Re: [PATCH 1/2] kvfree_rcu: Release a page cache under memory pressure

[kernel test robot <lkp@intel.com>]

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Hi "Uladzislau,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on rcu/dev]
[also build test WARNING on linux/master linus/master v5.12-rc2 next-20210305]
[cannot apply to hnaz-linux-mm/master]
[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]

url:    https://github.com/0day-ci/linux/commits/Uladzislau-Rezki-Sony/kvfree_rcu-Release-a-page-cache-under-memory-pressure/20210309-035155
base:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev
config: riscv-randconfig-r002-20210309 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 3a11a41795bec548e91621caaa4cc00fc31b2212)
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 riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://github.com/0day-ci/linux/commit/d1c3a54d06b2b088b2a7b4e7f2a0a85bcbfbf53a
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Uladzislau-Rezki-Sony/kvfree_rcu-Release-a-page-cache-under-memory-pressure/20210309-035155
        git checkout d1c3a54d06b2b088b2a7b4e7f2a0a85bcbfbf53a
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> kernel/rcu/tree.c:3518:7: warning: variable '__ret' is uninitialized when used here [-Wuninitialized]
                   if (xchg(&backoff_page_cache_fill, false)) {
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/cmpxchg.h:146:23: note: expanded from macro 'xchg'
           (__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr)));        \
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/cmpxchg.h:140:2: note: expanded from macro '__xchg'
           __ret;                                                          \
           ^~~~~
   kernel/rcu/tree.c:3518:7: note: variable '__ret' is declared here
   arch/riscv/include/asm/cmpxchg.h:146:23: note: expanded from macro 'xchg'
           (__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr)));        \
                                ^
   arch/riscv/include/asm/cmpxchg.h:121:2: note: expanded from macro '__xchg'
           __typeof__(*(ptr)) __ret;                                       \
           ^
   1 warning generated.


vim +/__ret +3518 kernel/rcu/tree.c

  3512	
  3513	static void
  3514	run_page_cache_worker(struct kfree_rcu_cpu *krcp)
  3515	{
  3516		if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
  3517				!atomic_xchg(&krcp->work_in_progress, 1)) {
> 3518			if (xchg(&backoff_page_cache_fill, false)) {
  3519				queue_delayed_work(system_wq,
  3520					&krcp->page_cache_work, PAGE_CACHE_FILL_DELAY);
  3521			} else {
  3522				hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  3523				krcp->hrtimer.function = schedule_page_work_fn;
  3524				hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
  3525			}
  3526		}
  3527	}
  3528	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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