linux-kernel - [PATCH] i386/x86_64: NMI watchdog: Protect smp_call_function() within CONFIG

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Message-ID: <a781481a0706070407x59c78190n65d9303857feee9c@mail.gmail.com>
Date:	Thu, 7 Jun 2007 16:37:32 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Cc:	"Ingo Molnar" <mingo@...hat.com>,
	"Andi Kleen" <andi@...stfloor.org>, "Alan Cox" <alan@...hat.com>
Subject: [PATCH] i386/x86_64: NMI watchdog: Protect smp_call_function() within CONFIG_SMP and some trivialities

a. arch/i386/kernel/nmi.c:check_nmi_watchdog() calls
   smp_call_function() unconditionally. Protect it inside
   a #ifdef CONFIG_SMP, as it is meaningless for UP, also
   making i386's version similar to x86_64's.
b. Also update the filename in the comment on top of
   arch/{i386, x86_64}/kernel/nmi.c, while we're editing
   these files.

BTW: smp_call_function() simply returns 0 and
smp_call_function_single() simply returns -EBUSY when !SMP.
These appear to be just some ad hoc values. IMHO, we should
be going BUG() in both these cases because "other" CPUs for
!SMP are undefined / meaningless. [ Copying Alan Cox. ]

Signed-off-by: Satyam Sharma <ssatyam@....iitk.ac.in>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Andi Kleen <ak@...e.de>
Cc: Alan Cox <alan@...hat.com>

---

 arch/i386/kernel/nmi.c   |    4 +++-
 arch/x86_64/kernel/nmi.c |    2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

---

diff -ruNp a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
--- a/arch/i386/kernel/nmi.c	2007-06-07 12:46:34.000000000 +0530
+++ b/arch/i386/kernel/nmi.c	2007-06-07 15:43:52.000000000 +0530
@@ -1,5 +1,5 @@
 /*
- *  linux/arch/i386/nmi.c
+ *  linux/arch/i386/kernel/nmi.c
  *
  *  NMI watchdog support on APIC systems
  *
@@ -89,8 +89,10 @@ static int __init check_nmi_watchdog(voi

 	printk(KERN_INFO "Testing NMI watchdog ... ");

+#ifdef CONFIG_SMP
 	if (nmi_watchdog == NMI_LOCAL_APIC)
 		smp_call_function(nmi_cpu_busy, (void *)&endflag, 0, 0);
+#endif

 	for_each_possible_cpu(cpu)
 		prev_nmi_count[cpu] = per_cpu(irq_stat, cpu).__nmi_count;
diff -ruNp a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
--- a/arch/x86_64/kernel/nmi.c	2007-06-07 12:46:39.000000000 +0530
+++ b/arch/x86_64/kernel/nmi.c	2007-06-07 15:43:13.000000000 +0530
@@ -1,5 +1,5 @@
 /*
- *  linux/arch/x86_64/nmi.c
+ *  linux/arch/x86_64/kernel/nmi.c
  *
  *  NMI watchdog support on APIC systems
  *
-
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