Commit 2f537a9f authored Apr 21, 2009 by Rusty Russell Committed by Ingo Molnar Apr 21, 2009

x86: fix boot crash in NMI watchdog with CONFIG_CPUMASK_OFFSTACK=y and flat APIC



fcef8576 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 <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <alpine.DEB.2.00.0904202113520.10097@gandalf.stny.rr.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 06c38d5e

arch/x86/kernel/apic/nmi.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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);