A common requirement when scheduling a task is that it should be not be begun until a certain point in time is passed (e.g. queue_delayed_work()). kfence_await_hrtimer() causes the kfence to asynchronously wait until after the appropriate time before being woken.

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/kfence.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++ lib/test-kfence.c | 44 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 107 insertions(+)

diff --git a/include/linux/kfence.h b/include/linux/kfence.h index 6e32385b3b8c..76a2f95dfb70 100644 --- a/include/linux/kfence.h +++ b/include/linux/kfence.h @@ -16,6 +16,7 @@ #include <linux/wait.h>

struct completion; +enum hrtimer_mode;

struct kfence { wait_queue_head_t wait; @@ -43,6 +44,10 @@ int kfence_await_kfence(struct kfence *fence, int kfence_await_completion(struct kfence *fence, struct completion *x, gfp_t gfp); +int kfence_await_hrtimer(struct kfence *fence, + clockid_t clock, enum hrtimer_mode mode, + ktime_t delay, u64 slack, + gfp_t gfp); void kfence_complete(struct kfence *fence); void kfence_wake_up_all(struct kfence *fence); void kfence_wait(struct kfence *fence); diff --git a/kernel/kfence.c b/kernel/kfence.c index 693af9da545a..59c27910a749 100644 --- a/kernel/kfence.c +++ b/kernel/kfence.c @@ -48,6 +48,9 @@ * - kfence_await_completion(): the kfence asynchronously waits upon a * completion * + * - kfence_await_hrtimer(): the kfence asynchronously wait for an expiration + * of a timer + * * A kfence is initialised using kfence_init(), and starts off awaiting an * event. Once you have finished setting up the fence, including adding * all of its asynchronous waits, call kfence_complete(). @@ -429,3 +432,58 @@ int kfence_await_completion(struct kfence *fence, return pending; } EXPORT_SYMBOL_GPL(kfence_await_completion); + +struct timer_cb { + struct hrtimer timer; + struct kfence *fence; +}; + +static enum hrtimer_restart +timer_kfence_wake(struct hrtimer *timer) +{ + struct timer_cb *cb = container_of(timer, typeof(*cb), timer); + + kfence_complete(cb->fence); + kfence_put(cb->fence); + kfree(cb); + + return HRTIMER_NORESTART; +} + +/** + * kfence_await_hrtimer - set the fence to wait for a period of time + * @fence: this kfence + * @clock: which clock to program + * @mode: delay given as relative or absolute + * @delay: how long or until what time to wait + * @slack: how much slack that may be applied to the delay + * + * kfence_await_hrtimer() causes the @fence to wait for a a period of time, or + * until a certain point in time. It is a convenience wrapper around + * hrtimer_start_range_ns(). For more details on @clock, @mode, @delay and + * @slack please consult the hrtimer documentation. + * + * Returns 1 if the delay was sucessfuly added to the @fence, or a negative + * error code on failure. + */ +int kfence_await_hrtimer(struct kfence *fence, + clockid_t clock, enum hrtimer_mode mode, + ktime_t delay, u64 slack, + gfp_t gfp) +{ + struct timer_cb *cb; + + cb = kmalloc(sizeof(*cb), gfp); + if (!cb) + return -ENOMEM; + + cb->fence = kfence_get(fence); + kfence_await(fence); + + hrtimer_init(&cb->timer, clock, mode); + cb->timer.function = timer_kfence_wake; + + hrtimer_start_range_ns(&cb->timer, delay, slack, mode); + return 1; +} +EXPORT_SYMBOL_GPL(kfence_await_hrtimer); diff --git a/lib/test-kfence.c b/lib/test-kfence.c index b40719fce967..1b0853fda7c3 100644 --- a/lib/test-kfence.c +++ b/lib/test-kfence.c @@ -352,6 +352,44 @@ static int __init test_completion(void) return 0; }

+static int __init test_delay(void) +{ + struct kfence *fence; + ktime_t delay; + int ret; + + /* Test use of a hrtimer as an event source for kfences */ + pr_debug("%s\n", __func__); + + fence = alloc_kfence(); + if (!fence) + return -ENOMEM; + + delay = ktime_get(); + + ret = kfence_await_hrtimer(fence, CLOCK_MONOTONIC, HRTIMER_MODE_REL, + ms_to_ktime(1), 1 << 10, + GFP_KERNEL); + if (ret < 0) + return ret; + if (ret == 0) + return -EINVAL; + + kfence_complete(fence); + kfence_wait(fence); + + delay = ktime_sub(ktime_get(), delay); + kfence_put(fence); + + if (!ktime_to_ms(delay)) { + pr_err("kfence woke too early, delay was only %lldns\n", + (long long)ktime_to_ns(delay)); + return -EINVAL; + } + + return 0; +} + struct task_ipc { struct work_struct work; struct completion started; @@ -522,6 +560,12 @@ static int __init test_kfence_init(void) return ret; }

+ ret = test_delay(); + if (ret < 0) { + pr_err("delay failed\n"); + return ret; + } + return 0; }