On Sun, Jun 12, 2022 at 10:02:25AM +0800, Zqiang wrote:
> In PREEMPT_RT kernel, the spinlock are replaced by sleepable rt_mutex.
> in a critical section where preemption is disabled this will trigger
> calltrace like the following:
>
> 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>
>
> Convert spinlock to raw_spinlock to fix it.
>
> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
Queued for review and testing, thank you!
And as usual, wordsmithed, so could you please check for anything
that I might have messed up?
Thanx, Paul
------------------------------------------------------------------------
commit 0c284371063996f09c0b5e3d0f4c7dff8e966d86
Author: Zqiang <qiang1.zhang@xxxxxxxxx>
Date: Sun Jun 12 10:02:25 2022 +0800
refscale: Convert test_lock spinlock to raw_spinlock
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@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index 909644abee67f..435c884c02b5c 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -385,7 +385,7 @@ 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)
{
@@ -393,8 +393,8 @@ 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();
}
@@ -405,9 +405,9 @@ 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();
}
@@ -427,8 +427,8 @@ 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();
}
@@ -440,9 +440,9 @@ 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();
}
