Busy loop calling futex, 100% CPU usage

[markferry]

Intermittent but seen on two occasions recently.

futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                    [55/432]
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0xc000100848, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=2446, si_uid=128} ---                                                                                                                                                                  
rt_sigreturn({mask=[]})                 = 6                                                                                                                                                                                                  
futex(0xc000100148, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0xc000100848, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=2446, si_uid=128} ---                                                                                                                                                                  
rt_sigreturn({mask=[]})                 = 6                                                                                                                                                                                                  
futex(0xc000100148, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0xc000100848, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=2446, si_uid=128} ---                                                                                                                                                                  
rt_sigreturn({mask=[]})                 = 824637841104                                                                                                                                                                                       
futex(0xc000100148, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0xc000100848, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=2446, si_uid=128} ---                                                                                                                                                                  
rt_sigreturn({mask=[]})                 = 824637841104                                                                                                                                                                                       
futex(0xc000100148, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0xc000100848, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=2446, si_uid=128} ---                                                                                                                                                                  
rt_sigreturn({mask=[]})                 = 6                                                                                                                                                                                                  
futex(0xc000100148, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0xc000100848, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=2446, si_uid=128} ---                                                                                                                                                                  
rt_sigreturn({mask=[]})                 = 824637841104                                                                                                                                                                                       
futex(0xc000100148, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0xc000100848, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
--- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=2446, si_uid=128} ---                                                                                                                                                                  
rt_sigreturn({mask=[]})                 = 824637841104                                                                                                                                                                                       
futex(0xc000100148, FUTEX_WAKE_PRIVATE, 1) = 1                                                                                                                                                                                               
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                                                                                                                                                            
futex(0x1255a00, FUTEX_WAIT_PRIVATE, 0, NULL) = 0                                                         

[markferry]

busy-lsof.txt

busy-objdump.txt.gz

busy-pmap.txt

[markferry]

$ sudo netstat -pnt  | grep 2446
tcp        0      0 192.168.7.5:34330       34.158.255.62:443       ESTABLISHED 2446/go-librespot   
tcp6       0      0 127.0.0.1:24807         127.0.0.1:34484         ESTABLISHED 2446/go-librespot   

$ host 34.158.255.62
62.255.158.34.in-addr.arpa domain name pointer 62.255.158.34.bc.googleusercontent.com.

[devgianlu]

I'd say the most useful thing here would be a goroutine dump. You can trigger it by sending SIGABRT to the process.

[markferry]

Had to kill the process. I'll catch it next time.