On 6/28/21 7:25 AM, lijinlin wrote: > From: lijinlin <lijinlin3@xxxxxxxxxx> > > We found blktrace got stuck when cgroup restricts blktrace to use cpu, > the messages and stack is: > [root@localhost ~]# blktrace -w 10 -o- /dev/sda > FAILED to start thread on CPU 1: 22/Invalid argument > FAILED to start thread on CPU 2: 22/Invalid argument > [root@localhost ~]# cat /proc/1385110/stack > [<0>] __switch_to+0xe8/0x150 > [<0>] futex_wait_queue_me+0xd4/0x158 > [<0>] futex_wait+0xf4/0x230 > [<0>] do_futex+0x470/0x900 > [<0>] __arm64_sys_futex+0x13c/0x188 > [<0>] el0_svc_common+0x80/0x200 > [<0>] el0_svc_handler+0x78/0xe0 > [<0>] el0_svc+0x10/0x260 > [<0>] 0xffffffffffffffff > > Blktrace failed to start thread is caused by thread can't lock on the > Restricted cpu. In this case, blktrace would't schedule an alarm after > defined time to set variable 'done' as 1. > We debug the code and found the call trace as bellow: > main() > ==>run_tracers() > ==>wait_tracers() > ==>process_trace_bufs() > ==>wait_empty_entries() > ==>t_pthread_cond_wait() > Blktrace was set to piped output, so the process is stuck in > wait_empty_entries() for wait variable 'done' have been set as 1. > > We set variable 'done' as 1 when 'nthreads_running' is not equal to > 'ncpus' in run_tracers() to fix the problem. Applied, thanks. -- Jens Axboe
