From: Nicholas Piggin npiggin@gmail.com
[ 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 npiggin@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin alexander.levin@verizon.com --- 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 760545519a0b..05751c9e7f53 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -496,14 +496,19 @@ 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 */ @@ -530,21 +535,25 @@ 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) {