[kbuild-all] [ti:ti-rt-linux-5.4.y 10/10] kernel/rcu/srcutree.c:739:30: warning: unused variable 'sp_llock'

tree: git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git ti-rt-linux-5.4.y head: 39a31e930c9ef3b4f39306c49cbaa9c58c94e353 commit: 39a31e930c9ef3b4f39306c49cbaa9c58c94e353 [10/10] Merged TI feature ti_linux_base_rt into ti-rt-linux-5.4.y config: arm64-randconfig-r034-20210318 (attached as .config) compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 6db3ab2903f42712f44000afb5aa467efbd25f35) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install arm64 cross compiling tool for clang build # apt-get install binutils-aarch64-linux-gnu git remote add ti git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git git fetch --no-tags ti ti-rt-linux-5.4.y git checkout 39a31e930c9ef3b4f39306c49cbaa9c58c94e353 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): static DEFINE_LOCAL_IRQ_LOCK(sp_llock); ^ 1 warning generated. vim +/sp_llock +739 kernel/rcu/srcutree.c dad81a2026841b Paul E. McKenney 2017-03-25 738 8a5f2a03d28c15 Sebastian Andrzej Siewior 2017-10-12 @739 static DEFINE_LOCAL_IRQ_LOCK(sp_llock); 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 740 /* 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 741 * If SRCU is likely idle, return true, otherwise return false. 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 742 * 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 743 * Note that it is OK for several current from-idle requests for a new 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 744 * grace period from idle to specify expediting because they will all end 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 745 * up requesting the same grace period anyhow. So no loss. 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 746 * 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 747 * Note also that if any CPU (including the current one) is still invoking 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 748 * callbacks, this function will nevertheless say "idle". This is not 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 749 * ideal, but the overhead of checking all CPUs' callback lists is even 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 750 * less ideal, especially on large systems. Furthermore, the wakeup 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 751 * can happen before the callback is fully removed, so we have no choice 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 752 * but to accept this type of error. 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 753 * 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 754 * This function is also subject to counter-wrap errors, but let's face 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 755 * it, if this function was preempted for enough time for the counters 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 756 * to wrap, it really doesn't matter whether or not we expedite the grace 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 757 * period. The extra overhead of a needlessly expedited grace period is 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 758 * negligible when amoritized over that time period, and the extra latency 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 759 * of a needlessly non-expedited grace period is similarly negligible. 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 760 */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 761 static bool srcu_might_be_idle(struct srcu_struct *ssp) 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 762 { 22607d66bbc3e8 Paul E. McKenney 2017-04-25 763 unsigned long curseq; 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 764 unsigned long flags; 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 765 struct srcu_data *sdp; 22607d66bbc3e8 Paul E. McKenney 2017-04-25 766 unsigned long t; c71706a5ffff80 Paul E. McKenney 2019-11-04 767 unsigned long tlast; 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 768 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 769 /* If the local srcu_data structure has callbacks, not idle. */ 8a5f2a03d28c15 Sebastian Andrzej Siewior 2017-10-12 770 local_lock_irqsave(sp_llock, flags); aacb5d91ab1bfb Paul E. McKenney 2018-10-28 771 sdp = this_cpu_ptr(ssp->sda); 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 772 if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) { 8a5f2a03d28c15 Sebastian Andrzej Siewior 2017-10-12 773 local_unlock_irqrestore(sp_llock, flags); 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 774 return false; /* Callbacks already present, so not idle. */ 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 775 } 8a5f2a03d28c15 Sebastian Andrzej Siewior 2017-10-12 776 local_unlock_irqrestore(sp_llock, flags); 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 777 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 778 /* 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 779 * No local callbacks, so probabalistically probe global state. 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 780 * Exact information would require acquiring locks, which would 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 781 * kill scalability, hence the probabalistic nature of the probe. 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 782 */ 22607d66bbc3e8 Paul E. McKenney 2017-04-25 783 22607d66bbc3e8 Paul E. McKenney 2017-04-25 784 /* First, see if enough time has passed since the last GP. */ 22607d66bbc3e8 Paul E. McKenney 2017-04-25 785 t = ktime_get_mono_fast_ns(); c71706a5ffff80 Paul E. McKenney 2019-11-04 786 tlast = READ_ONCE(ssp->srcu_last_gp_end); 22607d66bbc3e8 Paul E. McKenney 2017-04-25 787 if (exp_holdoff == 0 || c71706a5ffff80 Paul E. McKenney 2019-11-04 788 time_in_range_open(t, tlast, tlast + exp_holdoff)) 22607d66bbc3e8 Paul E. McKenney 2017-04-25 789 return false; /* Too soon after last GP. */ 22607d66bbc3e8 Paul E. McKenney 2017-04-25 790 22607d66bbc3e8 Paul E. McKenney 2017-04-25 791 /* Next, check for probable idleness. */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 792 curseq = rcu_seq_current(&ssp->srcu_gp_seq); 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 793 smp_mb(); /* Order ->srcu_gp_seq with ->srcu_gp_seq_needed. */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 794 if (ULONG_CMP_LT(curseq, READ_ONCE(ssp->srcu_gp_seq_needed))) 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 795 return false; /* Grace period in progress, so not idle. */ 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 796 smp_mb(); /* Order ->srcu_gp_seq with prior access. */ aacb5d91ab1bfb Paul E. McKenney 2018-10-28 797 if (curseq != rcu_seq_current(&ssp->srcu_gp_seq)) 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 798 return false; /* GP # changed, so not idle. */ 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 799 return true; /* With reasonable probability, idle! */ 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 800 } 2da4b2a7fd8de5 Paul E. McKenney 2017-04-25 801 :::::: The code at line 739 was first introduced by commit :::::: 8a5f2a03d28c1523e49a5c501b74ccc567d321f7 srcu: replace local_irqsave() with a locallock :::::: TO: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de&gt; :::::: CC: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org