Restore the check if an IRQ chip implements the irq_ack function prior
to its invocation. Commit 22a49163e90d ("genirq: Provide compat handling
for chip->ack()") removed the check from handle_edge_irq while keeping
the check in other call paths.
Signed-off-by: Adrian-Ken Rueegsegger <[email protected]>
---
kernel/irq/chip.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index eb9a4ea..3889b02 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -586,7 +586,8 @@ handle_edge_irq(unsigned int irq, struct irq_desc *desc)
kstat_incr_irqs_this_cpu(irq, desc);
/* Start handling the irq */
- desc->irq_data.chip->irq_ack(&desc->irq_data);
+ if (desc->irq_data.chip->irq_ack)
+ desc->irq_data.chip->irq_ack(&desc->irq_data);
do {
if (unlikely(!desc->action)) {
--
1.7.10.4
On Tue, 14 Apr 2015, Adrian-Ken Rueegsegger wrote:
> Restore the check if an IRQ chip implements the irq_ack function prior
> to its invocation. Commit 22a49163e90d ("genirq: Provide compat handling
> for chip->ack()") removed the check from handle_edge_irq while keeping
> the check in other call paths.
How's an edge triggered interrupt without ack supposed to work?
You are missing to describe which problem you solve.
Thanks,
tglx
> Signed-off-by: Adrian-Ken Rueegsegger <[email protected]>
> ---
> kernel/irq/chip.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index eb9a4ea..3889b02 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -586,7 +586,8 @@ handle_edge_irq(unsigned int irq, struct irq_desc *desc)
> kstat_incr_irqs_this_cpu(irq, desc);
>
> /* Start handling the irq */
> - desc->irq_data.chip->irq_ack(&desc->irq_data);
> + if (desc->irq_data.chip->irq_ack)
> + desc->irq_data.chip->irq_ack(&desc->irq_data);
>
> do {
> if (unlikely(!desc->action)) {
> --
> 1.7.10.4
>
>
Hi,
On 04/14/2015 08:00 PM, Thomas Gleixner wrote:
> On Tue, 14 Apr 2015, Adrian-Ken Rueegsegger wrote:
>> Restore the check if an IRQ chip implements the irq_ack function prior
>> to its invocation. Commit 22a49163e90d ("genirq: Provide compat handling
>> for chip->ack()") removed the check from handle_edge_irq while keeping
>> the check in other call paths.
>
> How's an edge triggered interrupt without ack supposed to work?
>
> You are missing to describe which problem you solve.
I am running Linux as a VM on top of the Muen Separation Kernel (SK)
[1], where we have implemented PCI device passthrough using VT-d. In
this case the hardware interrupt is handled by the SK/hypervisor and
injected to Linux.
To support PCI MSI(-X), we register our own platform-specific MSI
operations (x86_msi.setup_msi_irqs, etc) and implement an irq_chip that
simply provides the irq_mask and irq_unmask operations (by reusing the
"regular" mask_msi_irq/unmask_msi_irq).
After encountering a null pointer dereference due to the irq_chip not
providing an irq_ack operation, I examined the commit that changed the
source of the irq_ack call, noticing that only the check in
handle_edge_irq was dropped while the other call sites were kept. As the
commit message did not provide me with additional information for that
particular fragment of the change, I (prematurely) concluded that it was
not intentional.
If it is a prerequisite for IRQ chips to provide the irq_ack operation
when used in conjunction with handle_edge_irq, then please ignore my
patch. In that case, I will adjust our chip implementation
accordingly.
Thanks for your time,
Adrian
[1] - http://muen.codelabs.ch/
On Wed, 15 Apr 2015, Adrian-Ken Rueegsegger wrote:
> To support PCI MSI(-X), we register our own platform-specific MSI
> operations (x86_msi.setup_msi_irqs, etc) and implement an irq_chip that
> simply provides the irq_mask and irq_unmask operations (by reusing the
> "regular" mask_msi_irq/unmask_msi_irq).
But why are you using the edge flow handler then?
> After encountering a null pointer dereference due to the irq_chip not
> providing an irq_ack operation, I examined the commit that changed the
> source of the irq_ack call, noticing that only the check in
> handle_edge_irq was dropped while the other call sites were kept. As the
> commit message did not provide me with additional information for that
> particular fragment of the change, I (prematurely) concluded that it was
> not intentional.
>
> If it is a prerequisite for IRQ chips to provide the irq_ack operation
> when used in conjunction with handle_edge_irq, then please ignore my
> patch. In that case, I will adjust our chip implementation
> accordingly.
Yes, it is more or less. And I really want to avoid the extra
conditional in the handler hotpath.
Thanks,