Re: [PATCH v3 1/4] rcutorture: Don't disable softirqs with preemption disabled when PREEMPT_RT

Sebastian Andrzej Siewior
2021-08-17T13:17:48Z

On 2021-08-17 14:13:47 [+0200], To Valentin Schneider wrote:
> > index eecd1caef71d..4f3db1d3170d 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -1548,6 +1548,8 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
> > * them on non-RT.
> > */
> > if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
> > + /* Can't disable bh in atomic context under PREEMPT_RT */
> > + mask &= ~(RCUTORTURE_RDR_ATOM_BH | RCUTORTURE_RDR_ATOM_RBH);
>
> Let me stare at this…

I would fold this

--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1549,6 +1549,13 @@ rcutorture_extend_mask(int oldmask, stru
*/
if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
/*
+ * Can't disable bh in atomic context if bh was already
+ * disabled by another task on the same CPU. Instead of
+ * attempting to track this, just avoid disabling bh in atomic
+ * context.
+ */
+ mask &= ~atomic_bhs;
+ /*
* Can't release the outermost rcu lock in an irq disabled
* section without preemption also being disabled, if irqs
* had ever been enabled during this RCU critical section
@@ -1559,16 +1566,6 @@ rcutorture_extend_mask(int oldmask, stru
!(mask & preempts))
mask |= RCUTORTURE_RDR_RCU;

- /* Can't modify atomic bh in non-atomic context */
- if ((oldmask & atomic_bhs) && (mask & atomic_bhs) &&
- !(mask & preempts_irq)) {
- mask |= oldmask & preempts_irq;
- if (mask & RCUTORTURE_RDR_IRQ)
- mask |= oldmask & tmp;
- }
- if ((mask & atomic_bhs) && !(mask & preempts_irq))
- mask |= RCUTORTURE_RDR_PREEMPT;
-
/* Can't modify non-atomic bh in atomic context */
tmp = nonatomic_bhs;
if (oldmask & preempts_irq)

into the original patch and forward it upstream…

Sebastian