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authorPaul E. McKenney <paulmck@kernel.org>2020-07-08 16:25:43 -0700
committerPaul E. McKenney <paulmck@kernel.org>2020-08-24 14:24:25 -0700
commit160c7ba34605d9b59ee406a1b4a61b0f942b1ae9 (patch)
tree6bb20cf2018927bc9fd28b8357a3e7d0410e06fc /lib/nmi_backtrace.c
parent9123e3a74ec7b934a4a099e98af6a61c2f80bbf5 (diff)
lib: Add backtrace_idle parameter to force backtrace of idle CPUs
Currently, the nmi_cpu_backtrace() declines to produce backtraces for idle CPUs. This is a good choice in the common case in which problems are caused only by non-idle CPUs. However, there are occasionally situations in which idle CPUs are helping to cause problems. This commit therefore adds an nmi_backtrace.backtrace_idle kernel boot parameter that causes nmi_cpu_backtrace() to dump stacks even of idle CPUs. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <linux-doc@vger.kernel.org>
Diffstat (limited to 'lib/nmi_backtrace.c')
-rw-r--r--lib/nmi_backtrace.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
index 15ca78e1c7d4..8abe1870dba4 100644
--- a/lib/nmi_backtrace.c
+++ b/lib/nmi_backtrace.c
@@ -85,12 +85,16 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
put_cpu();
}
+// Dump stacks even for idle CPUs.
+static bool backtrace_idle;
+module_param(backtrace_idle, bool, 0644);
+
bool nmi_cpu_backtrace(struct pt_regs *regs)
{
int cpu = smp_processor_id();
if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
- if (regs && cpu_in_idle(instruction_pointer(regs))) {
+ if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
cpu, (void *)instruction_pointer(regs));
} else {