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):
[ 2.487904] BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1
[ 2.487909] caller is debug_smp_processor_id+0x17/0x20
[ 2.487911] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.11.12-rt14-00451
[ 2.487911] Hardware name: Dell Inc. OptiPlex 760 /0M858N, BIOS A16 08/06/2013
[ 2.487912] Call Trace:
[ 2.487918] dump_stack+0x4f/0x6a
[ 2.487919] check_preemption_disabled+0xda/0xe0
[ 2.487921] debug_smp_processor_id+0x17/0x20
[ 2.487924] clear_sched_clock_stable+0x28/0x80
[ 2.487927] mark_tsc_unstable+0x22/0x70
[ 2.487930] acpi_processor_get_power_info+0x3e3/0x6a0
[ 2.487932] acpi_processor_power_init+0x3a/0x1d0
[ 2.487933] __acpi_processor_start+0x162/0x1b0
....
[ 2.487950] acpi_processor_driver_init+0x20/0x96
[ 2.487951] do_one_initcall+0x3f/0x170
[ 2.487954] kernel_init_freeable+0x18e/0x216
[ 2.487955] ? rest_init+0xd0/0xd0
[ 2.487956] kernel_init+0x9/0x100
[ 2.487958] ret_from_fork+0x22/0x30
[ 2.487960] sched_clock: Marking unstable (2488005383, -223143)<-(2590866395, -103084155)
[ 2.488004] tsc: Marking TSC unstable due to TSC halts in idle
(gdb) list *clear_sched_clock_stable+0x28
0xffffffff8108bbb8 is in clear_sched_clock_stable (kernel/sched/clock.c:114).
[...]
112 static inline struct sched_clock_data *this_scd(void)
113 {
114 return this_cpu_ptr(&sched_clock_data);
115 }
We now get this_scd with preemption disabled. I also decided to pass
in the scd to __clear_sched_clock_stable in the hope it made it more
clear that the caller (currently only one) needs to get this_scd with
preemption disabled, even though that wasn't strictly required.
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
index 11ad4bd995e2..32dcda23c616 100644
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -155,9 +155,8 @@ static void __sched_clock_work(struct work_struct *work)
static DECLARE_WORK(sched_clock_work, __sched_clock_work);
-static void __clear_sched_clock_stable(void)
+static void __clear_sched_clock_stable(struct sched_clock_data *scd)
{
- struct sched_clock_data *scd = this_scd();
/*
* Attempt to make the stable->unstable transition continuous.
@@ -186,8 +185,14 @@ void clear_sched_clock_stable(void)
smp_mb(); /* matches sched_clock_init_late() */
- if (sched_clock_running == 2)
- __clear_sched_clock_stable();
+ if (sched_clock_running == 2) {
+ struct sched_clock_data *scd;
+
+ preempt_disable();
+ scd = this_scd();
+ preempt_enable();
+ __clear_sched_clock_stable(scd);
+ }
}
void sched_clock_init_late(void)
--
2.1.4
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