From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Marcel Holtmann To: BlueZ development In-Reply-To: <451426AA.7080700@verizon.net> References: <451426AA.7080700@verizon.net> Date: Mon, 25 Sep 2006 23:40:16 +0200 Message-Id: <1159220416.20997.11.camel@localhost> Mime-Version: 1.0 Subject: Re: [Bluez-devel] race condition in hci_usb.c? Reply-To: BlueZ development List-Id: BlueZ development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Sender: bluez-devel-bounces@lists.sourceforge.net Errors-To: bluez-devel-bounces@lists.sourceforge.net Hi Jose, > I'm studying the hci_usb driver and I found a possible race condition. > The routine hci_usb_tx_wakeup is called from hci_sub_send_frame > and from hci_usb_tx_complete to get some work done by calling > hci_usb_tx_process. It basically provides serial access to > hci_usb_tx_process by using a couble of bit variables: > HCI_USB_TX_PROCESS and HCI_USB_TX_WAKEPUP. > > The problem is that if hci_usb_tx_wakeup is invoked again from a > different context while execution is just terminating hci_usb_tx_process > (right after the while loop), then hci_usb_tx_process will miss the > wakeup. This condition will correct itself when another call is made > to hci_usb_send_frame or another urb finishes transmission. > > I experimented by replacing hci_usb_tx_wakeup with a tasklet > that schedules hci_usb_tx_process. This to me seems like a safer > approach. feel free to provide a patch. In general the hci_usb driver needs a complete rewrite anyway. Regards Marcel ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Bluez-devel mailing list Bluez-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bluez-devel