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Message-ID: <202208251224.teVMa7Yy-lkp@intel.com>
Date: Thu, 25 Aug 2022 12:30:10 +0800
From: kernel test robot <lkp@...el.com>
To: Uros Bizjak <ubizjak@...il.com>
Cc: llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
Ammar Faizi <ammarfaizi2@...weeb.org>,
GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Memory Management List <linux-mm@...ck.org>
Subject: [ammarfaizi2-block:akpm/mm/mm-nonmm-unstable 50/50]
kernel/smpboot.c:435:6: warning: variable 'oldstate' is used uninitialized
whenever 'if' condition is true
Hi Uros,
FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.
tree: https://github.com/ammarfaizi2/linux-block akpm/mm/mm-nonmm-unstable
head: 2d1e07c7534c14e56ac3818fa24e7c1643a9b1dc
commit: 2d1e07c7534c14e56ac3818fa24e7c1643a9b1dc [50/50] smpboot: use atomic_try_cmpxchg in cpu_wait_death and cpu_report_death
config: x86_64-randconfig-a003 (https://download.01.org/0day-ci/archive/20220825/202208251224.teVMa7Yy-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
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
# https://github.com/ammarfaizi2/linux-block/commit/2d1e07c7534c14e56ac3818fa24e7c1643a9b1dc
git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block
git fetch --no-tags ammarfaizi2-block akpm/mm/mm-nonmm-unstable
git checkout 2d1e07c7534c14e56ac3818fa24e7c1643a9b1dc
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@...el.com>
All warnings (new ones prefixed by >>):
>> kernel/smpboot.c:435:6: warning: variable 'oldstate' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/smpboot.c:449:6: note: uninitialized use occurs here
if (oldstate == CPU_DEAD) {
^~~~~~~~
kernel/smpboot.c:435:2: note: remove the 'if' if its condition is always false
if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/smpboot.c:428:14: note: initialize the variable 'oldstate' to silence this warning
int oldstate;
^
= 0
1 warning generated.
vim +435 kernel/smpboot.c
8038dad7e88858 Paul E. McKenney 2015-02-25 421
8038dad7e88858 Paul E. McKenney 2015-02-25 422 /*
8038dad7e88858 Paul E. McKenney 2015-02-25 423 * Wait for the specified CPU to exit the idle loop and die.
8038dad7e88858 Paul E. McKenney 2015-02-25 424 */
8038dad7e88858 Paul E. McKenney 2015-02-25 425 bool cpu_wait_death(unsigned int cpu, int seconds)
8038dad7e88858 Paul E. McKenney 2015-02-25 426 {
8038dad7e88858 Paul E. McKenney 2015-02-25 427 int jf_left = seconds * HZ;
8038dad7e88858 Paul E. McKenney 2015-02-25 428 int oldstate;
8038dad7e88858 Paul E. McKenney 2015-02-25 429 bool ret = true;
8038dad7e88858 Paul E. McKenney 2015-02-25 430 int sleep_jf = 1;
8038dad7e88858 Paul E. McKenney 2015-02-25 431
8038dad7e88858 Paul E. McKenney 2015-02-25 432 might_sleep();
8038dad7e88858 Paul E. McKenney 2015-02-25 433
8038dad7e88858 Paul E. McKenney 2015-02-25 434 /* The outgoing CPU will normally get done quite quickly. */
8038dad7e88858 Paul E. McKenney 2015-02-25 @435 if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
8038dad7e88858 Paul E. McKenney 2015-02-25 436 goto update_state;
8038dad7e88858 Paul E. McKenney 2015-02-25 437 udelay(5);
8038dad7e88858 Paul E. McKenney 2015-02-25 438
8038dad7e88858 Paul E. McKenney 2015-02-25 439 /* But if the outgoing CPU dawdles, wait increasingly long times. */
8038dad7e88858 Paul E. McKenney 2015-02-25 440 while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
8038dad7e88858 Paul E. McKenney 2015-02-25 441 schedule_timeout_uninterruptible(sleep_jf);
8038dad7e88858 Paul E. McKenney 2015-02-25 442 jf_left -= sleep_jf;
8038dad7e88858 Paul E. McKenney 2015-02-25 443 if (jf_left <= 0)
8038dad7e88858 Paul E. McKenney 2015-02-25 444 break;
8038dad7e88858 Paul E. McKenney 2015-02-25 445 sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
8038dad7e88858 Paul E. McKenney 2015-02-25 446 }
8038dad7e88858 Paul E. McKenney 2015-02-25 447 oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
2d1e07c7534c14 Uros Bizjak 2022-08-23 448 update_state:
8038dad7e88858 Paul E. McKenney 2015-02-25 449 if (oldstate == CPU_DEAD) {
8038dad7e88858 Paul E. McKenney 2015-02-25 450 /* Outgoing CPU died normally, update state. */
8038dad7e88858 Paul E. McKenney 2015-02-25 451 smp_mb(); /* atomic_read() before update. */
8038dad7e88858 Paul E. McKenney 2015-02-25 452 atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
8038dad7e88858 Paul E. McKenney 2015-02-25 453 } else {
8038dad7e88858 Paul E. McKenney 2015-02-25 454 /* Outgoing CPU still hasn't died, set state accordingly. */
2d1e07c7534c14 Uros Bizjak 2022-08-23 455 if (!atomic_try_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
2d1e07c7534c14 Uros Bizjak 2022-08-23 456 &oldstate, CPU_BROKEN))
8038dad7e88858 Paul E. McKenney 2015-02-25 457 goto update_state;
8038dad7e88858 Paul E. McKenney 2015-02-25 458 ret = false;
8038dad7e88858 Paul E. McKenney 2015-02-25 459 }
8038dad7e88858 Paul E. McKenney 2015-02-25 460 return ret;
8038dad7e88858 Paul E. McKenney 2015-02-25 461 }
8038dad7e88858 Paul E. McKenney 2015-02-25 462
:::::: The code at line 435 was first introduced by commit
:::::: 8038dad7e888581266c76df15d70ca457a3c5910 smpboot: Add common code for notification from dying CPU
:::::: TO: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
:::::: CC: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
--
0-DAY CI Kernel Test Service
https://01.org/lkp
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