In general it's preferable to avoid placing cpumasks on the stack, as
for large values of NR_CPUS these can consume significant amounts of
stack space and make stack overflows more likely.

- Both 2 arguments of cpumask_equal() is constant and free of change, no
  need to allocate extra cpumask variables.

- Merge cpumask_and(), cpumask_first() and cpumask_empty() into
  cpumask_first_and().

Signed-off-by: Dawei Li <dawei.li@shingroup.cn>
---
 arch/sparc/kernel/irq_64.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
index 5280e325d4d6..bc96f1bcd2fc 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -349,17 +349,13 @@ static unsigned int sun4u_compute_tid(unsigned long imap, unsigned long cpuid)
 #ifdef CONFIG_SMP
 static int irq_choose_cpu(unsigned int irq, const struct cpumask *affinity)
 {
-	cpumask_t mask;
 	int cpuid;
 
-	cpumask_copy(&mask, affinity);
-	if (cpumask_equal(&mask, cpu_online_mask)) {
+	if (cpumask_equal(affinity, cpu_online_mask)) {
 		cpuid = map_to_cpu(irq);
 	} else {
-		cpumask_t tmp;
-
-		cpumask_and(&tmp, cpu_online_mask, &mask);
-		cpuid = cpumask_empty(&tmp) ? map_to_cpu(irq) : cpumask_first(&tmp);
+		cpuid = cpumask_first_and(affinity, cpu_online_mask);
+		cpuid = cpuid < nr_cpu_ids ? : map_to_cpu(irq);
 	}
 
 	return cpuid;
-- 
2.27.0

Hi Dawei,

kernel test robot noticed the following build warnings:

[auto build test WARNING on v6.9-rc4]
[also build test WARNING on linus/master next-20240418]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dawei-Li/sparc-srmmu-Remove-on-stack-cpumask-var/20240418-185348
base:   v6.9-rc4
patch link:    https://lore.kernel.org/r/20240418104949.3606645-3-dawei.li%40shingroup.cn
patch subject: [PATCH 2/5] sparc/irq: Remove on-stack cpumask var
config: sparc64-defconfig (https://download.01.org/0day-ci/archive/20240419/202404190826.Zi1J5nCx-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240419/202404190826.Zi1J5nCx-lkp@intel.com/reproduce)

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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202404190826.Zi1J5nCx-lkp@intel.com/

All warnings (new ones prefixed by >>):

   arch/sparc/kernel/irq_64.c: In function 'irq_choose_cpu':
>> arch/sparc/kernel/irq_64.c:358:46: warning: the omitted middle operand in '?:' will always be 'true', suggest explicit middle operand [-Wparentheses]
     358 |                 cpuid = cpuid < nr_cpu_ids ? : map_to_cpu(irq);
         |                                              ^


vim +358 arch/sparc/kernel/irq_64.c

   348	
   349	#ifdef CONFIG_SMP
   350	static int irq_choose_cpu(unsigned int irq, const struct cpumask *affinity)
   351	{
   352		int cpuid;
   353	
   354		if (cpumask_equal(affinity, cpu_online_mask)) {
   355			cpuid = map_to_cpu(irq);
   356		} else {
   357			cpuid = cpumask_first_and(affinity, cpu_online_mask);
 > 358			cpuid = cpuid < nr_cpu_ids ? : map_to_cpu(irq);
   359		}
   360	
   361		return cpuid;
   362	}
   363	#else
   364	#define irq_choose_cpu(irq, affinity)	\
   365		real_hard_smp_processor_id()
   366	#endif
   367	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki