[PATCH] check nmi watchdog is broken

A bug against an xSeries system showed up recently noting that the
check_nmi_watchdog() test was failing.

I have been investigating it and discovered in both i386 and x86_64 the
recent change to the routine to use the cpu_callin_map has uncovered a
problem.  Prior to that change, on an SMP box, the test was trivally
passing because all cpu's were found to not yet be online, but now with the
callin_map they are discovered, it goes on to test the counter and they
have not yet begun to increment, so it announces a CPU is stuck and bails
out.

On all the systems I have access to test, the announcement of failure is
also bougs...  by the time you can login and check /proc/interrupts, the
NMI count is happily incrementing on all CPUs.  Its just that the test is
being done too early.

I have tried moving the call to the test around a bit, and it was always
too early.  I finally hit on this proposed solution, it delays the routine
via a late_initcall(), seems like the right solution to me.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 7 insertions, 4 deletions

diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index 29a257295484..60be58617eb9 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -1607,7 +1607,6 @@ static inline void check_timer(void)
                                 disable_8259A_irq(0);
                                 setup_nmi();
                                 enable_8259A_irq(0);
-                                check_nmi_watchdog();
                         }
                         return;
                 }
@@ -1627,7 +1626,6 @@ static inline void check_timer(void)
                         nmi_watchdog_default();
                         if (nmi_watchdog == NMI_IO_APIC) {
                                 setup_nmi();
-                                check_nmi_watchdog();
                         }
                         return;
                 }
diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index e00d4adec36b..61de0b34a01e 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -112,17 +112,20 @@ static __init int cpu_has_lapic(void)
         }       
 }
 
-int __init check_nmi_watchdog (void)
+static int __init check_nmi_watchdog (void)
 {
         int counts[NR_CPUS];
         int cpu;
 
+        if (nmi_watchdog == NMI_NONE)
+                return 0;
+
         if (nmi_watchdog == NMI_LOCAL_APIC && !cpu_has_lapic())  {
                 nmi_watchdog = NMI_NONE;
                 return -1; 
         }       
 
-        printk(KERN_INFO "testing NMI watchdog ... ");
+        printk(KERN_INFO "Testing NMI watchdog ... ");
 
         for (cpu = 0; cpu < NR_CPUS; cpu++)
                 counts[cpu] = cpu_pda[cpu].__nmi_count; 
@@ -148,6 +151,8 @@ int __init check_nmi_watchdog (void)
 
         return 0;
 }
+/* Have this called later during boot so counters are updating */
+late_initcall(check_nmi_watchdog);
 
 int __init setup_nmi_watchdog(char *str)
 {