Re: [PATCH v2 bpf] bpf: Do not grab the bucket spinlock by default on htab batch ops

[kbuild test robot <lkp@intel.com>]

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Hi Brian,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on bpf/master]
[also build test WARNING on bpf-next/master v5.6-rc2 next-20200219]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Brian-Vazquez/bpf-Do-not-grab-the-bucket-spinlock-by-default-on-htab-batch-ops/20200220-073319
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git master
config: sh-randconfig-a001-20200219 (attached as .config)
compiler: sh4-linux-gcc (GCC) 7.5.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.5.0 make.cross ARCH=sh 

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

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/spinlock.h:54:0,
                    from include/linux/seqlock.h:36,
                    from include/linux/time.h:6,
                    from include/linux/ktime.h:24,
                    from include/linux/timer.h:6,
                    from include/linux/workqueue.h:9,
                    from include/linux/bpf.h:9,
                    from kernel//bpf/hashtab.c:5:
   kernel//bpf/hashtab.c: In function '__htab_map_lookup_and_delete_batch':
>> include/linux/irqflags.h:89:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
      arch_local_irq_restore(flags);  \
      ^~~~~~~~~~~~~~~~~~~~~~
   kernel//bpf/hashtab.c:1262:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~
--
   In file included from include/linux/spinlock.h:54:0,
                    from include/linux/seqlock.h:36,
                    from include/linux/time.h:6,
                    from include/linux/ktime.h:24,
                    from include/linux/timer.h:6,
                    from include/linux/workqueue.h:9,
                    from include/linux/bpf.h:9,
                    from kernel/bpf/hashtab.c:5:
   kernel/bpf/hashtab.c: In function '__htab_map_lookup_and_delete_batch':
>> include/linux/irqflags.h:89:3: warning: 'flags' may be used uninitialized in this function [-Wmaybe-uninitialized]
      arch_local_irq_restore(flags);  \
      ^~~~~~~~~~~~~~~~~~~~~~
   kernel/bpf/hashtab.c:1262:16: note: 'flags' was declared here
     unsigned long flags;
                   ^~~~~

vim +/flags +89 include/linux/irqflags.h

81d68a96a39844 Steven Rostedt 2008-05-12   75  
df9ee29270c11d David Howells  2010-10-07   76  /*
df9ee29270c11d David Howells  2010-10-07   77   * Wrap the arch provided IRQ routines to provide appropriate checks.
df9ee29270c11d David Howells  2010-10-07   78   */
df9ee29270c11d David Howells  2010-10-07   79  #define raw_local_irq_disable()		arch_local_irq_disable()
df9ee29270c11d David Howells  2010-10-07   80  #define raw_local_irq_enable()		arch_local_irq_enable()
df9ee29270c11d David Howells  2010-10-07   81  #define raw_local_irq_save(flags)			\
df9ee29270c11d David Howells  2010-10-07   82  	do {						\
df9ee29270c11d David Howells  2010-10-07   83  		typecheck(unsigned long, flags);	\
df9ee29270c11d David Howells  2010-10-07   84  		flags = arch_local_irq_save();		\
df9ee29270c11d David Howells  2010-10-07   85  	} while (0)
df9ee29270c11d David Howells  2010-10-07   86  #define raw_local_irq_restore(flags)			\
df9ee29270c11d David Howells  2010-10-07   87  	do {						\
df9ee29270c11d David Howells  2010-10-07   88  		typecheck(unsigned long, flags);	\
df9ee29270c11d David Howells  2010-10-07  @89  		arch_local_irq_restore(flags);		\
df9ee29270c11d David Howells  2010-10-07   90  	} while (0)
df9ee29270c11d David Howells  2010-10-07   91  #define raw_local_save_flags(flags)			\
df9ee29270c11d David Howells  2010-10-07   92  	do {						\
df9ee29270c11d David Howells  2010-10-07   93  		typecheck(unsigned long, flags);	\
df9ee29270c11d David Howells  2010-10-07   94  		flags = arch_local_save_flags();	\
df9ee29270c11d David Howells  2010-10-07   95  	} while (0)
df9ee29270c11d David Howells  2010-10-07   96  #define raw_irqs_disabled_flags(flags)			\
df9ee29270c11d David Howells  2010-10-07   97  	({						\
df9ee29270c11d David Howells  2010-10-07   98  		typecheck(unsigned long, flags);	\
df9ee29270c11d David Howells  2010-10-07   99  		arch_irqs_disabled_flags(flags);	\
df9ee29270c11d David Howells  2010-10-07  100  	})
df9ee29270c11d David Howells  2010-10-07  101  #define raw_irqs_disabled()		(arch_irqs_disabled())
df9ee29270c11d David Howells  2010-10-07  102  #define raw_safe_halt()			arch_safe_halt()
de30a2b355ea85 Ingo Molnar    2006-07-03  103  

:::::: The code at line 89 was first introduced by commit
:::::: df9ee29270c11dba7d0fe0b83ce47a4d8e8d2101 Fix IRQ flag handling naming

:::::: TO: David Howells <dhowells@redhat.com>
:::::: CC: David Howells <dhowells@redhat.com>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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