Messages in this thread | | | Date | Thu, 19 Sep 2013 06:43:16 -0400 | From | Peter Hurley <> | Subject | Re: [PATCH net 1/3] slip/slcan: added locking in wakeup function |
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[ +cc Greg Kroah-Hartman]
On 09/19/2013 06:35 AM, Marc Kleine-Budde wrote: > On 09/19/2013 12:29 PM, Andre Naujoks wrote: >> On 19.09.2013 11:36, schrieb Marc Kleine-Budde: >>> On 09/13/2013 07:37 PM, Andre Naujoks wrote: >>>> The locking is needed, since the the internal buffer for the CAN >>>> frames is changed during the wakeup call. This could cause buffer >>>> inconsistencies under high loads, especially for the outgoing >>>> short CAN packet skbuffs. >>>> >>>> The needed locks led to deadlocks before commit >>>> "5ede52538ee2b2202d9dff5b06c33bfde421e6e4 tty: Remove extra >>>> wakeup from pty write() path", which removed the direct callback >>>> to the wakeup function from the tty layer. >>> >>> What does that mean for older kernels? (< >>> 5ede52538ee2b2202d9dff5b06c33bfde421e6e4) >> >> It seems the slcan (and slip) driver is broken for older kernels. See >> this thread for a discussion about the patch in pty.c. >> >> http://marc.info/?l=linux-kernel&m=137269017002789&w=2 > > Thanks for the info. > >> The patch from Peter Hurley was actually already in the queue, when I >> ran into the problem, and is now in kernel 3.12. >> >> Without the pty patch and slow CAN traffic, the driver works, because >> the wakeup is called directly from the pty driver. That is also the >> reason why there was no locking. It would just deadlock. >> >> When the pty driver defers the wakeup, we ran into synchronisation >> problems (which should be fixed by the locking) and eventually into a >> kernel panic because of a recursive loop (which should be fixed by the >> pty.c patch). >> >> Maybe it is possible to get both patches back into the stable branches? > > Sounds reasonable. You might get in touch with Peter Hurley, if his > patch is scheduled for stable. Documentation/stable_kernel_rules.txt > suggests a procedure if your patch depends on others to be cherry picked.
Already following along.
I'd like to wait for 3.12 release before the pty patch goes to -stable (so that it gets more in-the-wild testing).
Regards, Peter Hurley
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