Re: [rcu:dev.2020.06.02a 85/90] kernel/smp.c:122: undefined reference to `__udivdi3'

[Paul E. McKenney]

On Sat, Jun 06, 2020 at 05:38:31AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2020.06.02a
> head:   5216948905dd07a84cef8a7dc72c2ec076802efd
> commit: 92ebbb71443dced2019cd24b737ce60b03a29e10 [85/90] EXP kernel/smp: Provide CSD lock timeout diagnostics
> config: i386-randconfig-c001-20200605 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-13) 9.3.0
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> 
> All errors (new ones prefixed by >>, old ones prefixed by <<):
> 
> ld: kernel/smp.o: in function `csd_lock_wait':
> >> kernel/smp.c:122: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:128: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:136: undefined reference to `__umoddi3'
> ld: kernel/smp.c:136: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:122: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:128: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:136: undefined reference to `__umoddi3'
> ld: kernel/smp.c:136: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:122: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:128: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:136: undefined reference to `__umoddi3'
> ld: kernel/smp.c:136: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:122: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:128: undefined reference to `__udivdi3'
> >> ld: kernel/smp.c:136: undefined reference to `__umoddi3'
> ld: kernel/smp.c:136: undefined reference to `__udivdi3'

Good catch, thank you, fixup patch applied.

							Thanx, Paul

> vim +122 kernel/smp.c
> 
>    107	
>    108	/*
>    109	 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
>    110	 *
>    111	 * For non-synchronous ipi calls the csd can still be in use by the
>    112	 * previous function call. For multi-cpu calls its even more interesting
>    113	 * as we'll have to ensure no other cpu is observing our csd.
>    114	 */
>    115	static __always_inline void csd_lock_wait(call_single_data_t *csd)
>    116	{
>    117		int bug_id = 0;
>    118		int cpu;
>    119		call_single_data_t *cpu_cur_csd;
>    120		u64 ts0, ts1, ts2, ts_delta;
>    121	
>  > 122		ts1 = ts0 = sched_clock() / 1000 / 1000;
>    123		for (;;) {
>    124			unsigned long flags = READ_ONCE(csd->flags);
>    125	
>    126			if (!(flags & CSD_FLAG_LOCK))
>    127				break;
>  > 128			ts2 = sched_clock() / 1000 / 1000;
>    129			ts_delta = ts2 - ts1;
>    130			if (unlikely(ts_delta > CSD_LOCK_TIMEOUT)) {
>    131				bug_id = atomic_inc_return(&csd_bug_count);
>    132				cpu = csd->cpu;
>    133				smp_mb(); // No stale cur_csd values!
>    134				cpu_cur_csd = per_cpu(cur_csd, cpu);
>    135				smp_mb(); // No refetching cur_csd values!
>  > 136				printk("csd: Detected non-responsive CSD lock (#%d) on CPU#%d, waiting %Ld.%03Ld secs for CPU#%02d %pf(%ps), currently %s.\n",
>    137				       bug_id, raw_smp_processor_id(),
>    138				       ts_delta/1000ULL, ts_delta % 1000ULL, cpu,
>    139				       csd->func, csd->info,
>    140				       !cpu_cur_csd ? "unresponsive"
>    141						: csd == cpu_cur_csd
>    142							? "handling this request"
>    143							: "handling prior request");
>    144				if (!trigger_single_cpu_backtrace(cpu))
>    145					dump_cpu_task(cpu);
>    146				if (!cpu_cur_csd) {
>    147					printk("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", bug_id, raw_smp_processor_id(), cpu);
>    148					arch_send_call_function_single_ipi(cpu);
>    149				}
>    150				dump_stack();
>    151				ts1 = ts2;
>    152			}
>    153			cpu_relax();
>    154		}
>    155		smp_acquire__after_ctrl_dep();
>    156		if (unlikely(bug_id))
>    157			printk("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock after all. Phew!\n", bug_id, raw_smp_processor_id(), cpu);
>    158	}
>    159	
> 
> ---
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