• Wanpeng Li's avatar
    sched/cputime: Don't use smp_processor_id() in preemptible context · 0e4097c3
    Wanpeng Li authored
    Recent kernels trigger this warning:
    
     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-g2a42eb95 #1
     Call Trace:
      dump_stack+0x82/0xb8
      check_preemption_disabled()
      debug_smp_processor_id()
      vtime_delta()
      task_cputime()
      thread_group_cputime()
      thread_group_cputime_adjusted()
      wait_consider_task()
      do_wait()
      SYSC_wait4()
      do_syscall_64()
      entry_SYSCALL64_slow_path()
    
    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() with sched_clock() to
    avoid calling smp_processor_id() in a preemptible context.
    Reported-by: default avatarXiaolong Ye <xiaolong.ye@intel.com>
    Signed-off-by: default avatarWanpeng Li <wanpeng.li@hotmail.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Luiz Capitulino <lcapitulino@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/1499586028-7402-1-git-send-email-wanpeng.li@hotmail.com
    [ Prettified the changelog. ]
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    0e4097c3