linux-kernel - [tip:timers/urgent 2/4] kernel/time/tick-common.c:233:3: warning: 'next_event' may be used uninitialized in this function

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Date:   Sun, 25 Dec 2016 22:04:16 +0800
From:   kbuild test robot <fengguang.wu@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org, tipbuild@...or.com
Subject: [tip:timers/urgent 2/4] kernel/time/tick-common.c:233:3: warning:
 'next_event' may be used uninitialized in this function

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/urgent
head:   75f62a4c59d4fce751f8ee71f87955943fd69b74
commit: 64dac5c9e0f5a933e4520f0cb689b7b143925207 [2/4] ktime: Get rid of the union
config: blackfin-BF561-EZKIT-SMP_defconfig (attached as .config)
compiler: bfin-uclinux-gcc (GCC) 6.2.0
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 64dac5c9e0f5a933e4520f0cb689b7b143925207
        # save the attached .config to linux build tree
        make.cross ARCH=blackfin 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   kernel/time/tick-common.c: In function 'tick_setup_device':
>> kernel/time/tick-common.c:233:3: warning: 'next_event' may be used uninitialized in this function [-Wmaybe-uninitialized]
      tick_setup_oneshot(newdev, handler, next_event);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

vim +/next_event +233 kernel/time/tick-common.c

320ab2b0b Rusty Russell     2008-12-13  217  	if (!cpumask_equal(newdev->cpumask, cpumask))
0de26520c Rusty Russell     2008-12-13  218  		irq_set_affinity(newdev->irq, cpumask);
906568c9c Thomas Gleixner   2007-02-16  219  
f8381cba0 Thomas Gleixner   2007-02-16  220  	/*
f8381cba0 Thomas Gleixner   2007-02-16  221  	 * When global broadcasting is active, check if the current
f8381cba0 Thomas Gleixner   2007-02-16  222  	 * device is registered as a placeholder for broadcast mode.
f8381cba0 Thomas Gleixner   2007-02-16  223  	 * This allows us to handle this x86 misfeature in a generic
07bd11729 Thomas Gleixner   2013-07-01  224  	 * way. This function also returns !=0 when we keep the
07bd11729 Thomas Gleixner   2013-07-01  225  	 * current active broadcast state for this CPU.
f8381cba0 Thomas Gleixner   2007-02-16  226  	 */
f8381cba0 Thomas Gleixner   2007-02-16  227  	if (tick_device_uses_broadcast(newdev, cpu))
f8381cba0 Thomas Gleixner   2007-02-16  228  		return;
f8381cba0 Thomas Gleixner   2007-02-16  229  
906568c9c Thomas Gleixner   2007-02-16  230  	if (td->mode == TICKDEV_MODE_PERIODIC)
906568c9c Thomas Gleixner   2007-02-16  231  		tick_setup_periodic(newdev, 0);
79bf2bb33 Thomas Gleixner   2007-02-16  232  	else
79bf2bb33 Thomas Gleixner   2007-02-16 @233  		tick_setup_oneshot(newdev, handler, next_event);
906568c9c Thomas Gleixner   2007-02-16  234  }
906568c9c Thomas Gleixner   2007-02-16  235  
03e13cf5e Thomas Gleixner   2013-04-25  236  void tick_install_replacement(struct clock_event_device *newdev)
03e13cf5e Thomas Gleixner   2013-04-25  237  {
22127e93c Christoph Lameter 2014-08-17  238  	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
03e13cf5e Thomas Gleixner   2013-04-25  239  	int cpu = smp_processor_id();
03e13cf5e Thomas Gleixner   2013-04-25  240  
03e13cf5e Thomas Gleixner   2013-04-25  241  	clockevents_exchange_device(td->evtdev, newdev);

:::::: The code at line 233 was first introduced by commit
:::::: 79bf2bb335b85db25d27421c798595a2fa2a0e82 [PATCH] tick-management: dyntick / highres functionality

:::::: TO: Thomas Gleixner <tglx@...utronix.de>
:::::: CC: Linus Torvalds <torvalds@...dy.linux-foundation.org>

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