[PATCH] ARM : fix /proc/interrupts per online cpu

[PATCH] ARM : fix /proc/interrupts per online cpu

[Daniel Lezcano]

The loop should look at the online cpus instead of the present cpus
in order to hide the offline cpus in procfs like it is done on the
other architectures.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 arch/arm/kernel/smp.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index ef5640b..050f826 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -444,7 +444,7 @@ void show_ipi_list(struct seq_file *p, int prec)
 	for (i = 0; i < NR_IPI; i++) {
 		seq_printf(p, "%*s%u: ", prec - 1, "IPI", i);
 
-		for_each_present_cpu(cpu)
+		for_each_online_cpu(cpu)
 			seq_printf(p, "%10u ",
 				   __get_irq_stat(cpu, ipi_irqs[i]));
 
-- 
1.7.4.1

[PATCH] ARM : fix /proc/interrupts per online cpu

[Russell King - ARM Linux]

On Thu, Nov 24, 2011 at 05:05:19PM +0100, Daniel Lezcano wrote:
> The loop should look at the online cpus instead of the present cpus
> in order to hide the offline cpus in procfs like it is done on the
> other architectures.

And what happens if you're reading /proc/interrupts while a CPU is
changing state?

Given that it's just user presentation, whether its online or present
makes little odds - and having it as present CPUs makes the output
100% stable with the effects of hotplug.

[PATCH] ARM : fix /proc/interrupts per online cpu

[Daniel Lezcano]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 11/24/2011 09:21 PM, Russell King - ARM Linux wrote:
> On Thu, Nov 24, 2011 at 05:05:19PM +0100, Daniel Lezcano wrote:
>> The loop should look at the online cpus instead of the present cpus
>> in order to hide the offline cpus in procfs like it is done on the
>> other architectures.
> 
> And what happens if you're reading /proc/interrupts while a CPU is
> changing state?

> Given that it's just user presentation, whether its online or present
> makes little odds - and having it as present CPUs makes the output
> 100% stable with the effects of hotplug.

IMO, there is no problem to read /proc/interrupts while a CPU is
changing its state. In the worst case, we will show an obsolete
information to the userspace. The same happens when we do 'ps', we have
no guarantee a process still exists when the information is displayed.
But I may be wrong and in this case, the other arch have a bug.

The procfs is used as an API from the userspace and AFAICS the other
architectures display their arch specific interrupts for the online
cpus, not the present cpus.

Other non-arch dependant informations are per online cpus, so while
looking at the /proc/interrupts we have column shift for the IPI on ARM.

I don't know if it is worth to fix that but that may be more consistent.

Thanks

  -- Daniel



./sparc/kernel/irq_64.c:int arch_show_interrupts(struct seq_file *p, int
prec)
./sparc/kernel/irq_64.c-{
./sparc/kernel/irq_64.c-	int j;
./sparc/kernel/irq_64.c-
./sparc/kernel/irq_64.c-	seq_printf(p, "NMI: ");
./sparc/kernel/irq_64.c-	for_each_online_cpu(j)
./sparc/kernel/irq_64.c-		seq_printf(p, "%10u ", cpu_data(j).__nmi_count);
./sparc/kernel/irq_64.c-	seq_printf(p, "     Non-maskable interrupts\n");
./sparc/kernel/irq_64.c-	return 0;
./sparc/kernel/irq_64.c-}

- -----------------------------------------------------------------------

./sparc/kernel/irq_32.c:int arch_show_interrupts(struct seq_file *p, int
prec)
./sparc/kernel/irq_32.c-{
./sparc/kernel/irq_32.c-	int j;
./sparc/kernel/irq_32.c-
./sparc/kernel/irq_32.c-#ifdef CONFIG_SMP
./sparc/kernel/irq_32.c-	seq_printf(p, "RES: ");
./sparc/kernel/irq_32.c-	for_each_online_cpu(j)
./sparc/kernel/irq_32.c-		seq_printf(p, "%10u ",
cpu_data(j).irq_resched_count);
./sparc/kernel/irq_32.c-	seq_printf(p, "     IPI rescheduling
interrupts\n");
./sparc/kernel/irq_32.c-	seq_printf(p, "CAL: ");
./sparc/kernel/irq_32.c-	for_each_online_cpu(j)

- -----------------------------------------------------------------------

./powerpc/kernel/irq.c:int arch_show_interrupts(struct seq_file *p, int
prec)
./powerpc/kernel/irq.c-{
./powerpc/kernel/irq.c-	int j;
./powerpc/kernel/irq.c-
./powerpc/kernel/irq.c-#if defined(CONFIG_PPC32) && defined(CONFIG_TAU_INT)
./powerpc/kernel/irq.c-	if (tau_initialized) {
./powerpc/kernel/irq.c-		seq_printf(p, "%*s: ", prec, "TAU");
./powerpc/kernel/irq.c-		for_each_online_cpu(j)
./powerpc/kernel/irq.c-			seq_printf(p, "%10u ", tau_interrupts(j));
./powerpc/kernel/irq.c-		seq_puts(p, "  PowerPC             Thermal
Assist (cpu temp)\n");
./powerpc/kernel/irq.c-	}

- ------------------------------------------------------------------------

./x86/kernel/irq.c:int arch_show_interrupts(struct seq_file *p, int prec)
./x86/kernel/irq.c-{
./x86/kernel/irq.c-	int j;
./x86/kernel/irq.c-
./x86/kernel/irq.c-	seq_printf(p, "%*s: ", prec, "NMI");
./x86/kernel/irq.c-	for_each_online_cpu(j)
./x86/kernel/irq.c-		seq_printf(p, "%10u ", irq_stats(j)->__nmi_count);
./x86/kernel/irq.c-	seq_printf(p, "  Non-maskable interrupts\n");
./x86/kernel/irq.c-#ifdef CONFIG_X86_LOCAL_APIC
./x86/kernel/irq.c-	seq_printf(p, "%*s: ", prec, "LOC");
./x86/kernel/irq.c-	for_each_online_cpu(j)

- ------------------------------------------------------------------------

./mn10300/kernel/irq.c:int arch_show_interrupts(struct seq_file *p, int
prec)
./mn10300/kernel/irq.c-{
./mn10300/kernel/irq.c-#ifdef CONFIG_MN10300_WD_TIMER
./mn10300/kernel/irq.c-	int j;
./mn10300/kernel/irq.c-
./mn10300/kernel/irq.c-	seq_printf(p, "%*s: ", prec, "NMI");
./mn10300/kernel/irq.c-	for (j = 0; j < NR_CPUS; j++)
./mn10300/kernel/irq.c-		if (cpu_online(j))
./mn10300/kernel/irq.c-			seq_printf(p, "%10u ", nmi_count(j));
./mn10300/kernel/irq.c-	seq_putc(p, '\n');
./mn10300/kernel/irq.c-#endif

- ------------------------------------------------------------------------

./alpha/kernel/irq.c:int arch_show_interrupts(struct seq_file *p, int prec)
./alpha/kernel/irq.c-{
./alpha/kernel/irq.c-	int j;
./alpha/kernel/irq.c-
./alpha/kernel/irq.c-#ifdef CONFIG_SMP
./alpha/kernel/irq.c-	seq_puts(p, "IPI: ");
./alpha/kernel/irq.c-	for_each_online_cpu(j)
./alpha/kernel/irq.c-		seq_printf(p, "%10lu ", cpu_data[j].ipi_count);
./alpha/kernel/irq.c-	seq_putc(p, '\n');
./alpha/kernel/irq.c-#endif
./alpha/kernel/irq.c-	seq_puts(p, "PMI: ");

- ------------------------------------------------------------------------

./sh/kernel/irq.c:int arch_show_interrupts(struct seq_file *p, int prec)
./sh/kernel/irq.c-{
./sh/kernel/irq.c-	int j;
./sh/kernel/irq.c-
./sh/kernel/irq.c-	seq_printf(p, "%*s: ", prec, "NMI");
./sh/kernel/irq.c-	for_each_online_cpu(j)
./sh/kernel/irq.c-		seq_printf(p, "%10u ", irq_stat[j].__nmi_count);
./sh/kernel/irq.c-	seq_printf(p, "  Non-maskable interrupts\n");
./sh/kernel/irq.c-
./sh/kernel/irq.c-	seq_printf(p, "%*s: %10u\n", prec, "ERR",
atomic_read(&irq_err_count));
./sh/kernel/irq.c-



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