From: Rusty Russell Date: Tue, 21 Apr 2009 06:30:15 +0000 (+0930) Subject: x86: fix boot crash in NMI watchdog with CONFIG_CPUMASK_OFFSTACK=y and flat APIC X-Git-Tag: v2.6.30-rc4~29^2~7 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=2f537a9f8e82f55c241b002c8cfbf34303b45ada;p=karo-tx-linux.git 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 --- diff --git a/arch/x86/kernel/apic/nmi.c b/arch/x86/kernel/apic/nmi.c index d6bd62407152..2ba52f35a88c 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);