From: Helge Deller <deller@xxxxxx>
commit 9dc4241bb14afecd16518a0760bceb3d7359b12a upstream.
This reverts commit afdb4a5b1d340e4afffc65daa21cc71890d7d589.
It triggers RCU stalls at boot with a 32-bit kernel.
Signed-off-by: Helge Deller <deller@xxxxxx>
Noticed-by: John David Anglin <dave.anglin@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.16+
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/parisc/kernel/time.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -249,16 +249,30 @@ void __init time_init(void)
static int __init init_cr16_clocksource(void)
{
/*
- * The cr16 interval timers are not syncronized across CPUs, even if
- * they share the same socket.
+ * The cr16 interval timers are not syncronized across CPUs on
+ * different sockets, so mark them unstable and lower rating on
+ * multi-socket SMP systems.
*/
if (num_online_cpus() > 1 && !running_on_qemu) {
- /* mark sched_clock unstable */
- clear_sched_clock_stable();
+ int cpu;
+ unsigned long cpu0_loc;
+ cpu0_loc = per_cpu(cpu_data, 0).cpu_loc;
- clocksource_cr16.name = "cr16_unstable";
- clocksource_cr16.flags = CLOCK_SOURCE_UNSTABLE;
- clocksource_cr16.rating = 0;
+ for_each_online_cpu(cpu) {
+ if (cpu == 0)
+ continue;
+ if ((cpu0_loc != 0) &&
+ (cpu0_loc == per_cpu(cpu_data, cpu).cpu_loc))
+ continue;
+
+ /* mark sched_clock unstable */
+ clear_sched_clock_stable();
+
+ clocksource_cr16.name = "cr16_unstable";
+ clocksource_cr16.flags = CLOCK_SOURCE_UNSTABLE;
+ clocksource_cr16.rating = 0;
+ break;
+ }
}
/* register at clocksource framework */
