From:   Zqiang <qiang1.zhang@intel.com>
To:     paulmck@kernel.org, frederic@kernel.org, joel@joelfernandes.org
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] rcutorture: Convert schedule_timeout_uninterruptible() to mdelay() in rcu_torture_stall()
Date:   Mon, 20 Mar 2023 11:24:22 +0800
Message-Id: <20230320032422.4010801-1-qiang1.zhang@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

For kernels built with enable PREEMPT_NONE and CONFIG_DEBUG_ATOMIC_SLEEP,
running the RCU stall tests.

runqemu kvm slirp nographic qemuparams="-m 1024 -smp 4"
bootparams="nokaslr console=ttyS0 rcutorture.stall_cpu=30
rcutorture.stall_no_softlockup=1 rcutorture.stall_cpu_irqsoff=1
rcutorture.stall_cpu_block=1" -d

[   10.841071] rcu-torture: rcu_torture_stall begin CPU stall
[   10.841073] rcu_torture_stall start on CPU 3.
[   10.841077] BUG: scheduling while atomic: rcu_torture_sta/66/0x0000000
....
[   10.841108] Call Trace:
[   10.841110]  <TASK>
[   10.841112]  dump_stack_lvl+0x64/0xb0
[   10.841118]  dump_stack+0x10/0x20
[   10.841121]  __schedule_bug+0x8b/0xb0
[   10.841126]  __schedule+0x2172/0x2940
[   10.841157]  schedule+0x9b/0x150
[   10.841160]  schedule_timeout+0x2e8/0x4f0
[   10.841192]  schedule_timeout_uninterruptible+0x47/0x50
[   10.841195]  rcu_torture_stall+0x2e8/0x300
[   10.841199]  kthread+0x175/0x1a0
[   10.841206]  ret_from_fork+0x2c/0x50

The above calltrace occurs in the local_irq_disable/enable() critical
section call schedule_timeout(), and invoke schedule_timeout() also
implies a quiescent state, of course it also fails to trigger RCU stall,
this commit therefore use mdelay() instead of schedule_timeout() to
trigger RCU stall.

Suggested-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
---
 kernel/rcu/rcutorture.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index d06c2da04c34..a08a72bef5f1 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2472,7 +2472,7 @@ static int rcu_torture_stall(void *args)
 #ifdef CONFIG_PREEMPTION
 				preempt_schedule();
 #else
-				schedule_timeout_uninterruptible(HZ);
+				mdelay(jiffies_to_msecs(HZ));
 #endif
 			} else if (stall_no_softlockup) {
 				touch_softlockup_watchdog();
-- 
2.25.1