From 97f41b41c432e5a80c91445d92c2f4b729984d36 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Fri, 29 Sep 2017 13:29:40 +1000 Subject: [PATCH] powerpc/xmon: Avoid tripping SMP hardlockup watchdog [ 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. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/xmon/xmon.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index c008083fbc4f..2c8b325591cc 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -530,14 +530,19 @@ 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 */ @@ -568,21 +573,25 @@ 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