Re: annotating semaphores.

["Christopher Li" <sparse@chrisli.org>]

On Dec 12, 2007 12:00 PM, Dave Jones <davej@redhat.com> wrote:
> Today I came across a bug in the kernel cpufreq code where
> we were missing a bunch of up_write() calls in error paths
> of a function.
>
> I've been trying to get sparse's context checking to pick up
> on the errors and failing.  The kernel patch below is what I have
> so far, but it seems to report no output whatsoever.
> What am I missing ?

Can you share the example buggy cpufreq code that miss the up_write() calls?

> --- a/lib/rwsem-spinlock.c
> +++ b/lib/rwsem-spinlock.c
> @@ -162,6 +162,7 @@ void fastcall __sched __down_read(struct rw_semaphore *sem)
>
>         tsk->state = TASK_RUNNING;
>   out:
> +       __acquire(sem);
>         ;
>  }

That is not needed. Because the __down_read is not an inline function. The
extern void FASTCALL(__down_read(struct rw_semaphore *sem)) __acquires(sem);
declare should be good enough.

Chris