On Fri, Jul 06, 2007 at 12:29:27PM -0700, Josh Triplett wrote: > The existing context annotations should suffice for many cases. > compiler.h will need new wrappers for cases like requiring a lock. For > a very simple example: > > compiler.h: > #define require_context(x) __attribute__((context(x,1,1)) > > magic_device.c: > DEFINE_SPINLOCK(device_lock); > struct the_device the_device require_context(device_lock); *ugh* More ugly syntax... > compiler.h: > #ifdef __CHECKER__ > #define fake_context(x) extern const int x > #else > #define fake_context(x) > #endif > > preempt.h: > fake_context(preemption); > #define preempt_disable() ... __acquire(preemption) > #define preempt_enable() ... __release(preemption) > #define might_sleep_attr() ... /* something */ Still not expressive enough... Consider e.g. struct foo *lookup_foo(char *s); // lookup by name, return NULL if failed // or pointer to struct foo with ->mutex // held. Caller should unlock. It's legitimate, not particulary rare and AFAICS can't be expressed. > Sparse does not yet enforce all of these conditions. Also, the "at > least this value" semantic for the precondition makes it hard to use > contexts for things like "this blocks" and "may not block in this > context". As I said, it needs work. However, I intend for it to mean > *exactly* the same thing on functions or variables, except that in the > former case it means "when called", and in the latter case it means > "when accessed". In both cases, you can require a context and change > the context. _What_ change in case of objects? > A fine question. In the simple cases, "same symbol" will work fairly > well; certainly better than the current "always equal" comparison. :) > Ideally, however, you want "refers to the same value". Alias analysis > could do a fairly good job of that, I think. Not particulary useful, since for int foo(struct bar *p) __acquires(&p->lock); int bar(struct bar *p) __acquires(&p->lock); you will get false negative in (n ? foo : bar) *and* it will persist even if you go for int foo(struct bar *p) __acquires(p); int bar(struct bar *p) __acquires(p); since you will have different symbols (same name, different scopes) here. - To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
