This is a note to let you know that I've just added the patch titled
powerpc/xmon: Avoid tripping SMP hardlockup watchdog
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-xmon-avoid-tripping-smp-hardlockup-watchdog.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Wed Dec 20 18:17:52 CET 2017
From: Nicholas Piggin <npiggin@xxxxxxxxx>
Date: Fri, 29 Sep 2017 13:29:40 +1000
Subject: powerpc/xmon: Avoid tripping SMP hardlockup watchdog
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.
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/xmon/xmon.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -530,14 +530,19 @@ static int xmon_core(struct pt_regs *reg
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 *reg
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) {
Patches currently in stable-queue which might be from npiggin@xxxxxxxxx are
queue-4.14/cpuidle-fix-broadcast-control-when-broadcast-can-not-be-entered.patch
queue-4.14/powerpc-xmon-avoid-tripping-smp-hardlockup-watchdog.patch
queue-4.14/powerpc-watchdog-do-not-trigger-smp-crash-from-touch_nmi_watchdog.patch