This function calls .irq_eoi in three places, making the logic hard to
follow. Rearrange the function so that .irq_eoi is called only once.
The only time .irq_eoi is not called is when all three if checks fail,
so return early in that case. threads_oneshot can only be nonzero if
IRQS_ONESHOT is set, so the IRQS_ONESHOT check can be omitted there.
The IRQS_ONESHOT condition from the first if statement must then be
copied to the unmask_irq() condition.
Furthermore, if IRQS_ONESHOT is set, mask_irq() must have been called
in the parent function, so the irqd_irq_masked() check is redundant.
Signed-off-by: Samuel Holland <[email protected]>
---
kernel/irq/chip.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 8ac37e8e738a..672bad021a1f 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -658,10 +658,15 @@ EXPORT_SYMBOL_GPL(handle_level_irq);
static void cond_unmask_eoi_irq(struct irq_desc *desc, struct irq_chip *chip)
{
- if (!(desc->istate & IRQS_ONESHOT)) {
- chip->irq_eoi(&desc->irq_data);
+ /*
+ * Do not send an EOI if the thread will do it later in
+ * unmask_threaded_irq().
+ */
+ if ((chip->flags & IRQCHIP_EOI_THREADED) && desc->threads_oneshot)
return;
- }
+
+ chip->irq_eoi(&desc->irq_data);
+
/*
* We need to unmask in the following cases:
* - Oneshot irq which did not wake the thread (caused by a
@@ -669,12 +674,8 @@ static void cond_unmask_eoi_irq(struct irq_desc *desc, struct irq_chip *chip)
* completely).
*/
if (!irqd_irq_disabled(&desc->irq_data) &&
- irqd_irq_masked(&desc->irq_data) && !desc->threads_oneshot) {
- chip->irq_eoi(&desc->irq_data);
+ (desc->istate & IRQS_ONESHOT) && !desc->threads_oneshot)
unmask_irq(desc);
- } else if (!(chip->flags & IRQCHIP_EOI_THREADED)) {
- chip->irq_eoi(&desc->irq_data);
- }
}
/**
--
2.37.4
Samuel!
On Sat, Nov 26 2022 at 17:41, Samuel Holland wrote:
> This function calls .irq_eoi in three places, making the logic hard to
> follow. Rearrange the function so that .irq_eoi is called only once.
>
> The only time .irq_eoi is not called is when all three if checks fail,
> so return early in that case. threads_oneshot can only be nonzero if
> IRQS_ONESHOT is set, so the IRQS_ONESHOT check can be omitted there.
>
> The IRQS_ONESHOT condition from the first if statement must then be
> copied to the unmask_irq() condition.
>
> Furthermore, if IRQS_ONESHOT is set, mask_irq() must have been called
> in the parent function, so the irqd_irq_masked() check is redundant.
Not really convinced that all this is functionaly equivalent.
> static void cond_unmask_eoi_irq(struct irq_desc *desc, struct irq_chip *chip)
> {
> - if (!(desc->istate & IRQS_ONESHOT)) {
> - chip->irq_eoi(&desc->irq_data);
> + /*
> + * Do not send an EOI if the thread will do it later in
> + * unmask_threaded_irq().
> + */
> + if ((chip->flags & IRQCHIP_EOI_THREADED) && desc->threads_oneshot)
> return;
> - }
> +
> + chip->irq_eoi(&desc->irq_data);
This now issues EOI when the interrupt is in disabled state, which was
not done before. That's probably a non-issue, but clearly a undocumented
change.
> +
> /*
> * We need to unmask in the following cases:
> * - Oneshot irq which did not wake the thread (caused by a
> @@ -669,12 +674,8 @@ static void cond_unmask_eoi_irq(struct irq_desc *desc, struct irq_chip *chip)
> * completely).
> */
> if (!irqd_irq_disabled(&desc->irq_data) &&
> - irqd_irq_masked(&desc->irq_data) && !desc->threads_oneshot) {
> - chip->irq_eoi(&desc->irq_data);
> + (desc->istate & IRQS_ONESHOT) && !desc->threads_oneshot)
> unmask_irq(desc);
This breaks the mask logic of handle_fasteoi_mask_irq() for an interrupt
which does not have IRQS_ONESHOT set.
So no, it's not the same and it even breaks stuff.
Thanks,
tglx
On Wed, Nov 30 2022 at 15:48, Thomas Gleixner wrote:
> On Sat, Nov 26 2022 at 17:41, Samuel Holland wrote:
>> + (desc->istate & IRQS_ONESHOT) && !desc->threads_oneshot)
>> unmask_irq(desc);
>
> This breaks the mask logic of handle_fasteoi_mask_irq() for an interrupt
> which does not have IRQS_ONESHOT set.
Ignore this one. That handler is broken by design.