Here are some backtraces
Normal CPU usage:
Thread 5 (Thread 0x7f6365c82700 (LWP 30482)):
#0 0x00007f6366196b6d in poll () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f6365c92b3c in ?? () from /lib/x86_64-linux-gnu/libusb-1.0.so.0
#2 0x00007f6366462284 in start_thread (arg=0x7f6365c82700) at
pthread_create.c:333
#3 0x00007f636619fa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 4 (Thread 0x7f6365481700 (LWP 30483)):
#0 0x00007f6366196b6d in poll () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f6365c92b3c in ?? () from /lib/x86_64-linux-gnu/libusb-1.0.so.0
#2 0x00007f6366462284 in start_thread (arg=0x7f6365481700) at
pthread_create.c:333
#3 0x00007f636619fa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 3 (Thread 0x7f6364c80700 (LWP 30484)):
#0 0x00007f6366196b6d in poll () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f6365c8c0b5 in ?? () from /lib/x86_64-linux-gnu/libusb-1.0.so.0
#2 0x00007f6365c8d043 in libusb_handle_events_timeout_completed () from
/lib/x86_64-linux-gnu/libusb-1.0.so.0
#3 0x00007f6365c8d12f in libusb_handle_events () from
/lib/x86_64-linux-gnu/libusb-1.0.so.0
#4 0x00007f6365ea9004 in ?? () from
/usr/lib/pcsc/drivers/ifd-ccid.bundle/Contents/Linux/libccid.so
#5 0x00007f6365ea3853 in ?? () from
/usr/lib/pcsc/drivers/ifd-ccid.bundle/Contents/Linux/libccid.so
#6 0x00000000004061a3 in EHStatusHandlerThread (rContext=0x177a010) at
eventhandler.c:464
#7 0x00007f6366462284 in start_thread (arg=0x7f6364c80700) at
pthread_create.c:333
#8 0x00007f636619fa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 2 (Thread 0x7f635ffff700 (LWP 30485)):
#0 0x00007f6366196b6d in poll () at ../sysdeps/unix/syscall-template.S:81
#1 0x000000000040e61a in HPEstablishUSBNotifications (arg=0x17a4a30) at
hotplug_libudev.c:624
#2 0x00007f6366462284 in start_thread (arg=0x7f635ffff700) at
pthread_create.c:333
#3 0x00007f636619fa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 1 (Thread 0x7f6366c51740 (LWP 30481)):
#0 0x00007f6366198963 in select () at ../sysdeps/unix/syscall-template.S:81
#1 0x0000000000411179 in ProcessEventsServer
(pdwClientID=pdwClientID@entry=0x7ffea88638a0)
at winscard_msg_srv.c:223
#2 0x00000000004035c1 in SVCServiceRunLoop () at pcscdaemon.c:128
#3 main (argc=<optimized out>, argv=<optimized out>) at pcscdaemon.c:685
100% CPU:
Thread 5 (Thread 0x7f1969ee2700 (LWP 30237)):
#0 0x00007f196a6cabdd in recvmsg () at
../sysdeps/unix/syscall-template.S:81
#1 0x00007f196aebe6ec in udev_monitor_receive_device () from
/lib/x86_64-linux-gnu/libudev.so.1
#2 0x00007f1969ef2bcb in ?? () from /lib/x86_64-linux-gnu/libusb-1.0.so.0
#3 0x00007f196a6c2284 in start_thread (arg=0x7f1969ee2700) at
pthread_create.c:333
#4 0x00007f196a3ffa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 4 (Thread 0x7f19696e1700 (LWP 30238)):
#0 0x00007f196a3f6b6d in poll () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f1969ef2b3c in ?? () from /lib/x86_64-linux-gnu/libusb-1.0.so.0
#2 0x00007f196a6c2284 in start_thread (arg=0x7f19696e1700) at
pthread_create.c:333
#3 0x00007f196a3ffa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 3 (Thread 0x7f1968ee0700 (LWP 30239)):
#0 0x00007f196a3f6b6d in poll () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f1969eec0b5 in ?? () from /lib/x86_64-linux-gnu/libusb-1.0.so.0
#2 0x00007f1969eed043 in libusb_handle_events_timeout_completed () from
/lib/x86_64-linux-gnu/libusb-1.0.so.0
#3 0x00007f1969eed12f in libusb_handle_events () from
/lib/x86_64-linux-gnu/libusb-1.0.so.0
#4 0x00007f196a109004 in ?? () from
/usr/lib/pcsc/drivers/ifd-ccid.bundle/Contents/Linux/libccid.so
#5 0x00007f196a103853 in ?? () from
/usr/lib/pcsc/drivers/ifd-ccid.bundle/Contents/Linux/libccid.so
#6 0x00000000004061a3 in EHStatusHandlerThread (rContext=0xd49010) at
eventhandler.c:464
#7 0x00007f196a6c2284 in start_thread (arg=0x7f1968ee0700) at
pthread_create.c:333
#8 0x00007f196a3ffa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 2 (Thread 0x7f1963fff700 (LWP 30240)):
#0 0x00007f196a3f6b6d in poll () at ../sysdeps/unix/syscall-template.S:81
#1 0x000000000040e61a in HPEstablishUSBNotifications (arg=0xd73a30) at
hotplug_libudev.c:624
#2 0x00007f196a6c2284 in start_thread (arg=0x7f1963fff700) at
pthread_create.c:333
#3 0x00007f196a3ffa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 1 (Thread 0x7f196aeb1740 (LWP 30236)):
#0 0x00007f196a3f8963 in select () at ../sysdeps/unix/syscall-template.S:81
#1 0x0000000000411179 in ProcessEventsServer
(pdwClientID=pdwClientID@entry=0x7ffc0e4e4240) at winscard_msg_srv.c:223
#2 0x00000000004035c1 in SVCServiceRunLoop () at pcscdaemon.c:128
#3 main (argc=<optimized out>, argv=<optimized out>) at pcscdaemon.c:685
So the difference is in this thread and udev indeed:
#0 0x00007f196a6cabdd in recvmsg () at ../sysdeps/unix/syscall-template.S:81
#1 0x00007f196aebe6ec in udev_monitor_receive_device () from
/lib/x86_64-linux-gnu/libudev.so.1
#2 0x00007f1969ef2bcb in ?? () from /lib/x86_64-linux-gnu/libusb-1.0.so.0
#3 0x00007f196a6c2284 in start_thread (arg=0x7f1969ee2700) at
pthread_create.c:333
#4 0x00007f196a3ffa4d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:109
