[PATCH bpf-next 1/8] bpf: consolidate shared test timing code

[Lorenz Bauer <lmb@cloudflare.com>]

Share the timing / signal interruption logic between different
implementations of PROG_TEST_RUN. There is a change in behaviour
as well. We check the loop exit condition before checking for
pending signals. This resolves an edge case where a signal
arrives during the last iteration. Instead of aborting with
EINTR we return the successful result to user space.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
---
 net/bpf/test_run.c | 137 +++++++++++++++++++++++++--------------------
 1 file changed, 76 insertions(+), 61 deletions(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 58bcb8c849d5..33bd2f67e259 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -16,14 +16,82 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/bpf_test_run.h>
 
+struct test_timer {
+	enum { NO_PREEMPT, NO_MIGRATE } mode;
+	u32 i;
+	u64 time_start, time_spent;
+};
+
+static inline void t_enter(struct test_timer *t)
+{
+	rcu_read_lock();
+	if (t->mode == NO_PREEMPT)
+		preempt_disable();
+	else
+		migrate_disable();
+
+	t->time_start = ktime_get_ns();
+}
+
+static inline void t_leave(struct test_timer *t)
+{
+	t->time_spent += ktime_get_ns() - t->time_start;
+	t->time_start = 0;
+
+	if (t->mode == NO_PREEMPT)
+		preempt_enable();
+	else
+		migrate_enable();
+	rcu_read_unlock();
+}
+
+static inline bool t_check(struct test_timer *t, u32 repeat, int *err, u32 *duration)
+{
+	if (!t->time_start) {
+		/* Enter protected section before first iteration. */
+		t_enter(t);
+		return true;
+	}
+
+	t->i++;
+	if (t->i >= repeat) {
+		/* Leave the protected section after the last iteration. */
+		t_leave(t);
+		do_div(t->time_spent, t->i);
+		*duration = t->time_spent > U32_MAX ? U32_MAX : (u32)t->time_spent;
+		*err = 0;
+		goto reset;
+	}
+
+	if (signal_pending(current)) {
+		/* During iteration: we've been cancelled, abort. */
+		t_leave(t);
+		*err = -EINTR;
+		goto reset;
+	}
+
+	if (need_resched()) {
+		/* During iteration: we need to reschedule between runs. */
+		t_leave(t);
+		cond_resched();
+		t_enter(t);
+	}
+
+	/* Do another round. */
+	return true;
+
+reset:
+	t->time_spent = t->i = 0;
+	return false;
+}
+
 static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
 			u32 *retval, u32 *time, bool xdp)
 {
 	struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE] = { NULL };
+	struct test_timer t = { NO_MIGRATE };
 	enum bpf_cgroup_storage_type stype;
-	u64 time_start, time_spent = 0;
-	int ret = 0;
-	u32 i;
+	int ret;
 
 	for_each_cgroup_storage_type(stype) {
 		storage[stype] = bpf_cgroup_storage_alloc(prog, stype);
@@ -38,40 +106,14 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
 	if (!repeat)
 		repeat = 1;
 
-	rcu_read_lock();
-	migrate_disable();
-	time_start = ktime_get_ns();
-	for (i = 0; i < repeat; i++) {
+	while (t_check(&t, repeat, &ret, time)) {
 		bpf_cgroup_storage_set(storage);
 
 		if (xdp)
 			*retval = bpf_prog_run_xdp(prog, ctx);
 		else
 			*retval = BPF_PROG_RUN(prog, ctx);
-
-		if (signal_pending(current)) {
-			ret = -EINTR;
-			break;
-		}
-
-		if (need_resched()) {
-			time_spent += ktime_get_ns() - time_start;
-			migrate_enable();
-			rcu_read_unlock();
-
-			cond_resched();
-
-			rcu_read_lock();
-			migrate_disable();
-			time_start = ktime_get_ns();
-		}
 	}
-	time_spent += ktime_get_ns() - time_start;
-	migrate_enable();
-	rcu_read_unlock();
-
-	do_div(time_spent, repeat);
-	*time = time_spent > U32_MAX ? U32_MAX : (u32)time_spent;
 
 	for_each_cgroup_storage_type(stype)
 		bpf_cgroup_storage_free(storage[stype]);
@@ -674,18 +716,17 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
 				     const union bpf_attr *kattr,
 				     union bpf_attr __user *uattr)
 {
+	struct test_timer t = { NO_PREEMPT };
 	u32 size = kattr->test.data_size_in;
 	struct bpf_flow_dissector ctx = {};
 	u32 repeat = kattr->test.repeat;
 	struct bpf_flow_keys *user_ctx;
 	struct bpf_flow_keys flow_keys;
-	u64 time_start, time_spent = 0;
 	const struct ethhdr *eth;
 	unsigned int flags = 0;
 	u32 retval, duration;
 	void *data;
 	int ret;
-	u32 i;
 
 	if (prog->type != BPF_PROG_TYPE_FLOW_DISSECTOR)
 		return -EINVAL;
@@ -721,39 +762,13 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
 	ctx.data = data;
 	ctx.data_end = (__u8 *)data + size;
 
-	rcu_read_lock();
-	preempt_disable();
-	time_start = ktime_get_ns();
-	for (i = 0; i < repeat; i++) {
+	while (t_check(&t, repeat, &ret, &duration)) {
 		retval = bpf_flow_dissect(prog, &ctx, eth->h_proto, ETH_HLEN,
 					  size, flags);
-
-		if (signal_pending(current)) {
-			preempt_enable();
-			rcu_read_unlock();
-
-			ret = -EINTR;
-			goto out;
-		}
-
-		if (need_resched()) {
-			time_spent += ktime_get_ns() - time_start;
-			preempt_enable();
-			rcu_read_unlock();
-
-			cond_resched();
-
-			rcu_read_lock();
-			preempt_disable();
-			time_start = ktime_get_ns();
-		}
 	}
-	time_spent += ktime_get_ns() - time_start;
-	preempt_enable();
-	rcu_read_unlock();
 
-	do_div(time_spent, repeat);
-	duration = time_spent > U32_MAX ? U32_MAX : (u32)time_spent;
+	if (ret < 0)
+		goto out;
 
 	ret = bpf_test_finish(kattr, uattr, &flow_keys, sizeof(flow_keys),
 			      retval, duration);
-- 
2.27.0