x86, apic: Limit apic dumping, introduce new show_lapic= setup option

In case if a system has a large number of cpus printing apics
contents may consume a long time period.

We limit such an output by 1 apic by default. But to have an
ability to see all apics or some part of them we introduce
"show_lapic" setup option which allow us to limit/unlimit the
number of APICs being dumped.

Example: apic=debug show_lapic=5, or apic=debug show_lapic=all

Also move apic_verbosity checking upper that way so helper routines
do not need to inspect it at all.

Suggested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: yinghai@kernel.org
Cc: macro@linux-mips.org
LKML-Reference: <20091013201022.926793122@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 32 insertions, 15 deletions

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index dc69f28489f5..8c718c93d079 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1599,9 +1599,6 @@ __apicdebuginit(void) print_IO_APIC(void)
         struct irq_desc *desc;
         unsigned int irq;
 
-        if (apic_verbosity == APIC_QUIET)
-                return;
-
         printk(KERN_DEBUG "number of MP IRQ sources: %d.\n", mp_irq_entries);
         for (i = 0; i < nr_ioapics; i++)
                 printk(KERN_DEBUG "number of IO-APIC #%d registers: %d.\n",
@@ -1708,9 +1705,6 @@ __apicdebuginit(void) print_APIC_field(int base)
 {
         int i;
 
-        if (apic_verbosity == APIC_QUIET)
-                return;
-
         printk(KERN_DEBUG);
 
         for (i = 0; i < 8; i++)
@@ -1724,9 +1718,6 @@ __apicdebuginit(void) print_local_APIC(void *dummy)
         unsigned int i, v, ver, maxlvt;
         u64 icr;
 
-        if (apic_verbosity == APIC_QUIET)
-                return;
-
         printk(KERN_DEBUG "printing local APIC contents on CPU#%d/%d:\n",
                 smp_processor_id(), hard_smp_processor_id());
         v = apic_read(APIC_ID);
@@ -1824,13 +1815,19 @@ __apicdebuginit(void) print_local_APIC(void *dummy)
         printk("\n");
 }
 
-__apicdebuginit(void) print_all_local_APICs(void)
+__apicdebuginit(void) print_local_APICs(int maxcpu)
 {
         int cpu;
 
+        if (!maxcpu)
+                return;
+
         preempt_disable();
-        for_each_online_cpu(cpu)
+        for_each_online_cpu(cpu) {
+                if (cpu >= maxcpu)
+                        break;
                 smp_call_function_single(cpu, print_local_APIC, NULL, 1);
+        }
         preempt_enable();
 }
 
@@ -1839,7 +1836,7 @@ __apicdebuginit(void) print_PIC(void)
         unsigned int v;
         unsigned long flags;
 
-        if (apic_verbosity == APIC_QUIET || !nr_legacy_irqs)
+        if (!nr_legacy_irqs)
                 return;
 
         printk(KERN_DEBUG "\nprinting PIC contents\n");
@@ -1866,21 +1863,41 @@ __apicdebuginit(void) print_PIC(void)
         printk(KERN_DEBUG "... PIC ELCR: %04x\n", v);
 }
 
-__apicdebuginit(int) print_all_ICs(void)
+static int __initdata show_lapic = 1;
+static __init int setup_show_lapic(char *arg)
+{
+        int num = -1;
+
+        if (strcmp(arg, "all") == 0) {
+                show_lapic = CONFIG_NR_CPUS;
+        } else {
+                get_option(&arg, &num);
+                if (num >= 0)
+                        show_lapic = num;
+        }
+
+        return 1;
+}
+__setup("show_lapic=", setup_show_lapic);
+
+__apicdebuginit(int) print_ICs(void)
 {
+        if (apic_verbosity == APIC_QUIET)
+                return 0;
+
         print_PIC();
 
         /* don't print out if apic is not there */
         if (!cpu_has_apic && !apic_from_smp_config())
                 return 0;
 
-        print_all_local_APICs();
+        print_local_APICs(show_lapic);
         print_IO_APIC();
 
         return 0;
 }
 
-fs_initcall(print_all_ICs);
+fs_initcall(print_ICs);
 
 
 /* Where if anywhere is the i8259 connect in external int mode */