Messages in this thread | | | Date | Mon, 24 May 2004 13:06:11 -0700 | From | Greg KH <> | Subject | Re: [linux-usb-devel] [PATCH] visor: Fix Oops on disconnect |
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On Mon, May 24, 2004 at 03:38:58PM -0400, nardelli wrote: > nardelli wrote: > > > >One more question - my system does not really like it when I redirect > >/dev/urandom > >to either the first or second port. I know that it obviosuly makes no > >sense to > >do such a thing, but is it expected that there should be no problems > >associated > >with this. I'm not finished testing, so I'm not sure how severe a problem > >develops. > >I'll report in when I know more about this. > > > > Here's some preliminary info: > > 1) Whether writing to the 1st or 2nd port, the machine hangs pretty badly > after catting /dev/urandom for more than 1 second or two. This continues > even after catting has stopped, and the device has been disconnected. This > smells like some type of resource leak, probably memory, to me.
Which machine dies? The pilot or the Linux box?
> 2) I've included an Oops when writing to the 1st serial port, showing some > difficulty allocating memory.
So we ran out of memory? Not good.
> 3) After looking at visor_write(), I was a bit surprised to see it > allocating its own urb and buffer, while I thought it would be using > the ones that were allocated in usb-serial.usb_serial_probe(). After > looking at other serial devices that use usb_submit_urb() in their > write() functions, I found that the following used the buffers/urb > allocated for them: > > cyberjack, digi_acceleport, generic, io_ti, ipaq, ir-usb, keyspan_pda, > kobil_sct, mct_u232, omninet, pl2303, safe_serial > > while I found that the following created their own (some for each write): > > empeg, ftdi_sio, keyspan, kl5kusb105, visor, whiteheat > > I'm not so sure about: > io_edgeport
It uses it's own buffers from what I remember.
> Is this expected behavior, or am I just missing something here?
Expected, not all of the usb-serial drivers have to do the same thing, as they operate on very different types of hardware.
> It would seem like reusing the buffer and urb would be advantageous, > but there may be more issues here than I am aware of.
Reusing the buffer and urb is _slow_. The visor driver creates a new buffer for every call to write. It is entirely possible that you can starve the kernel of memory by sending it the output of a raw device node, as that data comes faster than the USB data can be sent.
But this is a different problem from the one you originally set out to fix, how about sending a new patch for the treo disconnect problem, and then we can work on the next issues.
thanks,
greg k-h - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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