Messages in this thread | | | From | Nikanth Karthikesan <> | Subject | Re: [PATCH] Detect and warn on atomic_inc/atomic_dec wrapping around | Date | Fri, 1 May 2009 10:27:46 +0530 |
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On Friday 01 May 2009 03:15:26 Andrew Morton wrote: > On Thu, 30 Apr 2009 19:39:50 +0530 > Nikanth Karthikesan <knikanth@novell.com> wrote: > > > > If I had a dollar for each wordwrapped patch I get sent... >
Ah..very sorry, was a bit hasty. Would pay it, when I get to meet you. ;-)
> > Detect and warn on atomic_inc/atomic_dec overflow. > > > > Add a debug option to detect and warn when the 32-bit atomic_t overflows > > during atomic_inc and atomic_dec. > > OK. > > I'll beef the changelog up a bit - this one is wimpy. >
Thanks.
> The question is: do we put this in mainline? I guess we might as well > give it a shot. It may well find bugs and it might also trigger false > positives. We can then fix the bugs and decide whether the false > positives warrant reverting it again, all very easy. > > > +#include <asm/bug.h> > > checkpatch says > > WARNING: Use #include <linux/bug.h> instead of <asm/bug.h> > #215: FILE: include/asm-generic/atomic.h:11: > +#include <asm/bug.h> > > Was this an oversight, or did you try using linux/bug.h and discovered > some problem?
I tried with linux/bug.h. But it creates a cyclic dependency. linux/bug.h pulls in linux/module.h => linux/spinlock.h => asm/spinlock.h (which uses atomic_inc) => asm/atomic.h,.
> > > index 812c282..773c1a4 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -17,6 +17,17 @@ config ENABLE_WARN_DEPRECATED > > Disable this to suppress the "warning: 'foo' is deprecated > > (declared at kernel/power/somefile.c:1234)" messages. > > > > +config HAVE_ARCH_DEBUG_ATOMIC > > + bool > > + > > +config ENABLE_WARN_ATOMIC_INC_WRAP > > + bool "Enable warning on atomic_inc()/atomic_dec() wrap" > > + depends on HAVE_ARCH_DEBUG_ATOMIC > > + default y > > + help > > + Enable printing a warning when atomic_inc() or atomic_dec() > > + operation wraps around the 32-bit value. > > + > > Yes, I agree with `default y' for now. But we might want to turn it > off again later. Adding that WARN to every atomic_inc/atomic_dec site > must do terrible things to the kernel text footprint. > > Of course, if we make if `default y' for a while and then switch it to > `default n', the `y' state will linger for a very long time in all the > kernel developers' .configs. Good! Very sneaky.
:)
Thanks Nikanth
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