firsttime = false;
>    223			}
>    224	//		if (time_after64(t, tlast + NSEC_PER_SEC) &&
>    225	//		    smp_load_acquire(&multi_stop_cpu_ipi_handled)) {
>    226	//			pr_info("%s: sending IPI from CPU %d to CPU %d\n", __func__, raw_smp_processor_id(), cpu);
>    227	//			WRITE_ONCE(multi_stop_cpu_ipi_handled, false);
>    228	//			smp_mb();
>    229	//			smp_call_function_single(cpu, multi_stop_cpu_ipi, NULL, 0);
>    230	//		}
>    231		}
>    232	}
>    233	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org