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Subject[tip:irq/urgent] x86, irq: Remove IRQ_DISABLED check in process context IRQ move
Commit-ID:  6ec3cfeca04622e3d80c9270191cd7f5f88214af
Gitweb: http://git.kernel.org/tip/6ec3cfeca04622e3d80c9270191cd7f5f88214af
Author: Pallipadi, Venkatesh <venkatesh.pallipadi@intel.com>
AuthorDate: Mon, 13 Apr 2009 15:20:58 -0700
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 14 Apr 2009 15:21:13 +0200

x86, irq: Remove IRQ_DISABLED check in process context IRQ move

As discussed in the thread here:

http://marc.info/?l=linux-kernel&m=123964468521142&w=2

Eric W. Biederman observed:

> It looks like some additional bugs have slipped in since last I looked.
>
> set_irq_affinity does this:
> ifdef CONFIG_GENERIC_PENDING_IRQ
> if (desc->status & IRQ_MOVE_PCNTXT || desc->status & IRQ_DISABLED) {
> cpumask_copy(desc->affinity, cpumask);
> desc->chip->set_affinity(irq, cpumask);
> } else {
> desc->status |= IRQ_MOVE_PENDING;
> cpumask_copy(desc->pending_mask, cpumask);
> }
> #else
>
> That IRQ_DISABLED case is a software state and as such it has nothing to
> do with how safe it is to move an irq in process context.

[...]

>
> The only reason we migrate MSIs in interrupt context today is that there
> wasn't infrastructure for support migration both in interrupt context
> and outside of it.

Yes. The idea here was to force the MSI migration to happen in process
context. One of the patches in the series did

disable_irq(dev->irq);
irq_set_affinity(dev->irq, cpumask_of(dev->cpu));
enable_irq(dev->irq);

with the above patch adding irq/manage code check for interrupt disabled
and moving the interrupt in process context.

IIRC, there was no IRQ_MOVE_PCNTXT when we were developing this HPET
code and we ended up having this ugly hack. IRQ_MOVE_PCNTXT was there
when we eventually submitted the patch upstream. But, looks like I did a
blind rebasing instead of using IRQ_MOVE_PCNTXT in hpet MSI code.

Below patch fixes this. i.e., revert commit 932775a4ab622e3c99bd59f14cc
and add PCNTXT to HPET MSI setup. Also removes copying of desc->affinity
in generic code as set_affinity routines are doing it internally.

Reported-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Li Shaohua" <shaohua.li@intel.com>
Cc: Gary Hade <garyhade@us.ibm.com>
Cc: "lcm@us.ibm.com" <lcm@us.ibm.com>
Cc: suresh.b.siddha@intel.com
LKML-Reference: <20090413222058.GB8211@linux-os.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
arch/x86/kernel/apic/io_apic.c | 2 ++
kernel/irq/manage.c | 5 ++---
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index a2789e4..30da617 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3670,12 +3670,14 @@ int arch_setup_hpet_msi(unsigned int irq)
{
int ret;
struct msi_msg msg;
+ struct irq_desc *desc = irq_to_desc(irq);

ret = msi_compose_msg(NULL, irq, &msg);
if (ret < 0)
return ret;

hpet_msi_write(irq, &msg);
+ desc->status |= IRQ_MOVE_PCNTXT;
set_irq_chip_and_handler_name(irq, &hpet_msi_type, handle_edge_irq,
"edge");

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 7e2e7dd..2734eca 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -109,10 +109,9 @@ int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask)
spin_lock_irqsave(&desc->lock, flags);

#ifdef CONFIG_GENERIC_PENDING_IRQ
- if (desc->status & IRQ_MOVE_PCNTXT || desc->status & IRQ_DISABLED) {
- cpumask_copy(desc->affinity, cpumask);
+ if (desc->status & IRQ_MOVE_PCNTXT)
desc->chip->set_affinity(irq, cpumask);
- } else {
+ else {
desc->status |= IRQ_MOVE_PENDING;
cpumask_copy(desc->pending_mask, cpumask);
}

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