* module refcnt underflow
@ 2013-06-26 16:20 Lucas De Marchi
2013-07-01 2:38 ` Rusty Russell
0 siblings, 1 reply; 2+ messages in thread
From: Lucas De Marchi @ 2013-06-26 16:20 UTC (permalink / raw)
To: lkml, Rusty Russell, linux-modules
Hi,
While checking somethings for a next release of kmod I noticed this
strange thing:
cat /sys/module/acpi_cpufreq/refcnt
18446744073709551614
We outputs this as "-1" in lsmod because we treat the value as signed.
I was just going to change it to unsigned to make it compatible with
what module-init-tools does but... For me it looks like a bug in the
kernel since in this file we just have the output of
kernel/module.c:module_refcount()
I have this behavior on 3.9.2 but judging by the missing commits in
kernel/module.c, this would also happen in latest head. I've never
seen such a value so I guess it might be difficult to reproduce it
again.
Any hints on what could cause decs to be greater than incs in module_refcount()?
--
Lucas De Marchi
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: module refcnt underflow
2013-06-26 16:20 module refcnt underflow Lucas De Marchi
@ 2013-07-01 2:38 ` Rusty Russell
0 siblings, 0 replies; 2+ messages in thread
From: Rusty Russell @ 2013-07-01 2:38 UTC (permalink / raw)
To: Lucas De Marchi, lkml, linux-modules
Cc: Kent Overstreet, Rafael J. Wysocki, Viresh Kumar, cpufreq,
linux-pm
Lucas De Marchi <lucas.de.marchi@gmail.com> writes:
> Hi,
>
> While checking somethings for a next release of kmod I noticed this
> strange thing:
>
> cat /sys/module/acpi_cpufreq/refcnt
> 18446744073709551614
>
> We outputs this as "-1" in lsmod because we treat the value as signed.
> I was just going to change it to unsigned to make it compatible with
> what module-init-tools does but... For me it looks like a bug in the
> kernel since in this file we just have the output of
> kernel/module.c:module_refcount()
>
> I have this behavior on 3.9.2 but judging by the missing commits in
> kernel/module.c, this would also happen in latest head. I've never
> seen such a value so I guess it might be difficult to reproduce it
> again.
>
> Any hints on what could cause decs to be greater than incs in module_refcount()?
That points to a bug in the cpufreq code.
At a glance, there's nothing obvious, but there are quite a few
reference counts in that code.
Informed people cc'd...
Thanks,
Rusty.
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