| Message ID | 20221126234134.32660-2-samuel@sholland.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | genirq: oneshot-safe threaded EOIs | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/tree_selection | fail | Guessing tree name failed |
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.
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); - } } /**
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 <samuel@sholland.org> --- kernel/irq/chip.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)