dma-buf implicitly track their (DMA) rendering using a reservation_object, which tracks ether the last write (in an exclusive fence) or the current renders (with a set of shared fences). To wait upon a reservation object in conjunction with other sources, kfence_add_reservation() extracts the DMA fences from the object and adds the individual waits for the kfence.

Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Shuah Khan shuahkh@osg.samsung.com Cc: Tejun Heo tj@kernel.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Andrew Morton akpm@linux-foundation.org Cc: Ingo Molnar mingo@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Thomas Gleixner tglx@linutronix.de Cc: "Paul E. McKenney" paulmck@linux.vnet.ibm.com Cc: Dan Williams dan.j.williams@intel.com Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Davidlohr Bueso dave@stgolabs.net Cc: Nikolay Aleksandrov nikolay@cumulusnetworks.com Cc: "David S. Miller" davem@davemloft.net Cc: "Peter Zijlstra (Intel)" peterz@infradead.org Cc: Rasmus Villemoes linux@rasmusvillemoes.dk Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Alexander Potapenko glider@google.com Cc: linux-kernel@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org --- include/linux/kfence.h | 5 ++++ kernel/async.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++---- 2 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/include/linux/kfence.h b/include/linux/kfence.h index 1abec5e6b23c..2f01eb052e4d 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -17,6 +17,7 @@ struct completion; struct fence; enum hrtimer_mode; +struct reservation_object;

struct kfence { wait_queue_head_t wait; @@ -34,6 +35,10 @@ extern int kfence_add_completion(struct kfence *fence, extern int kfence_add_dma(struct kfence *fence, struct fence *dma, gfp_t gfp); +extern int kfence_add_reservation(struct kfence *fence, + struct reservation_object *resv, + bool write, + gfp_t gfp); extern int kfence_add_delay(struct kfence *fence, clockid_t clock, enum hrtimer_mode mode, ktime_t delay, u64 slack, diff --git a/kernel/async.c b/kernel/async.c index 5d02445e36b7..1fa1f39b5a74 100644 --- a/kernel/async.c +++ b/kernel/async.c @@ -54,9 +54,10 @@ asynchronous and synchronous parts of the kernel. #include <linux/kfence.h> #include <linux/ktime.h> #include <linux/export.h> -#include <linux/wait.h> +#include <linux/reservation.h> #include <linux/sched.h> #include <linux/slab.h> +#include <linux/wait.h> #include <linux/workqueue.h>

#include "workqueue_internal.h" @@ -123,11 +124,17 @@ static atomic_t entry_count; * allowing multiple pending / signals to be sent before the kfence is * complete. * - * kfence_add() / kfence_add_completion() / kfence_add_dma() + * kfence_add() / kfence_add_completion() + * / kfence_add_dma() + * + * sets the kfence to wait upon another fence or completion respectively. To + * wait upon DMA activity, either use * - * sets the kfence to wait upon another fence, completion, or DMA fence - * respectively. To set the fence to wait for at least a certain period of - * time, or until after a certain point in time, use + * kfence_add_dma() or kfence_add_reservation() + * + * depending on the manner of DMA activity tracking. To set the fence to wait + * for at least a certain period of time, or until after a certain point in + * time, use * * kfence_add_timer() * @@ -547,6 +554,54 @@ int kfence_add_dma(struct kfence *fence, struct fence *dma, gfp_t gfp) EXPORT_SYMBOL_GPL(kfence_add_dma);

/** + * kfence_add_reservation - set the fence to wait upon a reservation_object + * @fence: this kfence + * @resv: target reservation_object (collection of DMA fences) to wait upon + * @write: Wait for read or read/write access + * @gfp: the allowed allocation type + * + * kfence_add_reservation() causes the @fence to wait upon completion of the + * reservation object (a collection of DMA fences), either for read access + * or for read/write access. + * + * Returns 1 if the @fence was successfully to the waitqueues of @resv, 0 + * if @resev was already signaled (and so not added), or a negative error code. + */ +int kfence_add_reservation(struct kfence *fence, + struct reservation_object *resv, + bool write, + gfp_t gfp) +{ + struct fence *excl, **shared; + unsigned count, i; + int ret; + + ret = reservation_object_get_fences_rcu(resv, &excl, &count, &shared); + if (ret) + return ret; + + if (write) { + for (i = 0; i < count; i++) { + ret |= kfence_add_dma(fence, shared[i], gfp); + if (ret < 0) + goto out; + } + } + + if (excl) + ret |= kfence_add_dma(fence, excl, gfp); + +out: + fence_put(excl); + for (i = 0; i < count; i++) + fence_put(shared[i]); + kfree(shared); + + return ret; +} +EXPORT_SYMBOL_GPL(kfence_add_reservation); + +/** * kfence_add_delay - set the fence to wait for a period of time * @fence: this kfence * @clock: which clock to program