dummy irq trace 'Flags mismatch'

dummy irq trace 'Flags mismatch'

[Dave Jones]

When set to built-in, the dummy irq driver causes this trace when I boot..

[    3.996055] genirq: Flags mismatch irq 0. 00000080 (dummy_irq) vs. 00015a20 (timer)
[    3.997055] Pid: 1, comm: swapper/0 Not tainted 3.9.0+ #29
[    3.997768] Call Trace:
[    3.998127]  [<ffffffff810f8635>] __setup_irq+0x515/0x550
[    3.998827]  [<ffffffff81f00e8c>] ? loop_init+0x150/0x150
[    3.999530]  [<ffffffff8146adf0>] ? transfer_xor+0x160/0x160
[    4.000259]  [<ffffffff810f8809>] request_threaded_irq+0xf9/0x1a0
[    4.001041]  [<ffffffff81f00e8c>] ? loop_init+0x150/0x150
[    4.001740]  [<ffffffff81f00eb8>] dummy_irq_init+0x2c/0x60
[    4.002450]  [<ffffffff810002e2>] do_one_initcall+0x122/0x170
[    4.003191]  [<ffffffff81ecef5c>] kernel_init_freeable+0x15b/0x1db
[    4.003978]  [<ffffffff81ece7da>] ? do_early_param+0x88/0x88
[    4.004710]  [<ffffffff816a87e0>] ? rest_init+0x140/0x140
[    4.005413]  [<ffffffff816a87ee>] kernel_init+0xe/0x180
[    4.006094]  [<ffffffff816ce91c>] ret_from_fork+0x7c/0xb0
[    4.006789]  [<ffffffff816a87e0>] ? rest_init+0x140/0x140
[    4.007561] dummy-irq: cannot register IRQ 0

Re: dummy irq trace 'Flags mismatch'

[Jiri Kosina]

On Mon, 29 Apr 2013, Dave Jones wrote:

> When set to built-in, the dummy irq driver causes this trace when I boot..
> 
> [    3.996055] genirq: Flags mismatch irq 0. 00000080 (dummy_irq) vs. 00015a20 (timer)
> [    3.997055] Pid: 1, comm: swapper/0 Not tainted 3.9.0+ #29
> [    3.997768] Call Trace:
> [    3.998127]  [<ffffffff810f8635>] __setup_irq+0x515/0x550
> [    3.998827]  [<ffffffff81f00e8c>] ? loop_init+0x150/0x150
> [    3.999530]  [<ffffffff8146adf0>] ? transfer_xor+0x160/0x160
> [    4.000259]  [<ffffffff810f8809>] request_threaded_irq+0xf9/0x1a0
> [    4.001041]  [<ffffffff81f00e8c>] ? loop_init+0x150/0x150
> [    4.001740]  [<ffffffff81f00eb8>] dummy_irq_init+0x2c/0x60
> [    4.002450]  [<ffffffff810002e2>] do_one_initcall+0x122/0x170
> [    4.003191]  [<ffffffff81ecef5c>] kernel_init_freeable+0x15b/0x1db
> [    4.003978]  [<ffffffff81ece7da>] ? do_early_param+0x88/0x88
> [    4.004710]  [<ffffffff816a87e0>] ? rest_init+0x140/0x140
> [    4.005413]  [<ffffffff816a87ee>] kernel_init+0xe/0x180
> [    4.006094]  [<ffffffff816ce91c>] ret_from_fork+0x7c/0xb0
> [    4.006789]  [<ffffffff816a87e0>] ? rest_init+0x140/0x140
> [    4.007561] dummy-irq: cannot register IRQ 0

Thanks for the report, Dave. That's actually kind of expected -- when one 
of the handlers on the IRQ line that is being debugged doesn't share IRQs, 
this is exactly what you want to get by the dummy-irq debugging facility.

In this case you haven't specified any IRQ# to the dummy-irq driver via 
kernel commandline, i.e. IRQ# is 0, and timer is not sharing IRQs, 
therefore dummy-irq debugging facility did its job, and you know that the 
IRQ can't be shared.

Not really sure whether this is something to fix. We could make dummy-irq 
a module-only thing, but that might be counter-productive in cases you 
really want to debug very early problems.

Or have it depend on CONFIG_EXPERT would probably make most sense ... ?

Thanks,

-- 
Jiri Kosina
SUSE Labs

Re: dummy irq trace 'Flags mismatch'

[Jonathan Corbet]

On Tue, 30 Apr 2013 06:59:22 +0200 (CEST)
Jiri Kosina <jkosina@suse.cz> wrote:

> Or have it depend on CONFIG_EXPERT would probably make most sense ... ?

We could also just have it tell you when you screwed up?  Something like
the following (compile tested only)?

jon
---
dummy-irq: require the user to specify an IRQ number

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/drivers/misc/dummy-irq.c b/drivers/misc/dummy-irq.c
index 7014167..c37eeed 100644
--- a/drivers/misc/dummy-irq.c
+++ b/drivers/misc/dummy-irq.c
@@ -19,7 +19,7 @@
 #include <linux/irq.h>
 #include <linux/interrupt.h>
 
-static int irq;
+static int irq = -1;
 
 static irqreturn_t dummy_interrupt(int irq, void *dev_id)
 {
@@ -36,6 +36,10 @@ static irqreturn_t dummy_interrupt(int irq, void *dev_id)
 
 static int __init dummy_irq_init(void)
 {
+	if (irq < 0) {
+		printk(KERN_ERR "dummy-irq: no IRQ given.  Use irq=N\n");
+		return -EIO;
+	}
 	if (request_irq(irq, &dummy_interrupt, IRQF_SHARED, "dummy_irq", &irq)) {
 		printk(KERN_ERR "dummy-irq: cannot register IRQ %d\n", irq);
 		return -EIO;

[PATCH] dummy-irq: require the user to specify an IRQ number

[Jiri Kosina]

From: Jonathan Corbet <corbet@lwn.net>
Subject: [PATCH] dummy-irq: require the user to specify an IRQ number

Make sure that we let the user know that without specifying IRQ#, 
dummy-irq driver is useless.

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/misc/dummy-irq.c b/drivers/misc/dummy-irq.c
index 7014167..c37eeed 100644
--- a/drivers/misc/dummy-irq.c
+++ b/drivers/misc/dummy-irq.c
@@ -19,7 +19,7 @@
 #include <linux/irq.h>
 #include <linux/interrupt.h>
 
-static int irq;
+static int irq = -1;
 
 static irqreturn_t dummy_interrupt(int irq, void *dev_id)
 {
@@ -36,6 +36,10 @@ static irqreturn_t dummy_interrupt(int irq, void *dev_id)
 
 static int __init dummy_irq_init(void)
 {
+	if (irq < 0) {
+		printk(KERN_ERR "dummy-irq: no IRQ given.  Use irq=N\n");
+		return -EIO;
+	}
 	if (request_irq(irq, &dummy_interrupt, IRQF_SHARED, "dummy_irq", &irq)) {
 		printk(KERN_ERR "dummy-irq: cannot register IRQ %d\n", irq);
 		return -EIO;
-- 
Jiri Kosina
SUSE Labs

Re: [PATCH] dummy-irq: require the user to specify an IRQ number

[Greg Kroah-Hartman]

On Tue, Apr 30, 2013 at 10:42:33PM +0200, Jiri Kosina wrote:
> From: Jonathan Corbet <corbet@lwn.net>
> Subject: [PATCH] dummy-irq: require the user to specify an IRQ number
> 
> Make sure that we let the user know that without specifying IRQ#, 
> dummy-irq driver is useless.
> 
> Reported-by: Dave Jones <davej@redhat.com>
> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Nice, I'll queue this up after 3.10-rc1 is out, thanks.

greg k-h

Re: [PATCH] dummy-irq: require the user to specify an IRQ number

[Jiri Kosina]

On Tue, 30 Apr 2013, Greg Kroah-Hartman wrote:

> > From: Jonathan Corbet <corbet@lwn.net>
> > Subject: [PATCH] dummy-irq: require the user to specify an IRQ number
> > 
> > Make sure that we let the user know that without specifying IRQ#, 
> > dummy-irq driver is useless.
> > 
> > Reported-by: Dave Jones <davej@redhat.com>
> > Signed-off-by: Jonathan Corbet <corbet@lwn.net>
> > Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> 
> Nice, I'll queue this up after 3.10-rc1 is out, thanks.

Thanks Greg.

Do you want me to resend this after rc1, or is it somewhere in your 
post-rc1 queue already?

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH] dummy-irq: require the user to specify an IRQ number

[Greg Kroah-Hartman]

On Tue, Apr 30, 2013 at 11:12:04PM +0200, Jiri Kosina wrote:
> On Tue, 30 Apr 2013, Greg Kroah-Hartman wrote:
> 
> > > From: Jonathan Corbet <corbet@lwn.net>
> > > Subject: [PATCH] dummy-irq: require the user to specify an IRQ number
> > > 
> > > Make sure that we let the user know that without specifying IRQ#, 
> > > dummy-irq driver is useless.
> > > 
> > > Reported-by: Dave Jones <davej@redhat.com>
> > > Signed-off-by: Jonathan Corbet <corbet@lwn.net>
> > > Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> > 
> > Nice, I'll queue this up after 3.10-rc1 is out, thanks.
> 
> Thanks Greg.
> 
> Do you want me to resend this after rc1, or is it somewhere in your 
> post-rc1 queue already?

It's in my queue already, no need for you to resend this.

thanks,

greg k-h