From: Wanpeng Li <[email protected]> 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. Reported-by: Xiaolong Ye <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Luiz Capitulino <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Ingo Molnar <[email protected]> Signed-off-by: Wanpeng Li <[email protected]> --- 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
