Messages in this thread | | | Date | Thu, 7 May 2009 17:23:16 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] Detect and warn on atomic_inc/atomic_dec wrapping around |
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On Thu, 30 Apr 2009 19:39:50 +0530 Nikanth Karthikesan <knikanth@novell.com> wrote:
> > 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. > > > ... > > --- a/include/asm-generic/atomic.h > +++ b/include/asm-generic/atomic.h > @@ -4,15 +4,51 @@ > * Copyright (C) 2005 Silicon Graphics, Inc. > * Christoph Lameter > * > - * Allows to provide arch independent atomic definitions without the need to > - * edit all arch specific atomic.h files. > */ > > +#include <linux/kernel.h> > #include <asm/types.h> > +#include <asm/bug.h>
We're going to have real trouble making changes like this to a low-level header file - sparc64 results below.
> +/** > + * atomic_inc - increment atomic variable > + * @v: pointer of type atomic_t > + * > + * Atomically increments @v by 1. > + */ > +static inline void atomic_inc(atomic_t *v) > +{ > +#ifdef CONFIG_ENABLE_WARN_ATOMIC_INC_WRAP > + WARN_ONCE((atomic_read(v) > (INT_MAX / 2)), > + KERN_ERR "atomic inc overflow!"); > +#endif > + raw_atomic_inc(v); > +}
Are we allowed to assume that atomic_inc==raw_atomic_inc for all architectures which use this definition?
Do we know that atomic_read() is defined at this point?
We can avoid the problematic includes via
extern void atomic_inc_screwed_up(atomic_t *v);
static inline void atomic_inc(atomic_t *v) { #ifdef CONFIG_ENABLE_WARN_ATOMIC_INC_WRAP if (atomic_read(v) > (INT_MAX / 2)) atomic_inc_screwed_up(v); #endif raw_atomic_inc(v); }
In file included from /usr/src/devel/arch/sparc/include/asm/atomic_64.h:117, from /usr/src/devel/arch/sparc/include/asm/atomic.h:4, from include/linux/debug_locks.h:5, from include/linux/lockdep.h:19, from include/linux/spinlock_types.h:18, from include/linux/spinlock.h:80, from include/linux/seqlock.h:29, from include/linux/time.h:8, from include/linux/timex.h:56, from include/linux/sched.h:54, from arch/sparc/kernel/asm-offsets.c:13: include/asm-generic/atomic.h:20: error: syntax error before numeric constant include/asm-generic/atomic.h:21: warning: static declaration of 'atomic_add' follows non-static declaration /usr/src/devel/arch/sparc/include/asm/atomic_64.h:22: warning: previous declaration of 'atomic_add' was here include/asm-generic/atomic.h: In function `atomic_add': include/asm-generic/atomic.h:21: error: number of arguments doesn't match prototype /usr/src/devel/arch/sparc/include/asm/atomic_64.h:22: error: prototype declaration include/asm-generic/atomic.h:26: error: implicit declaration of function `raw_atomic_inc' include/asm-generic/atomic.h:26: error: `v' undeclared (first use in this function) include/asm-generic/atomic.h:26: error: (Each undeclared identifier is reported only once include/asm-generic/atomic.h:26: error: for each function it appears in.) include/asm-generic/atomic.h: At top level: include/asm-generic/atomic.h:35: error: syntax error before numeric constant include/asm-generic/atomic.h:36: warning: static declaration of 'atomic_sub' follows non-static declaration /usr/src/devel/arch/sparc/include/asm/atomic_64.h:24: warning: previous declaration of 'atomic_sub' was here include/asm-generic/atomic.h: In function `atomic_sub': include/asm-generic/atomic.h:36: error: number of arguments doesn't match prototype /usr/src/devel/arch/sparc/include/asm/atomic_64.h:24: error: prototype declaration include/asm-generic/atomic.h:41: error: implicit declaration of function `raw_atomic_dec' include/asm-generic/atomic.h:41: error: `v' undeclared (first use in this function)
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