* [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags."
@ 2021-07-02 13:37 Rasmus Villemoes
2021-07-18 12:53 ` Bartosz Golaszewski
2021-07-21 20:25 ` Thomas Gleixner
0 siblings, 2 replies; 3+ messages in thread
From: Rasmus Villemoes @ 2021-07-02 13:37 UTC (permalink / raw)
To: Linus Walleij, Bartosz Golaszewski
Cc: Thomas Gleixner, Song Hui, Rasmus Villemoes, stable, linux-gpio,
linux-kernel
This reverts commit 3d5bfbd9716318b1ca5c38488aa69f64d38a9aa5.
When booting with threadirqs, it causes a splat
WARNING: CPU: 0 PID: 29 at kernel/irq/handle.c:159 __handle_irq_event_percpu+0x1ec/0x27c
irq 66 handler irq_default_primary_handler+0x0/0x1c enabled interrupts
That splat later went away with commit 81e2073c175b ("genirq: Disable
interrupts for force threaded handlers"), which got backported to
-stable. However, when running an -rt kernel, the splat still
exists. Moreover, quoting Thomas Gleixner [1]
But 3d5bfbd97163 ("gpio: mpc8xxx: change the gpio interrupt flags.")
has nothing to do with that:
"Delete the interrupt IRQF_NO_THREAD flags in order to gpio interrupts
can be threaded to allow high-priority processes to preempt."
This changelog is blatantly wrong. In mainline forced irq threads
have always been invoked with softirqs disabled, which obviously
makes them non-preemptible.
So the patch didn't even do what its commit log said.
[1] https://lore.kernel.org/lkml/871r8zey88.ffs@nanos.tec.linutronix.de/
Cc: stable@vger.kernel.org # v5.9+
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
Thomas, please correct me if I misinterpreted your explanation.
drivers/gpio/gpio-mpc8xxx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpio/gpio-mpc8xxx.c b/drivers/gpio/gpio-mpc8xxx.c
index 4b9157a69fca..50b321a1ab1b 100644
--- a/drivers/gpio/gpio-mpc8xxx.c
+++ b/drivers/gpio/gpio-mpc8xxx.c
@@ -405,7 +405,7 @@ static int mpc8xxx_probe(struct platform_device *pdev)
ret = devm_request_irq(&pdev->dev, mpc8xxx_gc->irqn,
mpc8xxx_gpio_irq_cascade,
- IRQF_SHARED, "gpio-cascade",
+ IRQF_NO_THREAD | IRQF_SHARED, "gpio-cascade",
mpc8xxx_gc);
if (ret) {
dev_err(&pdev->dev,
--
2.31.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags."
2021-07-02 13:37 [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags." Rasmus Villemoes
@ 2021-07-18 12:53 ` Bartosz Golaszewski
2021-07-21 20:25 ` Thomas Gleixner
1 sibling, 0 replies; 3+ messages in thread
From: Bartosz Golaszewski @ 2021-07-18 12:53 UTC (permalink / raw)
To: Rasmus Villemoes
Cc: Linus Walleij, Thomas Gleixner, Song Hui, Stable # 4 . 20+,
linux-gpio, LKML
On Fri, Jul 2, 2021 at 3:37 PM Rasmus Villemoes
<linux@rasmusvillemoes.dk> wrote:
>
> This reverts commit 3d5bfbd9716318b1ca5c38488aa69f64d38a9aa5.
>
> When booting with threadirqs, it causes a splat
>
> WARNING: CPU: 0 PID: 29 at kernel/irq/handle.c:159 __handle_irq_event_percpu+0x1ec/0x27c
> irq 66 handler irq_default_primary_handler+0x0/0x1c enabled interrupts
>
> That splat later went away with commit 81e2073c175b ("genirq: Disable
> interrupts for force threaded handlers"), which got backported to
> -stable. However, when running an -rt kernel, the splat still
> exists. Moreover, quoting Thomas Gleixner [1]
>
> But 3d5bfbd97163 ("gpio: mpc8xxx: change the gpio interrupt flags.")
> has nothing to do with that:
>
> "Delete the interrupt IRQF_NO_THREAD flags in order to gpio interrupts
> can be threaded to allow high-priority processes to preempt."
>
> This changelog is blatantly wrong. In mainline forced irq threads
> have always been invoked with softirqs disabled, which obviously
> makes them non-preemptible.
>
> So the patch didn't even do what its commit log said.
>
> [1] https://lore.kernel.org/lkml/871r8zey88.ffs@nanos.tec.linutronix.de/
>
> Cc: stable@vger.kernel.org # v5.9+
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
Applied for fixes, thanks!
Bartosz
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags."
2021-07-02 13:37 [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags." Rasmus Villemoes
2021-07-18 12:53 ` Bartosz Golaszewski
@ 2021-07-21 20:25 ` Thomas Gleixner
1 sibling, 0 replies; 3+ messages in thread
From: Thomas Gleixner @ 2021-07-21 20:25 UTC (permalink / raw)
To: Rasmus Villemoes, Linus Walleij, Bartosz Golaszewski
Cc: Song Hui, Rasmus Villemoes, stable, linux-gpio, linux-kernel
On Fri, Jul 02 2021 at 15:37, Rasmus Villemoes wrote:
> This reverts commit 3d5bfbd9716318b1ca5c38488aa69f64d38a9aa5.
>
> When booting with threadirqs, it causes a splat
>
> WARNING: CPU: 0 PID: 29 at kernel/irq/handle.c:159 __handle_irq_event_percpu+0x1ec/0x27c
> irq 66 handler irq_default_primary_handler+0x0/0x1c enabled interrupts
>
> That splat later went away with commit 81e2073c175b ("genirq: Disable
> interrupts for force threaded handlers"), which got backported to
> -stable. However, when running an -rt kernel, the splat still
> exists. Moreover, quoting Thomas Gleixner [1]
>
> But 3d5bfbd97163 ("gpio: mpc8xxx: change the gpio interrupt flags.")
> has nothing to do with that:
>
> "Delete the interrupt IRQF_NO_THREAD flags in order to gpio interrupts
> can be threaded to allow high-priority processes to preempt."
>
> This changelog is blatantly wrong. In mainline forced irq threads
> have always been invoked with softirqs disabled, which obviously
> makes them non-preemptible.
>
> So the patch didn't even do what its commit log said.
>
> [1] https://lore.kernel.org/lkml/871r8zey88.ffs@nanos.tec.linutronix.de/
>
> Cc: stable@vger.kernel.org # v5.9+
> Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> ---
> Thomas, please correct me if I misinterpreted your explanation.
Nothing to correct here.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-07-02 13:37 [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags." Rasmus Villemoes
2021-07-18 12:53 ` Bartosz Golaszewski
2021-07-21 20:25 ` Thomas Gleixner
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