On Wed, Jul 19, 2017 at 4:38 PM, Paul McKenney <paulmck...@gmail.com> wrote:
> On Thu, Jul 13, 2017 at 11:49 PM, Wanpeng Li <kernel...@gmail.com> wrote:
>>
>> Ping for the merge window. :)
>> 2017-07-09 15:40 GMT+08:00 Wanpeng Li <kernel...@gmail.com>:
>> > From: Wanpeng Li <wanpeng...@hotmail.com>
>> >
>> > BUG: using smp_processor_id() in preemptible [00000000] code:
>> > 99-trinity/181
>> > caller is debug_smp_processor_id+0x17/0x19
>> > CPU: 0 PID: 181 Comm: 99-trinity Not tainted 4.12.0-01059-g2a42eb9 #1
>> > Call Trace:
>> > dump_stack+0x82/0xb8
>> > check_preemption_disabled+0xd1/0xe3
>> > debug_smp_processor_id+0x17/0x19
>> > vtime_delta+0xd/0x2c
>> > task_cputime+0x89/0xdb
>> > thread_group_cputime+0x11b/0x1ed
>> > thread_group_cputime_adjusted+0x1f/0x47
>> > wait_consider_task+0x2a9/0xaf9
>> > ? lock_acquire+0x97/0xa4
>> > do_wait+0xdf/0x1f4
>> > SYSC_wait4+0x8e/0xb5
>> > ? list_add+0x34/0x34
>> > SyS_wait4+0x9/0xb
>> > do_syscall_64+0x70/0x82
>> > entry_SYSCALL64_slow_path+0x25/0x25
>> >
>> > As Frederic pointed out:
>> >
>> > | Although those sched_clock_cpu() things seem to only matter when the
>> > | sched_clock() is unstable. And that stability is a condition for
>> > nohz_full
>> > | to work anyway. So probably sched_clock() alone would be enough.
>> >
>> > This patch fixes it by replacing sched_clock_cpu() by sched_clock() to
>> > avoid to call smp_processor_id() in preemptible context.
>
>
> I am hitting this with rcutorture, so have kicked off an overnight
> run with this patch.
Which passed, so:
Tested-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Thanx, Paul
>> > Reported-by: Xiaolong Ye <xiaolong...@intel.com>
>> > Cc: Thomas Gleixner <t...@linutronix.de>
>> > Cc: Luiz Capitulino <lcapitul...@redhat.com>
>> > Cc: Frederic Weisbecker <fweis...@gmail.com>
>> > Cc: Rik van Riel <r...@redhat.com>
>> > Cc: Peter Zijlstra <pet...@infradead.org>
>> > Cc: Ingo Molnar <mi...@kernel.org>
>> > Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com>
>> > ---
>> > kernel/sched/cputime.c | 6 +++---
>> > 1 file changed, 3 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
>> > index 6e3ea4a..14d2dbf 100644
>> > --- a/kernel/sched/cputime.c
>> > +++ b/kernel/sched/cputime.c
>> > @@ -683,7 +683,7 @@ static u64 vtime_delta(struct vtime *vtime)
>> > {
>> > unsigned long long clock;
>> >
>> > - clock = sched_clock_cpu(smp_processor_id());
>> > + clock = sched_clock();
>> > if (clock < vtime->starttime)
>> > return 0;
>> >
>> > @@ -814,7 +814,7 @@ void arch_vtime_task_switch(struct task_struct
>> > *prev)
>> >
>> > write_seqcount_begin(&vtime->seqcount);
>> > vtime->state = VTIME_SYS;
>> > - vtime->starttime = sched_clock_cpu(smp_processor_id());
>> > + vtime->starttime = sched_clock();
>> > write_seqcount_end(&vtime->seqcount);
>> > }
>> >
>> > @@ -826,7 +826,7 @@ void vtime_init_idle(struct task_struct *t, int cpu)
>> > local_irq_save(flags);
>> > write_seqcount_begin(&vtime->seqcount);
>> > vtime->state = VTIME_SYS;
>> > - vtime->starttime = sched_clock_cpu(cpu);
>> > + vtime->starttime = sched_clock();
>> > write_seqcount_end(&vtime->seqcount);
>> > local_irq_restore(flags);
>> > }
>> > --
>> > 2.7.4
>> >
>
>
