Hi Paul, On Mon, 26 Jun 2006 19:49:09 -0500 Paul Fulghum <[EMAIL PROTECTED]> wrote:
| On Mon, 2006-06-26 at 15:26 -0700, Greg KH wrote: | > On Fri, Jun 23, 2006 at 02:28:42PM -0300, Luiz Fernando N. Capitulino wrote: | > > On Thu, 22 Jun 2006 09:29:40 +0100 | > > Russell King <[EMAIL PROTECTED]> wrote: | > > | > > | | > > | Consider this scenario with what you're proposing: | > > | | > > | thread irq | > > | | > > | take mutex | > > | get_mctrl | > > | cts changes state | > > | take port lock | > > | mctrl state read | > > | tty->hw_stopped changed state | > > | release port lock | > > | releaes mutex | > > | take port lock | > > | update tty->hw_stopped | > > | release port lock | > > | | > > | Now, tty->hw_stopped does not reflect the hardware state, which will be | > > | buggy and can cause a loss of transmission. | > > | | > > | I'm not sure what to suggest on this one since for USB drivers you do | > > | need to be able to sleep in this method... but for UARTs you must not. | | What about this ugly fragment? | (assuming get_mctrl not called from IRQ) What's the problem with get_mctrl() being called from IRQ? Note that get_mctrl() is a callback and the driver is free to call _its_ get_mctrl() from IRQ if it wants to. | take mutex | take port lock | again: | save local copy of icount | release port lock | get_mctrl | take port lock | if (icount changed) | goto again | update tty->hw_stopped | release port lock | release mutex Well, I think it'd work. But how can we keep track of 'icount'? Should the driver add 1 if it updates 'tty->hw_stopped'? PS: Sorry for the long delay, I was off last week. -- Luiz Fernando N. Capitulino Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
