libusb阻塞
转自：http://leave001.blog.163.com/blog/static/162691293201252111745737/
usb指纹头出现了一点状况，若libusb以同步方式发送bulk transfer出现阻塞。经过测试发现跟timeout有些关系：若timeout为0（无timeout），不会阻塞；若timeout为1000或者2000，则会。另外，若采用异步方式传送bulk transfer，则不会阻塞。
static int do_sync_bulk_transfer ( struct libusb_device_handle * dev_handle ,unsigned char endpoint , unsigned char * buffer , int length ,int * transferred , unsigned int timeout , unsigned char type ){libusb_fill_bulk_transfer ( transfer , dev_handle , endpoint , buffer , length ,bulk_transfer_cb , & completed , timeout );transfer -> type = type ;r = libusb_submit_transfer ( transfer );if ( r < 0 ) {libusb_free_transfer ( transfer );return r ;}while (! completed ) {r = libusb_handle_events ( HANDLE_CTX ( dev_handle ));}}
found usbfs at /dev/bus/usb found usb devices in sysfs add fd 9 events 1 created default context scan usb1 sysfs descriptors available bus=1 dev=1 busnum 1 devaddr 1 session_id 257 allocating new device for 1/1 (session 257) scan 1-1 bus=1 dev=2 busnum 1 devaddr 2 session_id 258 allocating new device for 1/2 (session 258) scan 1-1.1 bus=1 dev=3 busnum 1 devaddr 3 session_id 259 allocating new device for 1/3 (session 259) open 1.3 add fd 11 events 4 destroy device 1.1 destroy device 1.2 configuration 1 interface 0 next timeout in 2.499878s poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=2 status=0 transferred=0 handling completion status 0 actual_length=0 （control transfer的回调） next timeout in 2.499909s poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=2 status=0 transferred=0 handling completion status 0 actual_length=0（另一个control transfer的回调） need 10 urbs for new transfer with length 153600 next timeout in 0.997836s （从这里开始查询bulk） poll() 2 fds with timeout in 998ms poll() returned 1 urb type=3 status=0 transferred=16384 handling completion status 0 of bulk urb 1/10 next timeout in 0.379086s poll() 2 fds with timeout in 380ms poll() returned 1 urb type=3 status=0 transferred=16384 handling completion status 0 of bulk urb 2/10 next timeout in 0.253080s poll() 2 fds with timeout in 254ms poll() returned 0 all URBs have already been processed for timeouts （超时） poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=9728 handling completion status -2 of bulk urb 3/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=0 handling completion status -2 of bulk urb 4/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=0 handling completion status -2 of bulk urb 5/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=0 handling completion status -2 of bulk urb 6/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=0 handling completion status -2 of bulk urb 7/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=0 handling completion status -2 of bulk urb 8/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=0 handling completion status -2 of bulk urb 9/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 1 urb type=3 status=-2 transferred=0 handling completion status -2 of bulk urb 10/10 CANCEL: detected a cancelled URB all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 0 all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 0 all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 0 all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 0 all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 0 all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 0 all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms poll() returned 0 all URBs have already been processed for timeouts poll() 2 fds with timeout in 2000ms ^C
e8c3a240 1032172219 S Co:1:003:0 s 00 09 0001 0000 0000 0 e8c3a240 1032173347 C Co:1:003:0 0 0 e8c3a240 1032174262 S Co:1:003:0 s 40 e0 0000 0000 0000 0 e8c3a240 1032174597 C Co:1:003:0 0 0 e8c3a240 1032175054 S Co:1:003:0 s 02 01 0000 0081 0000 0 e8c3a240 1032249749 C Co:1:003:0 0 0 e8c3a240 1032250298 S Co:1:003:0 s 40 e5 0000 0000 0000 0 e8c3a240 1032250634 C Co:1:003:0 0 0 e8c3a240 1032251121 S Bi:1:003:1 -115 16384 < e8c3a440 1032251365 S Bi:1:003:1 -115 16384 < e8c3a1c0 1032252890 S Bi:1:003:1 -115 16384 < e8c3a2c0 1032254018 S Bi:1:003:1 -115 16384 < e8c3a740 1032254475 S Bi:1:003:1 -115 16384 < e8c3a7c0 1032254871 S Bi:1:003:1 -115 16384 < e8c3a5c0 1032255268 S Bi:1:003:1 -115 16384 < e8c3a0c0 1032255695 S Bi:1:003:1 -115 16384 < e8c3a640 1032256091 S Bi:1:003:1 -115 16384 < e849ce20 1032256518 S Bi:1:003:1 -115 6144 < e8c3a240 1032561640 C Bi:1:003:1 0 16384 = 40e50000 00000000 a59fa89e b3a3a09c a899989b 8b8a9ba0 9f9392a0 929f8498 e8c3a440 1033162310 C Bi:1:003:1 0 16384 = 909e8a92 8d99898d 908f9490 9ba197a1 8ba5a69d 9396959d 948d9e9e 968c9584 e8c3a1c0 1033653347 C Bi:1:003:1 0 16384 = d1d9d0d8 d3cdd2d7 d1d8c5d6 c5cfd1d3 d0ccd0d4 d0cbd1d1 bed2d2d0 d9dad4d9 e8c3a2c0 1034152250 C Bi:1:003:1 0 16384 = a79fa0aa ada2bab2 b6b3a5ad aeae9bb0 b2aa9eaa 9396a8a6 afa5af95 9daaa5ba e8c3a740 1034753624 C Bi:1:003:1 -2 16320 = d6d0d5d2 ccd4c7cc cdd6cfc9 d3d2d2ce cfcfd5c8 d0c4cdc7 cdc9c6ca d4d0cec2 e8c3a2c0 1034753776 S Co:1:002:0 s 23 08 9031 0001 0000 0 e8c3a2c0 1034754111 C Co:1:002:0 0 0 e8c3a7c0 1034755026 C Bi:1:003:1 -2 64 = a3a9bda3 a5a4a9a5 93a69e98 949d9294 aa9d8d9d 9b91a6a4 a793a097 9b8f8f96 e8c3a2c0 1034755117 S Co:1:002:0 s 23 08 9031 0001 0000 0 e8c3a2c0 1034755483 C Co:1:002:0 0 0 e8c3a5c0 1034756215 C Bi:1:003:1 -2 64 = d1c7d2d5 dad6d6db ded1d0da d8d2d4da d3d8d8d6 dbd4dedd d2d5ded5 dbd6d7d8 e8c3a2c0 1034756459 S Co:1:002:0 s 23 08 9031 0001 0000 0 e8c3a2c0 1034756855 C Co:1:002:0 0 0 e8c3a0c0 1034757587 C Bi:1:003:1 -2 64 = b04a5e59 637c8270 7f848378 7f7e7881 838f8497 988a8389 938c8f92 8b8ca28c e8c3a2c0 1034757648 S Co:1:002:0 s 23 08 9031 0001 0000 0 e8c3a2c0 1034757983 C Co:1:002:0 0 0 e8c3a640 1034758715 C Bi:1:003:1 -2 0 e8c3a2c0 1034758776 S Co:1:002:0 s 23 08 9031 0001 0000 0 e8c3a2c0 1034759111 C Co:1:002:0 0 0 e849ce20 1034759569 C Bi:1:003:1 -2 0 e8c3a2c0 1034759630 S Co:1:002:0 s 23 08 9031 0001 0000 0 e8c3a2c0 1034759995 C Co:1:002:0 0 0