linux-kernel - [tip:x86/urgent] x86: avoid theoretical spurious NMI backtraces with CONFIG_CPUMASK

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Message-ID: <tip-fcc5c4a2feea3886dc058498b28508b2731720d5@git.kernel.org>
Date:	Tue, 21 Apr 2009 08:12:42 GMT
From:	tip-bot for Rusty Russell <rusty@...tcorp.com.au>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	rostedt@...dmis.org, rusty@...tcorp.com.au, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:x86/urgent] x86: avoid theoretical spurious NMI backtraces with CONFIG_CPUMASK_OFFSTACK=y

Commit-ID:  fcc5c4a2feea3886dc058498b28508b2731720d5
Gitweb:     http://git.kernel.org/tip/fcc5c4a2feea3886dc058498b28508b2731720d5
Author:     Rusty Russell <rusty@...tcorp.com.au>
AuthorDate: Tue, 21 Apr 2009 16:03:41 +0930
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 21 Apr 2009 10:09:50 +0200

x86: avoid theoretical spurious NMI backtraces with CONFIG_CPUMASK_OFFSTACK=y

In theory (though not shown in practice) alloc_cpumask_var() doesn't zero
memory, so CPUs might print an "NMI backtrace for cpu %d" once on boot.

(Bug introduced in fcef8576d8a64fc603e719c97d423f9f6d4e0e8b).

[ Impact: avoid theoretical syslog noise in rare configs ]

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Cc: Steven Rostedt <rostedt@...dmis.org>
LKML-Reference: <alpine.DEB.2.00.0904202113520.10097@...dalf.stny.rr.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 arch/x86/kernel/apic/nmi.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c
index 2ba52f3..ce4fbfa 100644
--- a/arch/x86/kernel/apic/nmi.c
+++ b/arch/x86/kernel/apic/nmi.c
@@ -138,7 +138,7 @@ int __init check_nmi_watchdog(void)
 	if (!prev_nmi_count)
 		goto error;
 
-	alloc_cpumask_var(&backtrace_mask, GFP_KERNEL);
+	alloc_cpumask_var(&backtrace_mask, GFP_KERNEL|__GFP_ZERO);
 	printk(KERN_INFO "Testing NMI watchdog ... ");
 
 #ifdef CONFIG_SMP
--
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