linux-kernel - Re: [tip:perf/urgent] perf, x86: Fix accidentally ack'ing a second event on intel perf counter

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Message-ID: <20100903183559.GB4879@redhat.com>
Date:	Fri, 3 Sep 2010 14:35:59 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, hpa@...or.com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/urgent] perf, x86: Fix accidentally ack'ing a second
 event on intel perf counter

On Fri, Sep 03, 2010 at 10:15:16AM -0700, Yinghai Lu wrote:
> On 09/03/2010 08:00 AM, Don Zickus wrote:
> > On Fri, Sep 03, 2010 at 12:39:25AM -0700, Yinghai Lu wrote:
> >> Can you put this into perf branch ?
> >>
> >> Thanks
> >>
> >> Yinghai
> >>
> >> [PATCH] x86,nmi: move unknown_nmi_panic to traps.c
> > 
> > This patch duplicates a bunch of stuff we already have in
> > unknown_nmi_error.  The only thing I think you are interested in is using
> > the 'unknown_nmi_panic' flag.  I am putting together a smaller patch that
> > uses that flag in traps.c (though it would be nice to combine that flag
> > with panic_on_unrecovered_nmi).
> 
> please make sure
> keep using unknown_nmi_panic in boot command line and  sysctl
> when LOCKUP_DETECTOR is defined.
> 
> that does work until hw nmi watchdog is merged with software lock detector.
> assume that time hw nmi watchdog is relying on perf nmi and perf nmi would eat all unknown nmi.
> good to have Robert/Peter/Don's patches to make per nmi not to eat all unknown nmi.

Hi Yinghai,

Here is the simpler patch I came up with.  It piggy backs off the
unknown_nmi_error code already available.  I compile it with the old and
new nmi watchdog and tested it with sysctl and the kernel parameter.
Everything seems to panic properly.

Let me know if this meets your needs.

Cheers,
Don

diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c
index cefd694..e66b16d 100644
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -100,7 +100,6 @@ void acpi_nmi_disable(void) { return; }
 #endif
 atomic_t nmi_active = ATOMIC_INIT(0);           /* oprofile uses this */
 EXPORT_SYMBOL(nmi_active);
-int unknown_nmi_panic;
 void cpu_nmi_set_wd_enabled(void) { return; }
 void stop_apic_nmi_watchdog(void *unused) { return; }
 void setup_apic_nmi_watchdog(void *unused) { return; }
diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index a43f71c..dc35af4 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -37,7 +37,6 @@
 
 #include <asm/mach_traps.h>
 
-int unknown_nmi_panic;
 int nmi_watchdog_enabled;
 
 /* For reliability, we're prepared to waste bits here. */
@@ -483,13 +482,6 @@ static void disable_ioapic_nmi_watchdog(void)
 	on_each_cpu(stop_apic_nmi_watchdog, NULL, 1);
 }
 
-static int __init setup_unknown_nmi_panic(char *str)
-{
-	unknown_nmi_panic = 1;
-	return 1;
-}
-__setup("unknown_nmi_panic", setup_unknown_nmi_panic);
-
 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
 {
 	unsigned char reason = get_nmi_reason();
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 60788de..095eea8 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -300,6 +300,16 @@ gp_in_kernel:
 	die("general protection fault", regs, error_code);
 }
 
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_X86_LOCAL_APIC)
+int unknown_nmi_panic;
+static int __init setup_unknown_nmi_panic(char *str)
+{
+	unknown_nmi_panic = 1;
+	return 1;
+}
+__setup("unknown_nmi_panic", setup_unknown_nmi_panic);
+#endif
+
 static notrace __kprobes void
 mem_parity_error(unsigned char reason, struct pt_regs *regs)
 {
@@ -371,6 +381,10 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 			reason, smp_processor_id());
 
 	printk(KERN_EMERG "Do you have a strange power saving mode enabled?\n");
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_X86_LOCAL_APIC)
+	if (unknown_nmi_panic)
+		die_nmi("", regs, 1);
+#endif
 	if (panic_on_unrecovered_nmi)
 		panic("NMI: Not continuing");
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index ca38e8e..71516a4 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -739,7 +739,7 @@ static struct ctl_table kern_table[] = {
 		.extra2		= &one,
 	},
 #endif
-#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86) && !defined(CONFIG_LOCKUP_DETECTOR)
+#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
 	{
 		.procname       = "unknown_nmi_panic",
 		.data           = &unknown_nmi_panic,
@@ -747,6 +747,8 @@ static struct ctl_table kern_table[] = {
 		.mode           = 0644,
 		.proc_handler   = proc_dointvec,
 	},
+#endif
+#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86) && !defined(CONFIG_LOCKUP_DETECTOR)
 	{
 		.procname       = "nmi_watchdog",
 		.data           = &nmi_watchdog_enabled,
--
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