Messages in this thread | | | Date | Sun, 24 Nov 2013 22:28:15 +0100 | From | Daniel Lezcano <> | Subject | Re: [PATCH] clocksource: Do not drop unheld reference on device node |
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On 11/22/2013 08:22 PM, Uwe Kleine-König wrote: > On Fri, Nov 22, 2013 at 05:31:46PM +0100, Daniel Lezcano wrote: >> On 11/22/2013 05:16 PM, Thierry Reding wrote: >>> On Sat, Oct 19, 2013 at 12:49:48AM +0200, Thierry Reding wrote: >>>> When booting a recent kernel on ARM with OF_DYNAMIC enabled, the kernel >>>> warns about the following: >>>> >>>> [ 0.000000] ERROR: Bad of_node_put() on /timer@50004600 >>>> [ 0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.12.0-rc5-next-20131017-00077-gedfd827-dirty #406 >>>> [ 0.000000] [<c0015b68>] (unwind_backtrace+0x0/0xf4) from [<c00117e4>] (show_stack+0x10/0x14) >>>> [ 0.000000] [<c00117e4>] (show_stack+0x10/0x14) from [<c055f734>] (dump_stack+0x9c/0xc8) >>>> [ 0.000000] [<c055f734>] (dump_stack+0x9c/0xc8) from [<c03b47d4>] (of_node_release+0x90/0x9c) >>>> [ 0.000000] [<c03b47d4>] (of_node_release+0x90/0x9c) from [<c03b5084>] (of_find_matching_node_and_match+0x78/0xb4) >>>> [ 0.000000] [<c03b5084>] (of_find_matching_node_and_match+0x78/0xb4) from [<c07887c8>] (clocksource_of_init+0x60/0x70) >>>> [ 0.000000] [<c07887c8>] (clocksource_of_init+0x60/0x70) from [<c076e99c>] (start_kernel+0x1f4/0x33c) >>>> [ 0.000000] [<c076e99c>] (start_kernel+0x1f4/0x33c) from [<80008074>] (0x80008074) >>>> >>>> This is caused by clocksource_of_init() dropping a reference on the >>>> device node that it never took. The reference taken by the loop is >>>> implicitly dropped on subsequent iterations. See the implementation of >>>> and the comment on top of the of_find_matching_node_and_match() >>>> function for reference (no pun intended). > I only saw the end of the comment saying: > > Returns a node pointer with refcount incremented, use > of_node_put() on it when done. > > Maybe that could be improved to something like: > > /** > * of_find_matching_node_and_match - Find a node based on an of_device_id > * match table > * @from: The node to start searching from or NULL, the node you pass > * will not be searched, only the next one will; typically, you > * pass what the previous call returned. > * @matches: ... > * @match: ... > * > * Reference counting: Puts a reference on @from and increases the > * reference count of the returned node. > */ > >>>> >>>> Signed-off-by: Thierry Reding <treding@nvidia.com> >>>> --- >>>> drivers/clocksource/clksrc-of.c | 1 - >>>> 1 file changed, 1 deletion(-) >>> >>> Can someone look at this? >> >> Yes. Sounds like I missed it. >> >> This regression has been introduced by: >> >> commit 326e31eebe61dc838e031ea16968b2cfb43443e3 >> Author: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> >> Date: Tue Oct 1 11:00:53 2013 +0200 >> >> clocksource: Put nodes passed to CLOCKSOURCE_OF_DECLARE >> callbacks centrally >> >> Instead of letting each driver call of_node_put do it centrally in the >> loop that also calls the CLOCKSOURCE_OF_DECLARE callbacks. This is less >> prone to error and also moves getting and putting the references >> into the >> same function. >> >> Consequently all respective of_node_put calls in drivers are removed. >> >> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> >> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> >> Acked-by: David Brown <davidb@codeaurora.org> > Still all but the hook in clocksource_of_init of this commit was > correct, right? (Well, but this buggy hunk makes the commit log wrong.)
I don't understand your comment, can you elaborate ?
Thanks -- Daniel
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