alexander.levin@xxxxxxxxxxx writes:
> From: Nicholas Piggin <npiggin@xxxxxxxxx>
>
> [ Upstream commit 064996d62a33ffe10264b5af5dca92d54f60f806 ]
>
> The SMP hardlockup watchdog cross-checks other CPUs for lockups, which
> causes xmon headaches because it's assuming interrupts hard disabled
> means no watchdog troubles. Try to improve that by calling
> touch_nmi_watchdog() in obvious places where secondaries are spinning.
>
> Also annotate these spin loops with spin_begin/end calls.
These macros didn't exist until 4.13, and haven't been backported AFAIK.
cheers
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index e23f559faa47..6cec1081cb67 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -436,14 +436,19 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
>
> waiting:
> secondary = 1;
> + spin_begin();
> while (secondary && !xmon_gate) {
> if (in_xmon == 0) {
> - if (fromipi)
> + if (fromipi) {
> + spin_end();
> goto leave;
> + }
> secondary = test_and_set_bit(0, &in_xmon);
> }
> - barrier();
> + spin_cpu_relax();
> + touch_nmi_watchdog();
> }
> + spin_end();
>
> if (!secondary && !xmon_gate) {
> /* we are the first cpu to come in */
> @@ -470,21 +475,25 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
> mb();
> xmon_gate = 1;
> barrier();
> + touch_nmi_watchdog();
> }
>
> cmdloop:
> while (in_xmon) {
> if (secondary) {
> + spin_begin();
> if (cpu == xmon_owner) {
> if (!test_and_set_bit(0, &xmon_taken)) {
> secondary = 0;
> + spin_end();
> continue;
> }
> /* missed it */
> while (cpu == xmon_owner)
> - barrier();
> + spin_cpu_relax();
> }
> - barrier();
> + spin_cpu_relax();
> + touch_nmi_watchdog();
> } else {
> cmd = cmds(regs);
> if (cmd != 0) {
> --
> 2.11.0