On 2017-10-02 23:57:19 [-0400], Paul Gortmaker wrote: > On an older machine with a Pentium(R) Dual-Core E5300 I see the > the following early (see time stamps) boot splat on clock transition > due to TSC unstable (indicated in the last line): Would that work for you? >From 45aea321678856687927c53972321ebfab77759a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Date: Wed, 24 May 2017 08:52:02 +0200 Subject: [PATCH] sched/clock: Fix early boot preempt assumption in __set_sched_clock_stable() The more strict early boot preemption warnings found that __set_sched_clock_stable() was incorrectly assuming we'd still be running on a single CPU: BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 caller is debug_smp_processor_id+0x1c/0x1e CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.12.0-rc2-00108-g1c3c5ea #1 Call Trace: dump_stack+0x110/0x192 check_preemption_disabled+0x10c/0x128 ? set_debug_rodata+0x25/0x25 debug_smp_processor_id+0x1c/0x1e sched_clock_init_late+0x27/0x87 [...] Fix it by disabling IRQs. Reported-by: kernel test robot <xiaolong.ye@xxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: lkp@xxxxxx Cc: tipbuild@xxxxxxxxx Link: http://lkml.kernel.org/r/20170524065202.v25vyu7pvba5mhpd@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/clock.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 1a0d389d2f2b..ca0f8fc945c6 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -133,12 +133,19 @@ static void __scd_stamp(struct sched_clock_data *scd) static void __set_sched_clock_stable(void) { - struct sched_clock_data *scd = this_scd(); + struct sched_clock_data *scd; + /* + * Since we're still unstable and the tick is already running, we have + * to disable IRQs in order to get a consistent scd->tick* reading. + */ + local_irq_disable(); + scd = this_scd(); /* * Attempt to make the (initial) unstable->stable transition continuous. */ __sched_clock_offset = (scd->tick_gtod + __gtod_offset) - (scd->tick_raw); + local_irq_enable(); printk(KERN_INFO "sched_clock: Marking stable (%lld, %lld)->(%lld, %lld)\n", scd->tick_gtod, __gtod_offset, -- 2.14.2 -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
