linux-kernel - kernel/futex/core.c:1748:2-8: WARNING: NULL check before some freeing functions is not needed.

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Message-ID: <202512222152.KF2aRkYU-lkp@intel.com>
Date: Mon, 22 Dec 2025 21:50:16 +0800
From: kernel test robot <lkp@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: kernel/futex/core.c:1748:2-8: WARNING: NULL check before
 some freeing functions is not needed.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   9448598b22c50c8a5bb77a9103e2d49f134c9578
commit: 56180dd20c19e5b0fa34822997a9ac66b517e7b3 futex: Use RCU-based per-CPU reference counting instead of rcuref_t
date:   5 months ago
config: arm-randconfig-r061-20251222 (https://download.01.org/0day-ci/archive/20251222/202512222152.KF2aRkYU-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 789845e319bbf346d42ee2c0090a9b8e153797a2)

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/202512222152.KF2aRkYU-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> kernel/futex/core.c:1748:2-8: WARNING: NULL check before some freeing functions is not needed.

vim +1748 kernel/futex/core.c

56180dd20c19e5 Peter Zijlstra            2025-07-10  1739  
80367ad01d93ac Sebastian Andrzej Siewior 2025-04-16  1740  void futex_hash_free(struct mm_struct *mm)
80367ad01d93ac Sebastian Andrzej Siewior 2025-04-16  1741  {
bd54df5ea7cada Sebastian Andrzej Siewior 2025-04-16  1742  	struct futex_private_hash *fph;
bd54df5ea7cada Sebastian Andrzej Siewior 2025-04-16  1743  
56180dd20c19e5 Peter Zijlstra            2025-07-10  1744  	free_percpu(mm->futex_ref);
bd54df5ea7cada Sebastian Andrzej Siewior 2025-04-16  1745  	kvfree(mm->futex_phash_new);
bd54df5ea7cada Sebastian Andrzej Siewior 2025-04-16  1746  	fph = rcu_dereference_raw(mm->futex_phash);
56180dd20c19e5 Peter Zijlstra            2025-07-10  1747  	if (fph)
bd54df5ea7cada Sebastian Andrzej Siewior 2025-04-16 @1748  		kvfree(fph);
bd54df5ea7cada Sebastian Andrzej Siewior 2025-04-16  1749  }
bd54df5ea7cada Sebastian Andrzej Siewior 2025-04-16  1750  

:::::: The code at line 1748 was first introduced by commit
:::::: bd54df5ea7cadac520e346d5f0fe5d58e635b6ba futex: Allow to resize the private local hash

:::::: TO: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
:::::: CC: Peter Zijlstra <peterz@...radead.org>

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