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') diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c index d6bd624..2ba52f3 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 v1.1