Hi, while playing with suspend to ram I found a strange behavior with usb persistence. This can be easily reproduce by doing : - plug a usb key - start to read the usb key : "cat /dev/sdx > /dev/null" - go to suspend : "echo mem > /sys/power/state" - while in suspend, unplug and replug the usb key (simulate usb power loss for computer that keep power) - exit suspend - there is read error on the usb key Because the power was cut during s2ram, the usb stack reset the device <1>. But when the user task restart, the usb storage device do not seem ready to accept data traffic <2>, and IO error are returned to user space application. It look like the device need some delay after the reset (800ms between reset and <3>). Shouldn't we wait that the device is ready before restart IO on the device ? Matthieu <1> [ 117.070255] usb 2-1.4: reset high-speed USB device number 3 using ehci-pci [...] [ 117.543922] Restarting tasks ... done. [ 117.548390] video LNXVIDEO:01: Restoring backlight state <2> [ 117.549179] sd 6:0:0:0: [sdb] Media Changed [ 117.549184] sd 6:0:0:0: [sdb] [ 117.549187] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 117.549189] sd 6:0:0:0: [sdb] [ 117.549191] Sense Key : Unit Attention [current] [ 117.549195] Info fld=0x0 [ 117.549197] sd 6:0:0:0: [sdb] [ 117.549201] Add. Sense: Not ready to ready change, medium may have changed [ 117.549203] sd 6:0:0:0: [sdb] CDB: [ 117.549205] Read(10): 28 00 00 02 c9 00 00 00 f0 00 [ 117.549212] end_request: I/O error, dev sdb, sector 182528 [ 117.549218] Buffer I/O error on device sdb1, logical block 22560 [ 117.549225] Buffer I/O error on device sdb1, logical block 22561 [ 117.549228] Buffer I/O error on device sdb1, logical block 22562 [ 117.549231] Buffer I/O error on device sdb1, logical block 22563 [ 117.549233] Buffer I/O error on device sdb1, logical block 22564 [ 117.549235] Buffer I/O error on device sdb1, logical block 22565 [ 117.549238] Buffer I/O error on device sdb1, logical block 22566 [ 117.549240] Buffer I/O error on device sdb1, logical block 22567 [ 117.549243] Buffer I/O error on device sdb1, logical block 22568 [ 117.549245] Buffer I/O error on device sdb1, logical block 22569 <3> [ 117.809462] sd 6:0:0:0: [sdb] No Caching mode page found [ 117.809470] sd 6:0:0:0: [sdb] Assuming drive cache: write through [ 117.812696] sd 6:0:0:0: [sdb] No Caching mode page found [ 117.812703] sd 6:0:0:0: [sdb] Assuming drive cache: write through [ 117.813688] sdb: sdb1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
