Thanks for information Marcel. Do you know that 2.6.33-rc6 kernel code having any change regarding points I encountered on older release? Regards, Dev -----Original Message----- From: Marcel Holtmann [mailto:marcel@xxxxxxxxxxxx] Sent: Thursday, February 04, 2010 7:41 PM To: SINGH DEVENDRA-DHGW76 Cc: linux-bluetooth@xxxxxxxxxxxxxxx Subject: RE: Kernel panic when SCO connection Hi, > I noticed the same problem when I was working with a embedded board > with Broadcom chipset and Linux kernel 2.6.18 (I guess). Use case was, > a Bluetooth based headset sends data to the CSR Bluetooth dongle(USB), > which in turn provide data to the Application through bluez stack. > > > Following were my observation: > > 1. Board processor is not strong enough and so there was no URB in the > queue and audio data was getting accumulated in the USB host controller. > There are only 2 Rx URBs (hci_usb.h: #define HCI_MAX_ISOC_RX 2). > 2. Actual length of data for data in the URB is reaching to the level > of 1K bytes. (Max ISOC data length) however Bluetooth driver is > expecting 10 packets of 64 bytes each. hci_usb_isoc_rx_submit function > in hci_usb.c file. > 3. Completion routine copies data for actual length returned for > packet that could be 1024 while limit for one packet is 64B only. (hci_usb.c: > hci_usb_rx_complete function). > 4. These "SCO packet for unknown connection handle" error logs further > complicated the problem as this will further eat-up cpu time. > > > Cause: > > Max length of available transfer buffer could be 640 bytes (that's > depend upon the buffer index) and copying big chunk of data was > resulting into memory overrun and kernel memory was getting corrupted > that results in un-expected behavior line connection break, lots of > noise and even kernel panic some times. > > > Following was the work around: > > 1. Increased number of Rx URBs to 6. (hci_usb.h: #define > HCI_MAX_ISOC_RX 6). > 2. Increased transfer buffer size to 1.5K. > 3. Put a check in completion routine that in case actual length is > more then frame length then copy only frame length size data as follows: > > int len = (urb->iso_frame_desc[i].actual_length > > urb->iso_frame_desc[i].length)? > urb->iso_frame_desc[i].length: > urb->iso_frame_desc[i].actual_length; > > __recv_frame(husb, > _urb->type, > urb->transfer_buffer + urb->iso_frame_desc[i].offset, > len); > 4. Logging "SCO packet for unknown connection handle" error only once > for 100 errors. This will give more change to queue a URB as > follows(hci_core.c:hci_scodata_packet function): > hdev->stat.err_rx++; > if(!(hdev->stat.err_rx % 100)) > { > BT_ERR("%s 100 SCO packets for unknown connection > handles",hdev->name); } > > > I must say that I did not try with latest Linux kernel however I could > not see any code change regarding this functionality. Hope this will > help. I can see a big code change in the latest 2.6.33-rc6 kernel. The hci_usb driver has been replaced by btusb since a few releases now ;) Regards Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
