Hi,
v2 of this series just adds the selftest support. Patch #1 is modified
slightly (bpf.h modified under tools/include) so that the new selftest
compiles properly. I also added suggested-by tag from Artem whom I
forgot to add in the initial upstream post.
-Tero
Add a new flag BPF_F_TIMER_ABS that can be passed to bpf_timer_start()
to start an absolute value timer instead of the default relative value.
This makes the timer expire at an exact point in time, instead of a time
with latencies induced by both the BPF and timer subsystems.
Suggested-by: Artem Bityutskiy <[email protected]>
Signed-off-by: Tero Kristo <[email protected]>
---
v2:
- added suggested by from Artem
- copied the change from include/uapi/linux/bpf.h to tools/include also
include/uapi/linux/bpf.h | 15 +++++++++++++++
kernel/bpf/helpers.c | 11 +++++++++--
tools/include/uapi/linux/bpf.h | 15 +++++++++++++++
3 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 464ca3f01fe7..7f5b71847984 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4951,6 +4951,12 @@ union bpf_attr {
* different maps if key/value layout matches across maps.
* Every bpf_timer_set_callback() can have different callback_fn.
*
+ * *flags* can be one of:
+ *
+ * **BPF_F_TIMER_ABS**
+ * Start the timer in absolute expire value instead of the
+ * default relative one.
+ *
* Return
* 0 on success.
* **-EINVAL** if *timer* was not initialized with bpf_timer_init() earlier
@@ -7050,4 +7056,13 @@ struct bpf_core_relo {
enum bpf_core_relo_kind kind;
};
+/*
+ * Flags to control bpf_timer_start() behaviour.
+ * - BPF_F_TIMER_ABS: Timeout passed is absolute time, by default it is
+ * relative to current time.
+ */
+enum {
+ BPF_F_TIMER_ABS = (1ULL << 0),
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index af30c6cbd65d..924849d89828 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1253,10 +1253,11 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla
{
struct bpf_hrtimer *t;
int ret = 0;
+ enum hrtimer_mode mode;
if (in_nmi())
return -EOPNOTSUPP;
- if (flags)
+ if (flags > BPF_F_TIMER_ABS)
return -EINVAL;
__bpf_spin_lock_irqsave(&timer->lock);
t = timer->timer;
@@ -1264,7 +1265,13 @@ BPF_CALL_3(bpf_timer_start, struct bpf_timer_kern *, timer, u64, nsecs, u64, fla
ret = -EINVAL;
goto out;
}
- hrtimer_start(&t->timer, ns_to_ktime(nsecs), HRTIMER_MODE_REL_SOFT);
+
+ if (flags & BPF_F_TIMER_ABS)
+ mode = HRTIMER_MODE_ABS_SOFT;
+ else
+ mode = HRTIMER_MODE_REL_SOFT;
+
+ hrtimer_start(&t->timer, ns_to_ktime(nsecs), mode);
out:
__bpf_spin_unlock_irqrestore(&timer->lock);
return ret;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 464ca3f01fe7..7f5b71847984 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4951,6 +4951,12 @@ union bpf_attr {
* different maps if key/value layout matches across maps.
* Every bpf_timer_set_callback() can have different callback_fn.
*
+ * *flags* can be one of:
+ *
+ * **BPF_F_TIMER_ABS**
+ * Start the timer in absolute expire value instead of the
+ * default relative one.
+ *
* Return
* 0 on success.
* **-EINVAL** if *timer* was not initialized with bpf_timer_init() earlier
@@ -7050,4 +7056,13 @@ struct bpf_core_relo {
enum bpf_core_relo_kind kind;
};
+/*
+ * Flags to control bpf_timer_start() behaviour.
+ * - BPF_F_TIMER_ABS: Timeout passed is absolute time, by default it is
+ * relative to current time.
+ */
+enum {
+ BPF_F_TIMER_ABS = (1ULL << 0),
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
--
2.25.1
Add test for the absolute BPF timer under the existing timer tests. This
will run the timer two times with 1us expiration time, and then re-arm
the timer at ~35s in the future. At the end, it is verified that the
absolute timer expired exactly two times.
Signed-off-by: Tero Kristo <[email protected]>
---
v2: new patch added
.../testing/selftests/bpf/prog_tests/timer.c | 3 ++
tools/testing/selftests/bpf/progs/timer.c | 45 +++++++++++++++++++
2 files changed, 48 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/timer.c b/tools/testing/selftests/bpf/prog_tests/timer.c
index 7eb049214859..290c21dbe65a 100644
--- a/tools/testing/selftests/bpf/prog_tests/timer.c
+++ b/tools/testing/selftests/bpf/prog_tests/timer.c
@@ -29,6 +29,9 @@ static int timer(struct timer *timer_skel)
/* check that timer_cb2() was executed twice */
ASSERT_EQ(timer_skel->bss->bss_data, 10, "bss_data");
+ /* check that timer_cb3() was executed twice */
+ ASSERT_EQ(timer_skel->bss->abs_data, 12, "abs_data");
+
/* check that there were no errors in timer execution */
ASSERT_EQ(timer_skel->bss->err, 0, "err");
diff --git a/tools/testing/selftests/bpf/progs/timer.c b/tools/testing/selftests/bpf/progs/timer.c
index acda5c9cea93..9a16d95213e1 100644
--- a/tools/testing/selftests/bpf/progs/timer.c
+++ b/tools/testing/selftests/bpf/progs/timer.c
@@ -46,7 +46,15 @@ struct {
__type(value, struct elem);
} lru SEC(".maps");
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, int);
+ __type(value, struct elem);
+} abs_timer SEC(".maps");
+
__u64 bss_data;
+__u64 abs_data;
__u64 err;
__u64 ok;
__u64 callback_check = 52;
@@ -284,3 +292,40 @@ int BPF_PROG2(test2, int, a, int, b)
return bpf_timer_test();
}
+
+/* callback for absolute timer */
+static int timer_cb3(void *map, int *key, struct bpf_timer *timer)
+{
+ abs_data += 6;
+
+ if (abs_data < 12) {
+ bpf_timer_start(timer, bpf_ktime_get_boot_ns() + 1000,
+ BPF_F_TIMER_ABS);
+ } else {
+ /* Re-arm timer ~35 seconds in future */
+ bpf_timer_start(timer, bpf_ktime_get_boot_ns() + (1ull << 35),
+ BPF_F_TIMER_ABS);
+ }
+
+ return 0;
+}
+
+SEC("fentry/bpf_fentry_test3")
+int BPF_PROG2(test3, int, a)
+{
+ int key = 0;
+ struct bpf_timer *timer;
+
+ bpf_printk("test3");
+
+ timer = bpf_map_lookup_elem(&abs_timer, &key);
+ if (timer) {
+ if (bpf_timer_init(timer, &abs_timer, CLOCK_BOOTTIME) != 0)
+ err |= 2048;
+ bpf_timer_set_callback(timer, timer_cb3);
+ bpf_timer_start(timer, bpf_ktime_get_boot_ns() + 1000,
+ BPF_F_TIMER_ABS);
+ }
+
+ return 0;
+}
--
2.25.1
Hello:
This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <[email protected]>:
On Thu, 2 Mar 2023 13:46:12 +0200 you wrote:
> Hi,
>
> v2 of this series just adds the selftest support. Patch #1 is modified
> slightly (bpf.h modified under tools/include) so that the new selftest
> compiles properly. I also added suggested-by tag from Artem whom I
> forgot to add in the initial upstream post.
>
> [...]
Here is the summary with links:
- [PATCHv2,1/2] bpf: Add support for absolute value BPF timers
https://git.kernel.org/bpf/bpf-next/c/f71f8530494b
- [PATCHv2,2/2] selftests/bpf: Add absolute timer test
https://git.kernel.org/bpf/bpf-next/c/944459e88b4f
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html