linux-kernel - [rcu:dev.2020.06.17a 35/38] kernel/sched/core.c:2650 try_to_wake

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Date:   Mon, 22 Jun 2020 15:11:17 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Peter Zijlstra <peterz@...radead.org>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [rcu:dev.2020.06.17a 35/38] kernel/sched/core.c:2650
 try_to_wake_up() error: uninitialized symbol 'cpu'.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2020.06.17a
head:   d3779e78b9848a707448dbb4a0cb6c4bb651fe9c
commit: 59a5d883f2ccdce1700862b5983cfd3473630aea [35/38] EXP sched: Alleged fix for v5.8 merge-window scheduler issue
config: x86_64-randconfig-m001-20200621 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-13) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

smatch warnings:
kernel/sched/core.c:2650 try_to_wake_up() error: uninitialized symbol 'cpu'.

# https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?id=59a5d883f2ccdce1700862b5983cfd3473630aea
git remote add rcu https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
git remote update rcu
git checkout 59a5d883f2ccdce1700862b5983cfd3473630aea
vim +/cpu +2650 kernel/sched/core.c

^1da177e4c3f41 kernel/sched.c      Linus Torvalds 2005-04-16  2644  
b5179ac70de85e kernel/sched/core.c Peter Zijlstra 2016-05-11  2645  	ttwu_queue(p, cpu, wake_flags);
aacedf26fb7601 kernel/sched/core.c Peter Zijlstra 2019-06-07  2646  unlock:
013fdb8086acaa kernel/sched.c      Peter Zijlstra 2011-04-05  2647  	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
aacedf26fb7601 kernel/sched/core.c Peter Zijlstra 2019-06-07  2648  out:
aacedf26fb7601 kernel/sched/core.c Peter Zijlstra 2019-06-07  2649  	if (success)
aacedf26fb7601 kernel/sched/core.c Peter Zijlstra 2019-06-07 @2650  		ttwu_stat(p, cpu, wake_flags);
                                                                                             ^^^
This can be uninitialized on a couple "goto unlock;" paths.  Lines
2581 and 2622.  The KASan tool will warn about this at run time as well.
I'm not sure why the build bot doesn't include the whole function for
this bug report...

e3d85487fba422 kernel/sched/core.c Peter Zijlstra 2019-07-10  2651  	preempt_enable();
^1da177e4c3f41 kernel/sched.c      Linus Torvalds 2005-04-16  2652  
^1da177e4c3f41 kernel/sched.c      Linus Torvalds 2005-04-16  2653  	return success;
^1da177e4c3f41 kernel/sched.c      Linus Torvalds 2005-04-16  2654  }

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