Re: lockdep oddity

Heiko Carstens
2006-09-06T11:59:14Z

> > Found this will debugging some random memory corruptions that happen when
> > CONFIG_PROVE_LOCKING and CONFIG_PROFILE_LIKELY are both on.
> > Switching both off or having only one of them on seems to work.
> There's potential for a some issues in current -mm , given the config
> above. If you us the generic atomic operations
> (asm-generic/bitops/atomic.h) for test_and_set_bit(). It eventually
> calls into trace_hardirqs_off() and then back into likely profiling.

Your patch has this in it too:

/*
* We check for constant values with __builtin_constant_p() since
* it's not interesting to profile them, and there is a compiler
* bug in gcc 3.x which blows up during constant evalution when
* CONFIG_PROFILE_LIKELY is turned on.
*/
#define likely(x) (__builtin_constant_p(x) ? (!!(x)) : __check_likely((x), 1))
#define unlikely(x) (__builtin_constant_p(x) ? (!!(x)) : __check_likely((x), 0))

Could you define "blows up"? My reading of the text above is: "this code
below makes sure it does work with gcc 3.x as well".
Now I used gcc 3.4.1 and get random memory corruptions while with gcc 4.1.1
everything seems to be ok....