Commit-ID: 45aea321678856687927c53972321ebfab77759a Gitweb: http://git.kernel.org/tip/45aea321678856687927c53972321ebfab77759a Author: Peter Zijlstra <pet...@infradead.org> AuthorDate: Wed, 24 May 2017 08:52:02 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 24 May 2017 09:10:00 +0200
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...@intel.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Acked-by: Thomas Gleixner <t...@linutronix.de> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mark Rutland <mark.rutl...@arm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Steven Rostedt <rost...@goodmis.org> Cc: l...@01.org Cc: tipbu...@zytor.com Link: http://lkml.kernel.org/r/20170524065202.v25vyu7pvba5m...@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mi...@kernel.org> --- 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 1a0d389..ca0f8fc 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,
