Messages in this thread Patch in this message | | | Date | Wed, 24 May 2017 03:18:56 -0700 | From | tip-bot for Peter Zijlstra <> | Subject | [tip:sched/core] sched/clock: Fix early boot preempt assumption in __set_sched_clock_stable() |
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Commit-ID: 45aea321678856687927c53972321ebfab77759a Gitweb: http://git.kernel.org/tip/45aea321678856687927c53972321ebfab77759a Author: Peter Zijlstra <peterz@infradead.org> AuthorDate: Wed, 24 May 2017 08:52:02 +0200 Committer: Ingo Molnar <mingo@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.ye@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: lkp@01.org Cc: tipbuild@zytor.com Link: http://lkml.kernel.org/r/20170524065202.v25vyu7pvba5mhpd@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@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,
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