Re: [PATCH] powerpc/mpic: Disable preemption when calling mpic_processor_id()
On Sep 26, 2013, at 7:18 PM, Scott Wood wrote:
Otherwise, we get a debug traceback due to the use of
smp_processor_id() (or get_paca()) inside hard_smp_processor_id().
mpic_host_map() is just looking for a default CPU, so it doesn't matter
if we migrate after getting the CPU ID.
Signed-off-by: Scott Wood scottw...@freescale.com
---
arch/powerpc/sysdev/mpic.c | 8 +++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 1be54fa..bdcb858 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1088,8 +1088,14 @@ static int mpic_host_map(struct irq_domain *h,
unsigned int virq,
* is done here.
*/
if (!mpic_is_ipi(mpic, hw) (mpic-flags MPIC_NO_RESET)) {
+ int cpu;
+
+ preempt_disable();
+ cpu = mpic_processor_id(mpic);
+ preempt_enable();
+
Any reason you didn't stick this inside of mpic_processor_id() ?
mpic_set_vector(virq, hw);
- mpic_set_destination(virq, mpic_processor_id(mpic));
+ mpic_set_destination(virq, cpu);
mpic_irq_set_priority(virq, 8);
}
--
1.8.1.2
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Re: [PATCH] powerpc/mpic: Disable preemption when calling mpic_processor_id()
On Fri, 2013-09-27 at 10:52 -0500, Kumar Gala wrote:
On Sep 26, 2013, at 7:18 PM, Scott Wood wrote:
Otherwise, we get a debug traceback due to the use of
smp_processor_id() (or get_paca()) inside hard_smp_processor_id().
mpic_host_map() is just looking for a default CPU, so it doesn't matter
if we migrate after getting the CPU ID.
Signed-off-by: Scott Wood scottw...@freescale.com
---
arch/powerpc/sysdev/mpic.c | 8 +++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 1be54fa..bdcb858 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1088,8 +1088,14 @@ static int mpic_host_map(struct irq_domain *h,
unsigned int virq,
* is done here.
*/
if (!mpic_is_ipi(mpic, hw) (mpic-flags MPIC_NO_RESET)) {
+ int cpu;
+
+ preempt_disable();
+ cpu = mpic_processor_id(mpic);
+ preempt_enable();
+
Any reason you didn't stick this inside of mpic_processor_id() ?
Because the debug check might be valid for other callers and we don't
want to defeat it. In this caller it's used only as a heuristic and
thus it doesn't matter if we re-enable preemption before using the
result.
-Scott
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Re: [PATCH] powerpc/mpic: Disable preemption when calling mpic_processor_id()
On Sep 27, 2013, at 11:15 AM, Scott Wood wrote:
On Fri, 2013-09-27 at 10:52 -0500, Kumar Gala wrote:
On Sep 26, 2013, at 7:18 PM, Scott Wood wrote:
Otherwise, we get a debug traceback due to the use of
smp_processor_id() (or get_paca()) inside hard_smp_processor_id().
mpic_host_map() is just looking for a default CPU, so it doesn't matter
if we migrate after getting the CPU ID.
Signed-off-by: Scott Wood scottw...@freescale.com
---
arch/powerpc/sysdev/mpic.c | 8 +++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 1be54fa..bdcb858 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1088,8 +1088,14 @@ static int mpic_host_map(struct irq_domain *h,
unsigned int virq,
* is done here.
*/
if (!mpic_is_ipi(mpic, hw) (mpic-flags MPIC_NO_RESET)) {
+ int cpu;
+
+ preempt_disable();
+ cpu = mpic_processor_id(mpic);
+ preempt_enable();
+
Any reason you didn't stick this inside of mpic_processor_id() ?
Because the debug check might be valid for other callers and we don't
want to defeat it. In this caller it's used only as a heuristic and
thus it doesn't matter if we re-enable preemption before using the
result.
Gotcha, I think you should reword the commit message. Reading it makes me
think that preemption should be disabled for all mpic_processor_id() calls.
- k
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Re: [PATCH] powerpc/mpic: Disable preemption when calling mpic_processor_id()
On Fri, 2013-09-27 at 12:09 -0500, Kumar Gala wrote:
On Sep 27, 2013, at 11:15 AM, Scott Wood wrote:
On Fri, 2013-09-27 at 10:52 -0500, Kumar Gala wrote:
On Sep 26, 2013, at 7:18 PM, Scott Wood wrote:
Otherwise, we get a debug traceback due to the use of
smp_processor_id() (or get_paca()) inside hard_smp_processor_id().
mpic_host_map() is just looking for a default CPU, so it doesn't matter
if we migrate after getting the CPU ID.
Signed-off-by: Scott Wood scottw...@freescale.com
---
arch/powerpc/sysdev/mpic.c | 8 +++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 1be54fa..bdcb858 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1088,8 +1088,14 @@ static int mpic_host_map(struct irq_domain *h,
unsigned int virq,
* is done here.
*/
if (!mpic_is_ipi(mpic, hw) (mpic-flags MPIC_NO_RESET)) {
+ int cpu;
+
+ preempt_disable();
+ cpu = mpic_processor_id(mpic);
+ preempt_enable();
+
Any reason you didn't stick this inside of mpic_processor_id() ?
Because the debug check might be valid for other callers and we don't
want to defeat it. In this caller it's used only as a heuristic and
thus it doesn't matter if we re-enable preemption before using the
result.
Gotcha, I think you should reword the commit message. Reading it makes
me think that preemption should be disabled for all mpic_processor_id()
calls.
It should be disabled for all mpic_processor_id() calls -- but some
calls will need preemption to be disabled for longer than just the call
to mpic_processor_id().
I did mention in the commit message why mpic_host_map() is unusual.
BTW, I wonder why we don't use mpic_set_affinity (and thus
irq_choose_cpu), both here and in the non-MPIC_NO_RESET case. Though I
usually notice IRQs being round robinned -- I guess userspace is writing
to the affinity in proc? Or is something elsewhere in the kernel
calling set_affinity at some point?
Another thing I just noticed while looking at IRQ_DESTINATION-related
code, in mpic_teardown_this_cpu(), what stops it from removing the only
CPU that an interrupt is targeted at?
-Scott
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[PATCH] powerpc/mpic: Disable preemption when calling mpic_processor_id()
Otherwise, we get a debug traceback due to the use of
smp_processor_id() (or get_paca()) inside hard_smp_processor_id().
mpic_host_map() is just looking for a default CPU, so it doesn't matter
if we migrate after getting the CPU ID.
Signed-off-by: Scott Wood scottw...@freescale.com
---
arch/powerpc/sysdev/mpic.c | 8 +++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 1be54fa..bdcb858 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1088,8 +1088,14 @@ static int mpic_host_map(struct irq_domain *h, unsigned
int virq,
* is done here.
*/
if (!mpic_is_ipi(mpic, hw) (mpic-flags MPIC_NO_RESET)) {
+ int cpu;
+
+ preempt_disable();
+ cpu = mpic_processor_id(mpic);
+ preempt_enable();
+
mpic_set_vector(virq, hw);
- mpic_set_destination(virq, mpic_processor_id(mpic));
+ mpic_set_destination(virq, cpu);
mpic_irq_set_priority(virq, 8);
}
--
1.8.1.2
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