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@xxxxxxxxxxxxxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx
---
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;
}
--
2.8.1
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