Return-Path: Message-ID: <532B25FC.3070408@hurleysoftware.com> Date: Thu, 20 Mar 2014 13:31:40 -0400 From: Peter Hurley MIME-Version: 1.0 To: balbi@ti.com, Marcel Holtmann CC: Alan Cox , Greg KH , Muralidharan Karicheri , linux-bluetooth@vger.kernel.org, linux-serial@vger.kernel.org, Linux Kernel Mailing List , Huang Shijie Subject: Re: hci_ldsic nested locking problem References: <20140320163435.GH32692@saruman.home> <1395333736.22077.32.camel@acox1-desk.ger.corp.intel.com> <20140320171621.GA2827@saruman.home> In-Reply-To: <20140320171621.GA2827@saruman.home> Content-Type: text/plain; charset=UTF-8; format=flowed List-ID: [ +cc Huang Shijie ] On 03/20/2014 01:16 PM, Felipe Balbi wrote: > On Thu, Mar 20, 2014 at 04:42:16PM +0000, Alan Cox wrote: >> On Thu, 2014-03-20 at 11:34 -0500, Felipe Balbi wrote: >>> Hi, >>> >>> when 8250 driver calls uart_write_wakeup(), the tty port lock is already >>> taken. hci_ldisc.c's implementation of ->write_wakeup() calls >>> tty->ops->write() to actually send the characters, but that call will >>> try to acquire the same port lock again. >>> >>> Looking at other line disciplines that looks like a bug in hci_ldisc.c. >>> Am I correct to assume that ->write_wakeup() is supposed to *just* >>> wakeup the bottom half so we handle ->write() in another context ? >>> >>> Is it legal to call tty->ops->write() from within ->write_wakeup() ? >> >> It isn't because you might send all the bytes and go >> >> write >> write_wakeup >> write >> write wakeup >> ... >> >> and recurse > > cool, so there really is a bug in hci_ldisc. Marcel, any tips on how do > you want this to be sorted out ? hci_uart_tx_wakeup() should perform the I/O as work. FWIW, this was reported by Huang Shijie back on Dec 6. I'd fix it but I have no way to test it. Regards, Peter Hurley