linux-kernel - kernel/sched/isolation.c:143 housekeeping_setup() warn: always true condition '(first

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Date: Tue, 30 Apr 2024 09:41:32 +0800
From: kernel test robot <lkp@...el.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, Phil Auld <pauld@...hat.com>
Subject: kernel/sched/isolation.c:143 housekeeping_setup() warn: always true
 condition '(first_cpu >= 0) => (0-u32max >= 0)'

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   98369dccd2f8e16bf4c6621053af7aa4821dcf8e
commit: 257bf89d84121280904800acd25cc2c444c717ae sched/isolation: Fix boot crash when maxcpus < first housekeeping CPU
date:   2 days ago
config: xtensa-randconfig-r081-20240429 (https://download.01.org/0day-ci/archive/20240430/202404300915.WNvfwBz3-lkp@intel.com/config)
compiler: xtensa-linux-gcc (GCC) 13.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202404300915.WNvfwBz3-lkp@intel.com/

New smatch warnings:
kernel/sched/isolation.c:143 housekeeping_setup() warn: always true condition '(first_cpu >= 0) => (0-u32max >= 0)'

Old smatch warnings:
arch/xtensa/include/asm/thread_info.h:97 current_thread_info() warn: inconsistent indenting

vim +143 kernel/sched/isolation.c

   117	
   118	static int __init housekeeping_setup(char *str, unsigned long flags)
   119	{
   120		cpumask_var_t non_housekeeping_mask, housekeeping_staging;
   121		unsigned int first_cpu;
   122		int err = 0;
   123	
   124		if ((flags & HK_FLAG_TICK) && !(housekeeping.flags & HK_FLAG_TICK)) {
   125			if (!IS_ENABLED(CONFIG_NO_HZ_FULL)) {
   126				pr_warn("Housekeeping: nohz unsupported."
   127					" Build with CONFIG_NO_HZ_FULL\n");
   128				return 0;
   129			}
   130		}
   131	
   132		alloc_bootmem_cpumask_var(&non_housekeeping_mask);
   133		if (cpulist_parse(str, non_housekeeping_mask) < 0) {
   134			pr_warn("Housekeeping: nohz_full= or isolcpus= incorrect CPU range\n");
   135			goto free_non_housekeeping_mask;
   136		}
   137	
   138		alloc_bootmem_cpumask_var(&housekeeping_staging);
   139		cpumask_andnot(housekeeping_staging,
   140			       cpu_possible_mask, non_housekeeping_mask);
   141	
   142		first_cpu = cpumask_first_and(cpu_present_mask, housekeeping_staging);
 > 143		if (first_cpu >= nr_cpu_ids || first_cpu >= setup_max_cpus) {
   144			__cpumask_set_cpu(smp_processor_id(), housekeeping_staging);
   145			__cpumask_clear_cpu(smp_processor_id(), non_housekeeping_mask);
   146			if (!housekeeping.flags) {
   147				pr_warn("Housekeeping: must include one present CPU, "
   148					"using boot CPU:%d\n", smp_processor_id());
   149			}
   150		}
   151	
   152		if (cpumask_empty(non_housekeeping_mask))
   153			goto free_housekeeping_staging;
   154	
   155		if (!housekeeping.flags) {
   156			/* First setup call ("nohz_full=" or "isolcpus=") */
   157			enum hk_type type;
   158	
   159			for_each_set_bit(type, &flags, HK_TYPE_MAX)
   160				housekeeping_setup_type(type, housekeeping_staging);
   161		} else {
   162			/* Second setup call ("nohz_full=" after "isolcpus=" or the reverse) */
   163			enum hk_type type;
   164			unsigned long iter_flags = flags & housekeeping.flags;
   165	
   166			for_each_set_bit(type, &iter_flags, HK_TYPE_MAX) {
   167				if (!cpumask_equal(housekeeping_staging,
   168						   housekeeping.cpumasks[type])) {
   169					pr_warn("Housekeeping: nohz_full= must match isolcpus=\n");
   170					goto free_housekeeping_staging;
   171				}
   172			}
   173	
   174			iter_flags = flags & ~housekeeping.flags;
   175	
   176			for_each_set_bit(type, &iter_flags, HK_TYPE_MAX)
   177				housekeeping_setup_type(type, housekeeping_staging);
   178		}
   179	
   180		if ((flags & HK_FLAG_TICK) && !(housekeeping.flags & HK_FLAG_TICK))
   181			tick_nohz_full_setup(non_housekeeping_mask);
   182	
   183		housekeeping.flags |= flags;
   184		err = 1;
   185	
   186	free_housekeeping_staging:
   187		free_bootmem_cpumask_var(housekeeping_staging);
   188	free_non_housekeeping_mask:
   189		free_bootmem_cpumask_var(non_housekeeping_mask);
   190	
   191		return err;
   192	}
   193	

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