Peter,
The problem is in this stack
start_kernel
local_irq_enable
late_time_init
sched_clock_init
generic_sched_clock_init
sched_clock_register
WARN_ON(!irqs_disabled());
Before this work, sched_clock_init() was called prior to enabling
interrupts, but now after. So, we hit this WARN_ON() in
sched_clock_register().
The question is why do we need this warning in sched_clock_register? I
guess because we want to make this section of the code atomic:
195 new_epoch = read(); <- from here
196 cyc = cd.actual_read_sched_clock();
197 ns = rd.epoch_ns + cyc_to_ns((cyc - rd.epoch_cyc) &
rd.sched_clock_mask, rd.mult, rd.shift);
198 cd.actual_read_sched_clock = read;
199
200 rd.read_sched_clock = read;
201 rd.sched_clock_mask = new_mask;
202 rd.mult = new_mult;
203 rd.shift = new_shift;
204 rd.epoch_cyc = new_epoch;
205 rd.epoch_ns = ns;
206
207 update_clock_read_data(&rd); <- to here
If we need it, we can surround the sched_clock_register() with
local_irq_disable/local_irq_enable:
diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index cbc72c2c1fca..5015b165b55b 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -243,8 +243,11 @@ void __init generic_sched_clock_init(void)
* If no sched_clock() function has been provided at that point,
* make it the final one one.
*/
- if (cd.actual_read_sched_clock == jiffy_sched_clock_read)
+ if (cd.actual_read_sched_clock == jiffy_sched_clock_read) {
+ local_irq_disable();
sched_clock_register(jiffy_sched_clock_read, BITS_PER_LONG, HZ);
+ local_irq_enable();
+ }
update_sched_clock();
Thank you,
Pavel
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