linux-kernel - Re: [PATCH v3 14/17] timer: Implement the hierarchical pull model

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Date:   Wed, 26 Oct 2022 00:36:07 +0800
From:   kernel test robot <lkp@...el.com>
To:     Anna-Maria Behnsen <anna-maria@...utronix.de>,
        linux-kernel@...r.kernel.org
Cc:     oe-kbuild-all@...ts.linux.dev,
        John Stultz <john.stultz@...aro.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pm@...r.kernel.org, Arjan van de Ven <arjan@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: Re: [PATCH v3 14/17] timer: Implement the hierarchical pull model

Hi Anna-Maria,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on tip/timers/core]
[also build test WARNING on powerpc/next tip/x86/core linus/master v6.1-rc2]
[cannot apply to tip/timers/nohz next-20221025]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Anna-Maria-Behnsen/timer-Move-from-a-push-remote-at-enqueue-to-a-pull-at-expiry-model/20221025-220106
patch link:    https://lore.kernel.org/r/20221025135850.51044-15-anna-maria%40linutronix.de
patch subject: [PATCH v3 14/17] timer: Implement the hierarchical pull model
config: loongarch-allyesconfig (attached as .config)
compiler: loongarch64-linux-gcc (GCC) 12.1.0
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
        # https://github.com/intel-lab-lkp/linux/commit/b57766ae36b5e3dd11225f0259f9fd7d39a79e94
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Anna-Maria-Behnsen/timer-Move-from-a-push-remote-at-enqueue-to-a-pull-at-expiry-model/20221025-220106
        git checkout b57766ae36b5e3dd11225f0259f9fd7d39a79e94
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=loongarch SHELL=/bin/bash kernel/time/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

   kernel/time/timer_migration.c: In function 'tmigr_cpu_deactivate':
>> kernel/time/timer_migration.c:633:21: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
     633 |                 u64 ret = tmc->wakeup;
         |                     ^~~


vim +/ret +633 kernel/time/timer_migration.c

   602	
   603	/**
   604	 * tmigr_cpu_deactivate - Put current CPU into inactive state
   605	 * @nextexp:	The next timer event expiry set in the current CPU
   606	 *
   607	 * Must be called with interrupts disabled.
   608	 *
   609	 * Return: next event of the current CPU or next event from the hierarchy
   610	 * if this CPU is the top level migrator or hierarchy is completely idle.
   611	 */
   612	u64 tmigr_cpu_deactivate(u64 nextexp)
   613	{
   614		struct tmigr_cpu *tmc = this_cpu_ptr(&tmigr_cpu);
   615		u64 ret = KTIME_MAX;
   616	
   617		if (!is_tmigr_enabled() || !tmc->tmgroup || !tmc->online)
   618			return ret;
   619	
   620		raw_spin_lock(&tmc->lock);
   621	
   622		/*
   623		 * CPU is already deactivated in timer migration
   624		 * hierarchy. tick_nohz_get_sleep_length() calls
   625		 * tick_nohz_next_event() and thereby timer idle path is
   626		 * executed once more. tmc->wakeup holds the first timer, when
   627		 * timer migration hierarchy is completely idle and remote
   628		 * expiry was done. If there is no new next expiry value
   629		 * handed in which should be inserted into the timer migration
   630		 * hierarchy, wakeup value is returned.
   631		 */
   632		if (tmc->idle) {
 > 633			u64 ret = tmc->wakeup;
   634	
   635			tmc->wakeup = KTIME_MAX;
   636	
   637			if (nextexp != KTIME_MAX) {
   638				if (nextexp != tmc->cpuevt.nextevt.expires ||
   639				    test_bit(0, &tmc->cpuevt.ignore))
   640					ret = tmigr_new_timer(tmc, nextexp);
   641			}
   642	
   643			goto unlock;
   644		}
   645	
   646		/*
   647		 * When tmigr_remote is active, set cpu inactive path and queuing of
   648		 * nextexp is done by handle remote path.
   649		 */
   650		ret = __tmigr_cpu_deactivate(tmc, nextexp);
   651	
   652		tmc->idle = 1;
   653	
   654	unlock:
   655		raw_spin_unlock(&tmc->lock);
   656		return ret;
   657	}
   658	

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

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