1 files changed, 343 insertions, 9 deletions

diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index 6533ea9b044c..96e7d853b9ed 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -11,6 +11,12 @@
 /* for collect_lock_syms().  4096 was rejected by the verifier */
 #define MAX_CPUS  1024
 
+/* for collect_zone_lock().  It should be more than the actual zones. */
+#define MAX_ZONES  10
+
+/* for do_lock_delay().  Arbitrarily set to 1 million. */
+#define MAX_LOOP  (1U << 20)
+
 /* lock contention flags from include/trace/events/lock.h */
 #define LCB_F_SPIN	(1U << 0)
 #define LCB_F_READ	(1U << 1)
@@ -27,6 +33,38 @@ struct {
 	__uint(max_entries, MAX_ENTRIES);
 } stacks SEC(".maps");
 
+/* buffer for owner stacktrace */
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(__u64));
+	__uint(max_entries, 1);
+} stack_buf SEC(".maps");
+
+/* a map for tracing owner stacktrace to owner stack id */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u64)); // owner stacktrace
+	__uint(value_size, sizeof(__s32)); // owner stack id
+	__uint(max_entries, 1);
+} owner_stacks SEC(".maps");
+
+/* a map for tracing lock address to owner data */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u64)); // lock address
+	__uint(value_size, sizeof(struct owner_tracing_data));
+	__uint(max_entries, 1);
+} owner_data SEC(".maps");
+
+/* a map for contention_key (stores owner stack id) to contention data */
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(struct contention_key));
+	__uint(value_size, sizeof(struct contention_data));
+	__uint(max_entries, 1);
+} owner_stat SEC(".maps");
+
 /* maintain timestamp at the beginning of contention */
 struct {
 	__uint(type, BPF_MAP_TYPE_HASH);
@@ -114,6 +152,13 @@ struct {
 	__uint(max_entries, 1);
 } slab_caches SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(__u64));
+	__uint(value_size, sizeof(__u64));
+	__uint(max_entries, 1);
+} lock_delays SEC(".maps");
+
 struct rw_semaphore___old {
 	struct task_struct *owner;
 } __attribute__((preserve_access_index));
@@ -143,6 +188,8 @@ const volatile int needs_callstack;
 const volatile int stack_skip;
 const volatile int lock_owner;
 const volatile int use_cgroup_v2;
+const volatile int max_stack;
+const volatile int lock_delay;
 
 /* determine the key of lock stat */
 const volatile int aggr_mode;
@@ -164,6 +211,9 @@ int data_fail;
 int task_map_full;
 int data_map_full;
 
+struct task_struct *bpf_task_from_pid(s32 pid) __ksym __weak;
+void bpf_task_release(struct task_struct *p) __ksym __weak;
+
 static inline __u64 get_current_cgroup_id(void)
 {
 	struct task_struct *task;
@@ -348,6 +398,35 @@ static inline __u32 check_lock_type(__u64 lock, __u32 flags)
 	return 0;
 }
 
+static inline long delay_callback(__u64 idx, void *arg)
+{
+	__u64 target = *(__u64 *)arg;
+
+	if (target <= bpf_ktime_get_ns())
+		return 1;
+
+	/* just to kill time */
+	(void)bpf_get_prandom_u32();
+
+	return 0;
+}
+
+static inline void do_lock_delay(__u64 duration)
+{
+	__u64 target = bpf_ktime_get_ns() + duration;
+
+	bpf_loop(MAX_LOOP, delay_callback, &target, /*flags=*/0);
+}
+
+static inline void check_lock_delay(__u64 lock)
+{
+	__u64 *delay;
+
+	delay = bpf_map_lookup_elem(&lock_delays, &lock);
+	if (delay)
+		do_lock_delay(*delay);
+}
+
 static inline struct tstamp_data *get_tstamp_elem(__u32 flags)
 {
 	__u32 pid;
@@ -387,6 +466,61 @@ static inline struct tstamp_data *get_tstamp_elem(__u32 flags)
 	return pelem;
 }
 
+static inline s32 get_owner_stack_id(u64 *stacktrace)
+{
+	s32 *id, new_id;
+	static s64 id_gen = 1;
+
+	id = bpf_map_lookup_elem(&owner_stacks, stacktrace);
+	if (id)
+		return *id;
+
+	new_id = (s32)__sync_fetch_and_add(&id_gen, 1);
+
+	bpf_map_update_elem(&owner_stacks, stacktrace, &new_id, BPF_NOEXIST);
+
+	id = bpf_map_lookup_elem(&owner_stacks, stacktrace);
+	if (id)
+		return *id;
+
+	return -1;
+}
+
+static inline void update_contention_data(struct contention_data *data, u64 duration, u32 count)
+{
+	__sync_fetch_and_add(&data->total_time, duration);
+	__sync_fetch_and_add(&data->count, count);
+
+	/* FIXME: need atomic operations */
+	if (data->max_time < duration)
+		data->max_time = duration;
+	if (data->min_time > duration)
+		data->min_time = duration;
+}
+
+static inline void update_owner_stat(u32 id, u64 duration, u32 flags)
+{
+	struct contention_key key = {
+		.stack_id = id,
+		.pid = 0,
+		.lock_addr_or_cgroup = 0,
+	};
+	struct contention_data *data = bpf_map_lookup_elem(&owner_stat, &key);
+
+	if (!data) {
+		struct contention_data first = {
+			.total_time = duration,
+			.max_time = duration,
+			.min_time = duration,
+			.count = 1,
+			.flags = flags,
+		};
+		bpf_map_update_elem(&owner_stat, &key, &first, BPF_NOEXIST);
+	} else {
+		update_contention_data(data, duration, 1);
+	}
+}
+
 SEC("tp_btf/contention_begin")
 int contention_begin(u64 *ctx)
 {
@@ -404,6 +538,72 @@ int contention_begin(u64 *ctx)
 	pelem->flags = (__u32)ctx[1];
 
 	if (needs_callstack) {
+		u32 i = 0;
+		u32 id = 0;
+		int owner_pid;
+		u64 *buf;
+		struct task_struct *task;
+		struct owner_tracing_data *otdata;
+
+		if (!lock_owner)
+			goto skip_owner;
+
+		task = get_lock_owner(pelem->lock, pelem->flags);
+		if (!task)
+			goto skip_owner;
+
+		owner_pid = BPF_CORE_READ(task, pid);
+
+		buf = bpf_map_lookup_elem(&stack_buf, &i);
+		if (!buf)
+			goto skip_owner;
+		for (i = 0; i < max_stack; i++)
+			buf[i] = 0x0;
+
+		if (!bpf_task_from_pid)
+			goto skip_owner;
+
+		task = bpf_task_from_pid(owner_pid);
+		if (!task)
+			goto skip_owner;
+
+		bpf_get_task_stack(task, buf, max_stack * sizeof(unsigned long), 0);
+		bpf_task_release(task);
+
+		otdata = bpf_map_lookup_elem(&owner_data, &pelem->lock);
+		id = get_owner_stack_id(buf);
+
+		/*
+		 * Contention just happens, or corner case `lock` is owned by process not
+		 * `owner_pid`. For the corner case we treat it as unexpected internal error and
+		 * just ignore the precvious tracing record.
+		 */
+		if (!otdata || otdata->pid != owner_pid) {
+			struct owner_tracing_data first = {
+				.pid = owner_pid,
+				.timestamp = pelem->timestamp,
+				.count = 1,
+				.stack_id = id,
+			};
+			bpf_map_update_elem(&owner_data, &pelem->lock, &first, BPF_ANY);
+		}
+		/* Contention is ongoing and new waiter joins */
+		else {
+			__sync_fetch_and_add(&otdata->count, 1);
+
+			/*
+			 * The owner is the same, but stacktrace might be changed. In this case we
+			 * store/update `owner_stat` based on current owner stack id.
+			 */
+			if (id != otdata->stack_id) {
+				update_owner_stat(id, pelem->timestamp - otdata->timestamp,
+						  pelem->flags);
+
+				otdata->timestamp = pelem->timestamp;
+				otdata->stack_id = id;
+			}
+		}
+skip_owner:
 		pelem->stack_id = bpf_get_stackid(ctx, &stacks,
 						  BPF_F_FAST_STACK_CMP | stack_skip);
 		if (pelem->stack_id < 0)
@@ -440,6 +640,7 @@ int contention_end(u64 *ctx)
 	struct tstamp_data *pelem;
 	struct contention_key key = {};
 	struct contention_data *data;
+	__u64 timestamp;
 	__u64 duration;
 	bool need_delete = false;
 
@@ -467,12 +668,88 @@ int contention_end(u64 *ctx)
 		need_delete = true;
 	}
 
-	duration = bpf_ktime_get_ns() - pelem->timestamp;
+	timestamp = bpf_ktime_get_ns();
+	duration = timestamp - pelem->timestamp;
 	if ((__s64)duration < 0) {
 		__sync_fetch_and_add(&time_fail, 1);
 		goto out;
 	}
 
+	if (needs_callstack && lock_owner) {
+		struct owner_tracing_data *otdata = bpf_map_lookup_elem(&owner_data, &pelem->lock);
+
+		if (!otdata)
+			goto skip_owner;
+
+		/* Update `owner_stat` */
+		update_owner_stat(otdata->stack_id, timestamp - otdata->timestamp, pelem->flags);
+
+		/* No contention is occurring, delete `lock` entry in `owner_data` */
+		if (otdata->count <= 1)
+			bpf_map_delete_elem(&owner_data, &pelem->lock);
+		/*
+		 * Contention is still ongoing, with a new owner (current task). `owner_data`
+		 * should be updated accordingly.
+		 */
+		else {
+			u32 i = 0;
+			s32 ret = (s32)ctx[1];
+			u64 *buf;
+
+			otdata->timestamp = timestamp;
+			__sync_fetch_and_add(&otdata->count, -1);
+
+			buf = bpf_map_lookup_elem(&stack_buf, &i);
+			if (!buf)
+				goto skip_owner;
+			for (i = 0; i < (u32)max_stack; i++)
+				buf[i] = 0x0;
+
+			/*
+			 * `ret` has the return code of the lock function.
+			 * If `ret` is negative, the current task terminates lock waiting without
+			 * acquiring it. Owner is not changed, but we still need to update the owner
+			 * stack.
+			 */
+			if (ret < 0) {
+				s32 id = 0;
+				struct task_struct *task;
+
+				if (!bpf_task_from_pid)
+					goto skip_owner;
+
+				task = bpf_task_from_pid(otdata->pid);
+				if (!task)
+					goto skip_owner;
+
+				bpf_get_task_stack(task, buf,
+						   max_stack * sizeof(unsigned long), 0);
+				bpf_task_release(task);
+
+				id = get_owner_stack_id(buf);
+
+				/*
+				 * If owner stack is changed, update owner stack id for this lock.
+				 */
+				if (id != otdata->stack_id)
+					otdata->stack_id = id;
+			}
+			/*
+			 * Otherwise, update tracing data with the current task, which is the new
+			 * owner.
+			 */
+			else {
+				otdata->pid = pid;
+				/*
+				 * We don't want to retrieve callstack here, since it is where the
+				 * current task acquires the lock and provides no additional
+				 * information. We simply assign -1 to invalidate it.
+				 */
+				otdata->stack_id = -1;
+			}
+		}
+	}
+skip_owner:
 	switch (aggr_mode) {
 	case LOCK_AGGR_CALLER:
 		key.stack_id = pelem->stack_id;
@@ -556,16 +833,12 @@ int contention_end(u64 *ctx)
 	}
 
 found:
-	__sync_fetch_and_add(&data->total_time, duration);
-	__sync_fetch_and_add(&data->count, 1);
-
-	/* FIXME: need atomic operations */
-	if (data->max_time < duration)
-		data->max_time = duration;
-	if (data->min_time > duration)
-		data->min_time = duration;
+	update_contention_data(data, duration, 1);
 
 out:
+	if (lock_delay)
+		check_lock_delay(pelem->lock);
+
 	pelem->lock = 0;
 	if (need_delete)
 		bpf_map_delete_elem(&tstamp, &pid);
@@ -574,6 +847,11 @@ out:
 
 extern struct rq runqueues __ksym;
 
+const volatile __u64 contig_page_data_addr;
+const volatile __u64 node_data_addr;
+const volatile int nr_nodes;
+const volatile int sizeof_zone;
+
 struct rq___old {
 	raw_spinlock_t lock;
 } __attribute__((preserve_access_index));
@@ -582,6 +860,59 @@ struct rq___new {
 	raw_spinlock_t __lock;
 } __attribute__((preserve_access_index));
 
+static void collect_zone_lock(void)
+{
+	__u64 nr_zones, zone_off;
+	__u64 lock_addr, lock_off;
+	__u32 lock_flag = LOCK_CLASS_ZONE_LOCK;
+
+	zone_off = offsetof(struct pglist_data, node_zones);
+	lock_off = offsetof(struct zone, lock);
+
+	if (contig_page_data_addr) {
+		struct pglist_data *contig_page_data;
+
+		contig_page_data = (void *)(long)contig_page_data_addr;
+		nr_zones = BPF_CORE_READ(contig_page_data, nr_zones);
+
+		for (int i = 0; i < MAX_ZONES; i++) {
+			__u64 zone_addr;
+
+			if (i >= nr_zones)
+				break;
+
+			zone_addr = contig_page_data_addr + (sizeof_zone * i) + zone_off;
+			lock_addr = zone_addr + lock_off;
+
+			bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);
+		}
+	} else if (nr_nodes > 0) {
+		struct pglist_data **node_data = (void *)(long)node_data_addr;
+
+		for (int i = 0; i < nr_nodes; i++) {
+			struct pglist_data *pgdat = NULL;
+			int err;
+
+			err = bpf_core_read(&pgdat, sizeof(pgdat), &node_data[i]);
+			if (err < 0 || pgdat == NULL)
+				break;
+
+			nr_zones = BPF_CORE_READ(pgdat, nr_zones);
+			for (int k = 0; k < MAX_ZONES; k++) {
+				__u64 zone_addr;
+
+				if (k >= nr_zones)
+					break;
+
+				zone_addr = (__u64)(void *)pgdat + (sizeof_zone * k) + zone_off;
+				lock_addr = zone_addr + lock_off;
+
+				bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);
+			}
+		}
+	}
+}
+
 SEC("raw_tp/bpf_test_finish")
 int BPF_PROG(collect_lock_syms)
 {
@@ -603,6 +934,9 @@ int BPF_PROG(collect_lock_syms)
 		lock_flag = LOCK_CLASS_RQLOCK;
 		bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);
 	}
+
+	collect_zone_lock();
+
 	return 0;
 }