[rcu:test 70/72] arch/alpha/include/asm/pal.h:57:17: warning: 'flags' may be used uninitialized in this function

[kbuild test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git test
head:   77ef1b88654653681661fb0ce7cc1d6e712a409f
commit: 6ad9e6bcf543a758d4b7323cb2909ebd66f39ee4 [70/72] fixup! rcu/nocb: Avoid ->nocb_lock capture by corresponding CPU
config: alpha-allmodconfig (attached as .config)
compiler: alpha-linux-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 6ad9e6bcf543a758d4b7323cb2909ebd66f39ee4
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=alpha 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@xxxxxxxxx>

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 arch/alpha/include/asm/bug.h:8:0,
                    from include/linux/bug.h:5,
                    from include/linux/thread_info.h:12,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/alpha/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:78,
                    from include/linux/spinlock.h:51,
                    from kernel/rcu/tree.c:23:
   kernel/rcu/tree_plugin.h: In function 'do_nocb_deferred_wakeup_common':
>> arch/alpha/include/asm/pal.h:57:17: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
     register TYPE0 __r16 __asm__("$16") = arg0;  \
                    ^~~~~
   In file included from kernel/rcu/tree.c:3519:0:
   kernel/rcu/tree_plugin.h:1883:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~
   In file included from arch/alpha/include/asm/bug.h:8:0,
                    from include/linux/bug.h:5,
                    from include/linux/thread_info.h:12,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/alpha/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:78,
                    from include/linux/spinlock.h:51,
                    from kernel/rcu/tree.c:23:
   kernel/rcu/tree_plugin.h: In function 'rcu_nocb_gp_kthread':
>> arch/alpha/include/asm/pal.h:57:17: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
     register TYPE0 __r16 __asm__("$16") = arg0;  \
                    ^~~~~
   In file included from kernel/rcu/tree.c:3519:0:
   kernel/rcu/tree_plugin.h:1721:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~
--
   In file included from arch/alpha/include/asm/bug.h:8:0,
                    from include/linux/bug.h:5,
                    from include/linux/thread_info.h:12,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/alpha/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:78,
                    from include/linux/spinlock.h:51,
                    from kernel//rcu/tree.c:23:
   kernel//rcu/tree_plugin.h: In function 'do_nocb_deferred_wakeup_common':
>> arch/alpha/include/asm/pal.h:57:17: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
     register TYPE0 __r16 __asm__("$16") = arg0;  \
                    ^~~~~
   In file included from kernel//rcu/tree.c:3519:0:
   kernel//rcu/tree_plugin.h:1883:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~
   In file included from arch/alpha/include/asm/bug.h:8:0,
                    from include/linux/bug.h:5,
                    from include/linux/thread_info.h:12,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/alpha/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:78,
                    from include/linux/spinlock.h:51,
                    from kernel//rcu/tree.c:23:
   kernel//rcu/tree_plugin.h: In function 'rcu_nocb_gp_kthread':
>> arch/alpha/include/asm/pal.h:57:17: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
     register TYPE0 __r16 __asm__("$16") = arg0;  \
                    ^~~~~
   In file included from kernel//rcu/tree.c:3519:0:
   kernel//rcu/tree_plugin.h:1721:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~

vim +/flags +57 arch/alpha/include/asm/pal.h

ec221208 David Howells 2012-03-28  52  
ec221208 David Howells 2012-03-28  53  #define __CALL_PAL_RW1(NAME, RTYPE, TYPE0)			\
ec221208 David Howells 2012-03-28  54  extern inline RTYPE NAME(TYPE0 arg0)				\
ec221208 David Howells 2012-03-28  55  {								\
ec221208 David Howells 2012-03-28  56  	register RTYPE __r0 __asm__("$0");			\
ec221208 David Howells 2012-03-28 @57  	register TYPE0 __r16 __asm__("$16") = arg0;		\
ec221208 David Howells 2012-03-28  58  	__asm__ __volatile__(					\
ec221208 David Howells 2012-03-28  59  		"call_pal %2 # "#NAME				\
ec221208 David Howells 2012-03-28  60  		: "=r"(__r16), "=r"(__r0)			\
ec221208 David Howells 2012-03-28  61  		: "i"(PAL_ ## NAME), "0"(__r16)			\
ec221208 David Howells 2012-03-28  62  		: "$1", "$22", "$23", "$24", "$25");		\
ec221208 David Howells 2012-03-28  63  	return __r0;						\
ec221208 David Howells 2012-03-28  64  }
ec221208 David Howells 2012-03-28  65  

:::::: The code at line 57 was first introduced by commit
:::::: ec2212088c42ff7d1362629ec26dda4f3e8bdad3 Disintegrate asm/system.h for Alpha

:::::: TO: David Howells <dhowells@xxxxxxxxxx>
:::::: CC: David Howells <dhowells@xxxxxxxxxx>

---
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