linux-kernel - [PATCH 1/2] Always probe the NMI watchdog

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Date:	Wed, 20 Jun 2007 20:34:48 +0200
From:	Björn Steinbrink <B.Steinbrink@....de>
To:	Andi Kleen <ak@...e.de>, eranian@....hp.com, mingo@...e.hu,
	linux-kernel@...r.kernel.org, levon@...ementarian.org,
	perfmon@...ali.hpl.hp.com, oprofile-list@...ts.sourceforge.net,
	wcohen@...hat.com, akpm@...ux-foundation.org
Subject: [PATCH 1/2] Always probe the NMI watchdog

The performance counter allocator relies on the nmi watchdog being
probed, so we have to do that even if the watchdog is not enabled.

Signed-off-by: Björn Steinbrink <B.Steinbrink@....de>
---
 arch/i386/kernel/cpu/perfctr-watchdog.c |   11 +++++------
 arch/i386/kernel/nmi.c                  |    3 +++
 arch/x86_64/kernel/nmi.c                |    3 +++
 include/asm-i386/nmi.h                  |    1 +
 include/asm-x86_64/nmi.h                |    1 +
 5 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/i386/kernel/cpu/perfctr-watchdog.c b/arch/i386/kernel/cpu/perfctr-watchdog.c
index f0b6763..a12dbcf 100644
--- a/arch/i386/kernel/cpu/perfctr-watchdog.c
+++ b/arch/i386/kernel/cpu/perfctr-watchdog.c
@@ -572,7 +572,7 @@ static struct wd_ops intel_arch_wd_ops = {
 	.evntsel = MSR_ARCH_PERFMON_EVENTSEL0,
 };
 
-static void probe_nmi_watchdog(void)
+void probe_nmi_watchdog(void)
 {
 	switch (boot_cpu_data.x86_vendor) {
 	case X86_VENDOR_AMD:
@@ -610,17 +610,16 @@ static void probe_nmi_watchdog(void)
 
 int lapic_watchdog_init(unsigned nmi_hz)
 {
-	if (!wd_ops) {
-		probe_nmi_watchdog();
-		if (!wd_ops)
-			return -1;
+	if (!wd_ops)
+		return -1;
 
+	/* hack to make sure that we only try to reserver the perfctrs once */
+	if (smp_processor_id() == 0)
 		if (!wd_ops->reserve()) {
 			printk(KERN_ERR
 				"NMI watchdog: cannot reserve perfctrs\n");
 			return -1;
 		}
-	}
 
 	if (!(wd_ops->setup(nmi_hz))) {
 		printk(KERN_ERR "Cannot setup NMI watchdog on CPU %d\n",
diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index fba121f..8788f91 100644
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -248,6 +248,9 @@ void setup_apic_nmi_watchdog (void *unused)
 	if ((smp_processor_id() != 0) && (atomic_read(&nmi_active) <= 0))
 		return;
 
+	/* always probe the watchdog, the perfctr allocator requires that */
+	probe_nmi_watchdog();
+
 	switch (nmi_watchdog) {
 	case NMI_LOCAL_APIC:
 		__get_cpu_var(wd_enabled) = 1; /* enable it before to avoid race with handler */
diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index 931c64b..3229a26 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -255,6 +255,9 @@ void setup_apic_nmi_watchdog(void *unused)
 	if ((smp_processor_id() != 0) && (atomic_read(&nmi_active) <= 0))
 		return;
 
+	/* always probe the watchdog, the perfctr allocator requires that */
+	probe_nmi_watchdog();
+
 	switch (nmi_watchdog) {
 	case NMI_LOCAL_APIC:
 		__get_cpu_var(wd_enabled) = 1;
diff --git a/include/asm-i386/nmi.h b/include/asm-i386/nmi.h
index fb1e133..cf87cd0 100644
--- a/include/asm-i386/nmi.h
+++ b/include/asm-i386/nmi.h
@@ -18,6 +18,7 @@
 int do_nmi_callback(struct pt_regs *regs, int cpu);
 
 extern int nmi_watchdog_enabled;
+extern void probe_nmi_watchdog(void);
 extern int avail_to_resrv_perfctr_nmi_bit(unsigned int);
 extern int avail_to_resrv_perfctr_nmi(unsigned int);
 extern int reserve_perfctr_nmi(unsigned int);
diff --git a/include/asm-x86_64/nmi.h b/include/asm-x86_64/nmi.h
index d0a7f53..f61653b 100644
--- a/include/asm-x86_64/nmi.h
+++ b/include/asm-x86_64/nmi.h
@@ -45,6 +45,7 @@ extern int panic_on_timeout;
 extern int unknown_nmi_panic;
 extern int nmi_watchdog_enabled;
 
+extern void probe_nmi_watchdog(void);
 extern int check_nmi_watchdog(void);
 extern int avail_to_resrv_perfctr_nmi_bit(unsigned int);
 extern int avail_to_resrv_perfctr_nmi(unsigned int);
-- 
1.5.2.2

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