2017-07-07 20:01 GMT+08:00 Frederic Weisbecker <[email protected]>: > On Fri, Jul 07, 2017 at 02:08:25AM -0700, Wanpeng Li wrote: >> 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 >> >> This patch fixes it by replacing sched_clock_cpu() in vtime_delta() by >> local_clock() for effectively raw_smp_processor_id(). > > That's also broken because task_cputime() can be called from a different CPU > than > where the target task is running on, even though there shouldn't be practical > effect
Agreed. > as the clock must be stable but still the code would be confusing. > > No I think you can still use sched_clock(), just make sure you also use it on > arch_vtime_task_switch() and vtime_init_idle(). Is it acceptable to you, Peterz? :) Regards, Wanpeng Li
