On Tue, Feb 20, 2018 at 03:49:46PM +0100, Christian König wrote:
> amdgpu needs to verify if userspace sends us valid addresses and the simplest
> way of doing this is to check if the buffer object is locked with the ticket
> of the current submission.
>
> Clean up the access to the ww_mutex internals by providing a function
> for this and extend the check to the thread owning the underlying mutex.
>
> v2: split amdgpu changes into separate patch as suggested by Alex
> v3: change logic as suggested by Daniel
> v4: fix test in case ctx is NULL
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> ---
> include/linux/ww_mutex.h | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
> index 39fda195bf78..fea4acc0bcbc 100644
> --- a/include/linux/ww_mutex.h
> +++ b/include/linux/ww_mutex.h
> @@ -358,4 +358,23 @@ static inline bool ww_mutex_is_locked(struct ww_mutex *lock)
> return mutex_is_locked(&lock->base);
> }
>
> +/**
> + * ww_mutex_is_owned_by - is the w/w mutex locked by this task in that context
> + * @lock: the mutex to be queried
> + * @ctx: the w/w acquire context to test
> + *
> + * If @ctx is not NULL test if the mutex is owned by this context.
> + * If @ctx is NULL test if the mutex is owned by the current thread and not
> + * locked in any context.
Ok I think with the increased guarantees this needs a better kerneldoc, I
think we need to at least add ".... and not locked in any context, i.e.
acquired using either ww_mutex_trylock() or ww_mutex_lock() without
supplying a &ww_acquire_ctx."
I think with that we have a nice 1:1 mapping between the context you
supply to the ww_mutex_lock function and to this one. That means generic
code which takes a ctx (but can handle NULL) should dtrt no matter what.
With the kerneldoc augmented:
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
I'll probably regret this r-b too, but hey to err is human :-)
Cheers, Daniel
> + */
> +static inline bool ww_mutex_is_owned_by(struct ww_mutex *lock,
> + struct ww_acquire_ctx *ctx)
> +{
> + if (ctx)
> + return likely(READ_ONCE(lock->ctx) == ctx);
> +
> + return likely(__mutex_owner(&lock->base) == current) &&
> + likely(READ_ONCE(lock->ctx) == NULL;
> +}
> +
> #endif
> --
> 2.14.1
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
