Re: [PATCH v2 1/2] livepatch: introduce shadow variable API

[kbuild test robot]

Hi Joe,

[auto build test WARNING on jikos-livepatching/for-next]
[also build test WARNING on v4.12-rc7 next-20170630]
[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/Joe-Lawrence/livepatch-introduce-shadow-variable-API/20170630-061942
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching.git for-next
config: s390-performance_defconfig (attached as .config)
compiler: s390x-linux-gnu-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        wget https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=s390 

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 >>):

   In file included from include/linux/irqflags.h:15:0,
                    from arch/s390/include/asm/processor.h:35,
                    from arch/s390/include/asm/thread_info.h:24,
                    from include/linux/thread_info.h:37,
                    from arch/s390/include/asm/preempt.h:5,
                    from include/linux/preempt.h:80,
                    from include/linux/spinlock.h:50,
                    from include/linux/rcupdate.h:38,
                    from include/linux/rculist.h:10,
                    from include/linux/hashtable.h:13,
                    from kernel/livepatch/shadow.c:49:
   kernel/livepatch/shadow.c: In function '_klp_shadow_attach':
>> arch/s390/include/asm/irqflags.h:63:12: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if (flags & ARCH_IRQ_ENABLED)
               ^
   kernel/livepatch/shadow.c:135:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~
--
   In file included from include/linux/irqflags.h:15:0,
                    from arch/s390/include/asm/processor.h:35,
                    from arch/s390/include/asm/thread_info.h:24,
                    from include/linux/thread_info.h:37,
                    from arch/s390/include/asm/preempt.h:5,
                    from include/linux/preempt.h:80,
                    from include/linux/spinlock.h:50,
                    from include/linux/rcupdate.h:38,
                    from include/linux/rculist.h:10,
                    from include/linux/hashtable.h:13,
                    from kernel//livepatch/shadow.c:49:
   kernel//livepatch/shadow.c: In function '_klp_shadow_attach':
>> arch/s390/include/asm/irqflags.h:63:12: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
     if (flags & ARCH_IRQ_ENABLED)
               ^
   kernel//livepatch/shadow.c:135:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~

vim +/flags +63 arch/s390/include/asm/irqflags.h

94c12cc7d include/asm-s390/irqflags.h      Martin Schwidefsky    2006-09-28  47  }
94c12cc7d include/asm-s390/irqflags.h      Martin Schwidefsky    2006-09-28  48  
f433c4aec arch/s390/include/asm/irqflags.h Steven Rostedt        2011-07-24  49  static inline notrace void arch_local_irq_disable(void)
df9ee2927 arch/s390/include/asm/irqflags.h David Howells         2010-10-07  50  {
df9ee2927 arch/s390/include/asm/irqflags.h David Howells         2010-10-07  51  	arch_local_irq_save();
df9ee2927 arch/s390/include/asm/irqflags.h David Howells         2010-10-07  52  }
1f194a4c3 include/asm-s390/irqflags.h      Heiko Carstens        2006-07-03  53  
f433c4aec arch/s390/include/asm/irqflags.h Steven Rostedt        2011-07-24  54  static inline notrace void arch_local_irq_enable(void)
94c12cc7d include/asm-s390/irqflags.h      Martin Schwidefsky    2006-09-28  55  {
df9ee2927 arch/s390/include/asm/irqflags.h David Howells         2010-10-07  56  	__arch_local_irq_stosm(0x03);
94c12cc7d include/asm-s390/irqflags.h      Martin Schwidefsky    2006-09-28  57  }
1f194a4c3 include/asm-s390/irqflags.h      Heiko Carstens        2006-07-03  58  
204ee2c56 arch/s390/include/asm/irqflags.h Christian Borntraeger 2016-01-11  59  /* This only restores external and I/O interrupt state */
f433c4aec arch/s390/include/asm/irqflags.h Steven Rostedt        2011-07-24  60  static inline notrace void arch_local_irq_restore(unsigned long flags)
df9ee2927 arch/s390/include/asm/irqflags.h David Howells         2010-10-07  61  {
204ee2c56 arch/s390/include/asm/irqflags.h Christian Borntraeger 2016-01-11  62  	/* only disabled->disabled and disabled->enabled is valid */
204ee2c56 arch/s390/include/asm/irqflags.h Christian Borntraeger 2016-01-11 @63  	if (flags & ARCH_IRQ_ENABLED)
204ee2c56 arch/s390/include/asm/irqflags.h Christian Borntraeger 2016-01-11  64  		arch_local_irq_enable();
df9ee2927 arch/s390/include/asm/irqflags.h David Howells         2010-10-07  65  }
df9ee2927 arch/s390/include/asm/irqflags.h David Howells         2010-10-07  66  
f433c4aec arch/s390/include/asm/irqflags.h Steven Rostedt        2011-07-24  67  static inline notrace bool arch_irqs_disabled_flags(unsigned long flags)
1f194a4c3 include/asm-s390/irqflags.h      Heiko Carstens        2006-07-03  68  {
204ee2c56 arch/s390/include/asm/irqflags.h Christian Borntraeger 2016-01-11  69  	return !(flags & ARCH_IRQ_ENABLED);
1f194a4c3 include/asm-s390/irqflags.h      Heiko Carstens        2006-07-03  70  }
1f194a4c3 include/asm-s390/irqflags.h      Heiko Carstens        2006-07-03  71  

:::::: The code at line 63 was first introduced by commit
:::::: 204ee2c5643199a25181ec04ea645d00709c2a5a s390/irqflags: optimize irq restore

:::::: TO: Christian Borntraeger <borntraeger@xxxxxxxxxx>
:::::: CC: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

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