[PATCH AUTOSEL 5.18 39/93] refscale: Convert test_lock spinlock to raw_spinlock

Sasha Levin
2022-08-11T15:57:40Z

From: Zqiang <qiang1.zhang@intel.com>

[ Upstream commit 7bf336fb8dac718febb7bf4fe79e1be0c5e4a631 ]

In kernels built with CONFIG_PREEMPT_RT=y, spinlocks are replaced by
rt_mutex, which can sleep. This means that acquiring a non-raw spinlock
in a critical section where preemption is disabled can trigger the
following BUG:

BUG: scheduling while atomic: ref_scale_reade/76/0x00000002
Preemption disabled at:
ref_lock_section+0x16/0x80
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x82
dump_stack+0x10/0x12
__schedule_bug.cold+0x9c/0xad
__schedule+0x839/0xc00
schedule_rtlock+0x22/0x40
rtlock_slowlock_locked+0x460/0x1350
rt_spin_lock+0x61/0xe0
ref_lock_section+0x29/0x80
rcu_scale_one_reader+0x52/0x60
ref_scale_reader+0x28d/0x490
kthread+0x128/0x150
ret_from_fork+0x22/0x30
</TASK>

This commit therefore converts spinlock to raw_spinlock.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/rcu/refscale.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 5489ff7f478e..12ee5fd6404e 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -365,7 +365,7 @@ static struct ref_scale_ops rwsem_ops = {
};

// Definitions for global spinlock
-static DEFINE_SPINLOCK(test_lock);
+static DEFINE_RAW_SPINLOCK(test_lock);

static void ref_lock_section(const int nloops)
{
@@ -373,8 +373,8 @@ static void ref_lock_section(const int nloops)

preempt_disable();
for (i = nloops; i >= 0; i--) {
- spin_lock(&test_lock);
- spin_unlock(&test_lock);
+ raw_spin_lock(&test_lock);
+ raw_spin_unlock(&test_lock);
}
preempt_enable();
}
@@ -385,9 +385,9 @@ static void ref_lock_delay_section(const int nloops, const int udl, const int nd

preempt_disable();
for (i = nloops; i >= 0; i--) {
- spin_lock(&test_lock);
+ raw_spin_lock(&test_lock);
un_delay(udl, ndl);
- spin_unlock(&test_lock);
+ raw_spin_unlock(&test_lock);
}
preempt_enable();
}
@@ -407,8 +407,8 @@ static void ref_lock_irq_section(const int nloops)

preempt_disable();
for (i = nloops; i >= 0; i--) {
- spin_lock_irqsave(&test_lock, flags);
- spin_unlock_irqrestore(&test_lock, flags);
+ raw_spin_lock_irqsave(&test_lock, flags);
+ raw_spin_unlock_irqrestore(&test_lock, flags);
}
preempt_enable();
}
@@ -420,9 +420,9 @@ static void ref_lock_irq_delay_section(const int nloops, const int udl, const in

preempt_disable();
for (i = nloops; i >= 0; i--) {
- spin_lock_irqsave(&test_lock, flags);
+ raw_spin_lock_irqsave(&test_lock, flags);
un_delay(udl, ndl);
- spin_unlock_irqrestore(&test_lock, flags);
+ raw_spin_unlock_irqrestore(&test_lock, flags);
}
preempt_enable();
}
--
2.35.1