On 29/10/12 06:14 PM, Alan Stern wrote:
On Mon, 29 Oct 2012, Richard Retanubun wrote:
Focusing down on one of the dumps:
unreferenced object 0xd3849740 (size 8):
comm "khubd", pid 1026, jiffies 232553037 (age 506.597s)
hex dump (first 8 bytes):
4d 43 38 37 30 35 00 00 MC8705..
backtrace:
[<e30efd74>] usb_cache_string+0x74/0xac [usbcore]
[<e30e77bc>] usb_enumerate_device+0x44/0xf8 [usbcore]
[<e30e7aa0>] usb_new_device+0x3c/0x13c [usbcore]
[<e30e9824>] hub_thread+0xc8c/0x1544 [usbcore]
[<c0043aa8>] kthread+0x7c/0x80
[<c000ed48>] kernel_thread+0x4c/0x68
I have a small question. How does the memory kmalloc-ed() in usb_cache_string is supposed to be released?
(during usb_serial_disconnect()?)
It doesn't get released during usb_serial_disconnect(). It gets
released during usb_release_dev() in drivers/usb/core/usb.c.
Is the sierra driver is supposed to participate
in the tear down process (in sierra_release() maybe) and not doing something that is expected?
Probably not.
I am still missing the link between the actions done by the hub_thread() for the caching the stings
and the sierra driver code.
They aren't all that closely related.
usb_release_dev() won't be called until all references to the USB
device have been dropped. Maybe there's an extra reference hanging
around.
Alan Stern
Thanks a lot for the hint Alan.
I added a dev_dbg print in usb_release_dev() and saw that in the builds where there is a leak, this was simply never called!
the last line printed in a trace with all dev_dbg on is this "usb_disable_device nuking all URBs"
When the sierra modem is unplugged, the cleanup sequence never calls usb_release_dev() (on PL2303 it always calls usb_release_dev()
This is the current state of versions from linux-stable
3.0.y (3.0.51) - Have the issue
3.2.y (3.2.33) - Have the issue
3.4.y (3.4.18) - Have the issue
3.5.y (3.5.7) - Does not have the issue (but leaks because the portdata patches is not backported yet)
3.6.y (3.6.6) - Does not have the issue
So a diff between 3.4.y and 3.5.y ought to narrow it down further.
I am posting just in case someone recalls a particular patch I should be trying out first...
-- RR --
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