From 2f537a9f8e82f55c241b002c8cfbf34303b45ada Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Tue, 21 Apr 2009 16:00:15 +0930 Subject: x86: fix boot crash in NMI watchdog with CONFIG_CPUMASK_OFFSTACK=y and flat APIC fcef8576d8a64fc603e719c97d423f9f6d4e0e8b converted backtrace_mask to a cpumask_var_t, and assumed check_nmi_watchdog was called before nmi_watchdog_tick was ever called. Steven's oops shows I was wrong. This is something of a bandaid: I'm not sure we *should* be calling nmi_watchdog_tick before check_nmi_watchdog. Note that gcc eliminates this test for the CONFIG_CPUMASK_OFFSTACK=n case. [ Impact: fix boot crash in rare configs ] Reported-by: Steven Rostedt Signed-off-by: Rusty Russell LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic/nmi.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel/apic/nmi.c') diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c index d6bd6240715..2ba52f35a88 100644 --- a/arch/x86/kernel/apic/nmi.c +++ b/arch/x86/kernel/apic/nmi.c @@ -414,7 +414,8 @@ nmi_watchdog_tick(struct pt_regs *regs, unsigned reason) touched = 1; } - if (cpumask_test_cpu(cpu, backtrace_mask)) { + /* We can be called before check_nmi_watchdog, hence NULL check. */ + if (backtrace_mask != NULL && cpumask_test_cpu(cpu, backtrace_mask)) { static DEFINE_SPINLOCK(lock); /* Serialise the printks */ spin_lock(&lock); -- cgit v1.2.3-70-g09d2 From fcc5c4a2feea3886dc058498b28508b2731720d5 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Tue, 21 Apr 2009 16:03:41 +0930 Subject: 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 Cc: Steven Rostedt LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/kernel/apic/nmi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/x86/kernel/apic/nmi.c') diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c index 2ba52f35a88..ce4fbfa315a 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 -- cgit v1.2.3-70-g09d2