[PATCH] tty/hvc: Use IRQF_SHARED for hvc consoles

[PATCH] tty/hvc: Use IRQF_SHARED for hvc consoles

[Samuel Mendoza-Jonas]

Commit 2def86a7200c
("hvc: Convert to using interrupts instead of opal events")
enabled the use of interrupts in the hvc_driver for OPAL platforms.
However on machines with more than one hvc console, any console after
the first will fail to register an interrupt handler in
notifier_add_irq() since all consoles share the same IRQ number but do
not set the IRQF_SHARED flag:

[   51.179907] genirq: Flags mismatch irq 31. 00000000 (hvc_console) vs.
00000000 (hvc_console)
[   51.180010] hvc_open: request_irq failed with rc -16.

This error propagates up to hvc_open() and the console is closed, but
OPAL will still generate interrupts that are not handled, leading to
rcu_sched stall warnings.

Set IRQF_SHARED when calling request_irq, allowing additional consoles
to start properly.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Cc: <stable@vger.kernel.org> # 4.1.x-
---
 drivers/tty/hvc/hvc_irq.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/hvc/hvc_irq.c b/drivers/tty/hvc/hvc_irq.c
index c9adb05..621263a 100644
--- a/drivers/tty/hvc/hvc_irq.c
+++ b/drivers/tty/hvc/hvc_irq.c
@@ -14,6 +14,9 @@ static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance)
 	/* if hvc_poll request a repoll, then kick the hvcd thread */
 	if (hvc_poll(dev_instance))
 		hvc_kick();
+	/* We're safe to always return IRQ_HANDLED as the hvcd thread will
+	 * iterate through each hvc_struct
+	 */
 	return IRQ_HANDLED;
 }
 
@@ -28,7 +31,7 @@ int notifier_add_irq(struct hvc_struct *hp, int irq)
 		hp->irq_requested = 0;
 		return 0;
 	}
-	rc = request_irq(irq, hvc_handle_interrupt, 0,
+	rc = request_irq(irq, hvc_handle_interrupt, IRQF_SHARED,
 			   "hvc_console", hp);
 	if (!rc)
 		hp->irq_requested = 1;
-- 
2.7.3

Re: [PATCH] tty/hvc: Use IRQF_SHARED for hvc consoles

[Stewart Smith]

Samuel Mendoza-Jonas <sam@mendozajonas.com> writes:
> Commit 2def86a7200c
> ("hvc: Convert to using interrupts instead of opal events")
> enabled the use of interrupts in the hvc_driver for OPAL platforms.
> However on machines with more than one hvc console, any console after
> the first will fail to register an interrupt handler in
> notifier_add_irq() since all consoles share the same IRQ number but do
> not set the IRQF_SHARED flag:
>
> [   51.179907] genirq: Flags mismatch irq 31. 00000000 (hvc_console) vs.
> 00000000 (hvc_console)
> [   51.180010] hvc_open: request_irq failed with rc -16.
>
> This error propagates up to hvc_open() and the console is closed, but
> OPAL will still generate interrupts that are not handled, leading to
> rcu_sched stall warnings.
>
> Set IRQF_SHARED when calling request_irq, allowing additional consoles
> to start properly.
>
> Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
> Cc: <stable@vger.kernel.org> # 4.1.x-

Tested on 4.4.6 - seemed to stop (some of) the problems I was having
when using it as a kernel for the bootloader on a FSP based POWER8
system.

Tested-by: Stewart Smith <stewart@linux.vnet.ibm.com>

-- 
Stewart Smith
OPAL Architect, IBM.