linux-kernel - Re: [rcutorture] 613b00fbe6: WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_fwd_prog

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Message-ID: <20220831105707.GJ6159@paulmck-ThinkPad-P17-Gen-1>
Date:   Wed, 31 Aug 2022 03:57:07 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     kernel test robot <oliver.sang@...el.com>
Cc:     Neeraj Upadhyay <neeraj.iitr10@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...ts.01.org,
        lkp@...el.com, qiang1.zhang@...el.com
Subject: Re: [rcutorture]  613b00fbe6:
 WARNING:at_kernel/rcu/rcutorture.c:#rcu_torture_fwd_prog_cr[rcutorture]

On Wed, Aug 03, 2022 at 11:05:12PM +0800, kernel test robot wrote:
> 
> (please be noted we reported this since clean on parent, ~10% on this commit,
> and found similar issue on latest maineline, e.g. v5.19)
> 
> 
> Greeting,
> 
> FYI, we noticed the following commit (built with gcc-11):
> 
> commit: 613b00fbe64461f1c73e035e07c22cf3de65740b ("rcutorture: Add ability to limit callback-flood intensity")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> in testcase: rcutorture
> version: 
> with following parameters:
> 
> 	runtime: 300s
> 	test: default
> 	torture_type: tasks-tracing
> 
> test-description: rcutorture is rcutorture kernel module load/unload test.
> test-url: https://www.kernel.org/doc/Documentation/RCU/torture.txt
> 
> 
> on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

I believe that this commit in -rcu fixes this problem.  Could you please
check it?

							Thanx, Paul

------------------------------------------------------------------------

commit dba268ff32101559cd3e3800b24993ae5c59844c
Author: Zqiang <qiang1.zhang@...el.com>
Date:   Sun Jul 31 18:53:56 2022 +0800

    rcutorture: Use the barrier operation specified by cur_ops
    
    The rcutorture_oom_notify() function unconditionally invokes
    rcu_barrier(), which is OK when the rcutorture.torture_type value is
    "rcu", but unhelpful otherwise.  The purpose of these barrier calls is to
    wait for all outstanding callback-flooding callbacks to be invoked before
    cleaning up their data.  Using the wrong barrier function therefore
    risks arbitrary memory corruption.  Thus, this commit changes these
    rcu_barrier() calls into cur_ops->cb_barrier() to make things work when
    torturing non-vanilla flavors of RCU.
    
    Signed-off-by: Zqiang <qiang1.zhang@...el.com>
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7168dc8d61e98..bdd630f7a970c 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2603,12 +2603,12 @@ static int rcutorture_oom_notify(struct notifier_block *self,
 	for (i = 0; i < fwd_progress; i++)
 		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
 	pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
-	rcu_barrier();
+	cur_ops->cb_barrier();
 	ncbs = 0;
 	for (i = 0; i < fwd_progress; i++)
 		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
 	pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
-	rcu_barrier();
+	cur_ops->cb_barrier();
 	ncbs = 0;
 	for (i = 0; i < fwd_progress; i++)
 		ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);