[PATCH] Add SA_PERCPU_IRQ flag support

[PATCH] Add SA_PERCPU_IRQ flag support

[Dimitri Sivanich]

The generic request_irq/setup_irq code should support the SA_PERCPU_IRQ flag.

Not sure why it was left out, but this patch adds that support.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>

Index: linux/kernel/irq/manage.c
=================================--- linux.orig/kernel/irq/manage.c	2006-03-16 14:05:27.957927445 -0600
+++ linux/kernel/irq/manage.c	2006-03-16 14:06:02.283661867 -0600
@@ -201,6 +201,9 @@ int setup_irq(unsigned int irq, struct i
 	 * The following block of code has to be executed atomically
 	 */
 	spin_lock_irqsave(&desc->lock,flags);
+	if (new->flags & SA_PERCPU_IRQ) {
+		desc->status |= IRQ_PER_CPU;
+	}
 	p = &desc->action;
 	if ((old = *p) != NULL) {
 		/* Can't share interrupts unless both agree to */

Re: [PATCH] Add SA_PERCPU_IRQ flag support

[Christoph Hellwig]

On Thu, Mar 16, 2006 at 06:31:14PM -0600, Dimitri Sivanich wrote:
> The generic request_irq/setup_irq code should support the SA_PERCPU_IRQ flag.
> 
> Not sure why it was left out, but this patch adds that support.
> 
> Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
> 
> Index: linux/kernel/irq/manage.c
> =================================> --- linux.orig/kernel/irq/manage.c	2006-03-16 14:05:27.957927445 -0600
> +++ linux/kernel/irq/manage.c	2006-03-16 14:06:02.283661867 -0600
> @@ -201,6 +201,9 @@ int setup_irq(unsigned int irq, struct i
>  	 * The following block of code has to be executed atomically
>  	 */
>  	spin_lock_irqsave(&desc->lock,flags);
> +	if (new->flags & SA_PERCPU_IRQ) {
> +		desc->status |= IRQ_PER_CPU;
> +	}

looks good, although the braces aren't really needed for single-line
conditionals.

Re: [PATCH] Add SA_PERCPU_IRQ flag support

[Andrew Morton]

Dimitri Sivanich <sivanich@sgi.com> wrote:
>
> he generic request_irq/setup_irq code should support the SA_PERCPU_IRQ flag.
> 
> Not sure why it was left out, but this patch adds that support.
> 
> Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
> 
> Index: linux/kernel/irq/manage.c
> =================================> --- linux.orig/kernel/irq/manage.c	2006-03-16 14:05:27.957927445 -0600
> +++ linux/kernel/irq/manage.c	2006-03-16 14:06:02.283661867 -0600
> @@ -201,6 +201,9 @@ int setup_irq(unsigned int irq, struct i
>  	 * The following block of code has to be executed atomically
>  	 */
>  	spin_lock_irqsave(&desc->lock,flags);
> +	if (new->flags & SA_PERCPU_IRQ) {
> +		desc->status |= IRQ_PER_CPU;
> +	}
>  	p = &desc->action;
>  	if ((old = *p) != NULL) {
>  		/* Can't share interrupts unless both agree to */

Yes, we're presently going in and needlessly taking desc->lock on every
cpu-local interrupt.  However it only appears to affect mmtimer.c at
present.

Shouldn't we also have a check in there, to make sure that all the other
handlers off this IRQ agree about the per-cpuness of this interrupt?

Your patch broke the x86 build, btw..


From: Dimitri Sivanich <sivanich@sgi.com>

The generic request_irq/setup_irq code should support the SA_PERCPU_IRQ flag.

Also, check that all handlers agree to do per-cpu IRQs.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 kernel/irq/manage.c |   23 +++++++++++++++++++----
 1 files changed, 19 insertions(+), 4 deletions(-)

diff -puN kernel/irq/manage.c~generic-irq-add-sa_percpu_irq-flag-support kernel/irq/manage.c
--- 25/kernel/irq/manage.c~generic-irq-add-sa_percpu_irq-flag-support	Fri Mar 17 15:06:44 2006
+++ 25-akpm/kernel/irq/manage.c	Fri Mar 17 15:23:02 2006
@@ -204,10 +204,14 @@ int setup_irq(unsigned int irq, struct i
 	p = &desc->action;
 	if ((old = *p) != NULL) {
 		/* Can't share interrupts unless both agree to */
-		if (!(old->flags & new->flags & SA_SHIRQ)) {
-			spin_unlock_irqrestore(&desc->lock,flags);
-			return -EBUSY;
-		}
+		if (!(old->flags & new->flags & SA_SHIRQ))
+			goto mismatch;
+
+#ifdef ARCH_HAS_IRQ_PER_CPU
+		/* All handlers must agree on per-cpuness */
+		if ((old->flags & IRQ_PER_CPU) != (new->flags & IRQ_PER_CPU))
+			goto mismatch;
+#endif
 
 		/* add new interrupt at end of irq queue */
 		do {
@@ -219,6 +223,11 @@ int setup_irq(unsigned int irq, struct i
 
 	*p = new;
 
+#ifdef ARCH_HAS_IRQ_PER_CPU
+	if (new->flags & SA_PERCPU_IRQ)
+		desc->status |= IRQ_PER_CPU;
+#endif
+
 	if (!shared) {
 		desc->depth = 0;
 		desc->status &= ~(IRQ_DISABLED | IRQ_AUTODETECT |
@@ -236,6 +245,12 @@ int setup_irq(unsigned int irq, struct i
 	register_handler_proc(irq, new);
 
 	return 0;
+
+mismatch:
+	spin_unlock_irqrestore(&desc->lock, flags);
+	printk(KERN_ERR "%s: irq handler mismatch\n", __FUNCTION__);
+	dump_stack();
+	return -EBUSY;
 }
 
 #ifdef CONFIG_DEBUG_SHIRQ
_

Re: [PATCH] Add SA_PERCPU_IRQ flag support

[Andrew Morton]

Andrew Morton <akpm@osdl.org> wrote:
>
> +#ifdef ARCH_HAS_IRQ_PER_CPU
>  +	if (new->flags & SA_PERCPU_IRQ)
>  +		desc->status |= IRQ_PER_CPU;
>  +#endif

OK, five architectures define ARCH_HAS_IRQ_PER_CPU but only one of them
defines SA_PERCPU_IRQ.    Giving up.

Re: [PATCH] Add SA_PERCPU_IRQ flag support

[Dimitri Sivanich]

On Sat, Mar 18, 2006 at 01:49:00AM -0800, Andrew Morton wrote:
> Andrew Morton <akpm@osdl.org> wrote:
> >
> > +#ifdef ARCH_HAS_IRQ_PER_CPU
> >  +	if (new->flags & SA_PERCPU_IRQ)
> >  +		desc->status |= IRQ_PER_CPU;
> >  +#endif
> 
> OK, five architectures define ARCH_HAS_IRQ_PER_CPU but only one of them
> defines SA_PERCPU_IRQ.    Giving up.

Could we do the following (at least for now)?:

+#if defined(ARCH_HAS_IRQ_PER_CPU) && defined(SA_PERCPU_IRQ)
+	if (new->flags & SA_PERCPU_IRQ)
+		desc->status |= IRQ_PER_CPU;
+#endif

Re: [PATCH] Add SA_PERCPU_IRQ flag support

[Matthew Wilcox]

On Mon, Mar 20, 2006 at 08:17:47AM -0600, Dimitri Sivanich wrote:
> On Sat, Mar 18, 2006 at 01:49:00AM -0800, Andrew Morton wrote:
> > Andrew Morton <akpm@osdl.org> wrote:
> > >
> > > +#ifdef ARCH_HAS_IRQ_PER_CPU
> > >  +	if (new->flags & SA_PERCPU_IRQ)
> > >  +		desc->status |= IRQ_PER_CPU;
> > >  +#endif
> > 
> > OK, five architectures define ARCH_HAS_IRQ_PER_CPU but only one of them
> > defines SA_PERCPU_IRQ.    Giving up.
> 
> Could we do the following (at least for now)?:
> 
> +#if defined(ARCH_HAS_IRQ_PER_CPU) && defined(SA_PERCPU_IRQ)
> +	if (new->flags & SA_PERCPU_IRQ)
> +		desc->status |= IRQ_PER_CPU;
> +#endif

Why not just

#ifdef SA_PERCPU_IRQ
	if (new->flags & SA_PERCPU_IRQ)
		desc->status |= IRQ_PER_CPU;
#endif

Re: [PATCH] Add SA_PERCPU_IRQ flag support

[Dimitri Sivanich]

On Mon, Mar 20, 2006 at 07:22:07AM -0700, Matthew Wilcox wrote:
> On Mon, Mar 20, 2006 at 08:17:47AM -0600, Dimitri Sivanich wrote:
> > On Sat, Mar 18, 2006 at 01:49:00AM -0800, Andrew Morton wrote:
> > > Andrew Morton <akpm@osdl.org> wrote:
> > > >
> > > > +#ifdef ARCH_HAS_IRQ_PER_CPU
> > > >  +	if (new->flags & SA_PERCPU_IRQ)
> > > >  +		desc->status |= IRQ_PER_CPU;
> > > >  +#endif
> > > 
> > > OK, five architectures define ARCH_HAS_IRQ_PER_CPU but only one of them
> > > defines SA_PERCPU_IRQ.    Giving up.
> > 
> > Could we do the following (at least for now)?:
> > 
> > +#if defined(ARCH_HAS_IRQ_PER_CPU) && defined(SA_PERCPU_IRQ)
> > +	if (new->flags & SA_PERCPU_IRQ)
> > +		desc->status |= IRQ_PER_CPU;
> > +#endif
> 
> Why not just
> 
> #ifdef SA_PERCPU_IRQ
> 	if (new->flags & SA_PERCPU_IRQ)
> 		desc->status |= IRQ_PER_CPU;
> #endif

Fine with me. I was simply maintaining the ARCH_HAS_IRQ_PER_CPU convention.