Hi Waiman,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.10-rc1 next-20161224]
[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/Waiman-Long/futex-Introducing-throughput-optimized-TP-futexes/20161230-020021
config: i386-randconfig-x006-201652 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

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/futex.c: In function 'futex_lock':
>> kernel/futex.c:3776:13: warning: 'rspin_timeout' may be used uninitialized 
>> in this function [-Wmaybe-uninitialized]
        else if (curtime > rspin_timeout)
                ^
   kernel/futex.c:3656:6: note: 'rspin_timeout' was declared here
     u64 rspin_timeout;
         ^~~~~~~~~~~~~

vim +/rspin_timeout +3776 kernel/futex.c

  3760  
  3761                          if (!owner_task && (reader_value >= 0)) {
  3762                                  int old_count = reader_value;
  3763  
  3764                                  /*
  3765                                   * Reset timeout value if the old reader
  3766                                   * count is 0 or the reader value 
changes and
  3767                                   * handoff time hasn't been reached. 
Otherwise,
  3768                                   * disable reader spinning if the 
handoff time
  3769                                   * is reached.
  3770                                   */
  3771                                  reader_value = (uval & FUTEX_TID_MASK);
  3772                                  if (!old_count || (!handoff_set
  3773                                                 && (reader_value != 
old_count)))
  3774                                          rspin_timeout = curtime +
  3775                                                          
TP_RSPIN_TIMEOUT;
> 3776                                  else if (curtime > rspin_timeout)
  3777                                          reader_value = -1;
  3778                          }
  3779                          if (!handoff_set && (curtime > handoff_time)) {
  3780                                  WARN_ON(READ_ONCE(state->handoff_pid));
  3781                                  WRITE_ONCE(state->handoff_pid, vpid);
  3782  
  3783                                  /*
  3784                                   * Disable handoff check.

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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