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powerpc/xmon: Avoid tripping SMP hardlockup watchdog 

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>
This commit is contained in:
Nicholas Piggin 2017-09-29 13:29:40 +10:00 committed by Michael Ellerman
parent 80e4d70b06
commit 064996d62a
1 changed files with 13 additions and 4 deletions
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17
arch/powerpc/xmon/xmon.c
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@ -530,14 +530,19 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
waiting: waiting:
secondary = 1; secondary = 1;
spin_begin();
while (secondary && !xmon_gate) { while (secondary && !xmon_gate) {
if (in_xmon == 0) { if (in_xmon == 0) {
if (fromipi) if (fromipi) {
spin_end();
goto leave; goto leave;
}
secondary = test_and_set_bit(0, &in_xmon); secondary = test_and_set_bit(0, &in_xmon);
} }
barrier(); spin_cpu_relax();
touch_nmi_watchdog();
} }
spin_end();
if (!secondary && !xmon_gate) { if (!secondary && !xmon_gate) {
/* we are the first cpu to come in */ /* we are the first cpu to come in */
@ -568,21 +573,25 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
mb(); mb();
xmon_gate = 1; xmon_gate = 1;
barrier(); barrier();
touch_nmi_watchdog();
} }
cmdloop: cmdloop:
while (in_xmon) { while (in_xmon) {
if (secondary) { if (secondary) {
spin_begin();
if (cpu == xmon_owner) { if (cpu == xmon_owner) {
if (!test_and_set_bit(0, &xmon_taken)) { if (!test_and_set_bit(0, &xmon_taken)) {
secondary = 0; secondary = 0;
spin_end();
continue; continue;
} }
/* missed it */ /* missed it */
while (cpu == xmon_owner) while (cpu == xmon_owner)
barrier(); spin_cpu_relax();
} }
barrier(); spin_cpu_relax();
touch_nmi_watchdog();
} else { } else {
cmd = cmds(regs); cmd = cmds(regs);
if (cmd != 0) { if (cmd != 0) {