1 files changed, 354 insertions, 39 deletions

diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index d931a898c434..69be7a4234e0 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -27,6 +27,38 @@ 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);
@@ -100,6 +132,20 @@ struct {
 	__uint(max_entries, 1);
 } cgroup_filter SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(long));
+	__uint(value_size, sizeof(__u8));
+	__uint(max_entries, 1);
+} slab_filter SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(key_size, sizeof(long));
+	__uint(value_size, sizeof(struct slab_cache_data));
+	__uint(max_entries, 1);
+} slab_caches SEC(".maps");
+
 struct rw_semaphore___old {
 	struct task_struct *owner;
 } __attribute__((preserve_access_index));
@@ -116,25 +162,32 @@ struct mm_struct___new {
 	struct rw_semaphore mmap_lock;
 } __attribute__((preserve_access_index));
 
+extern struct kmem_cache *bpf_get_kmem_cache(u64 addr) __ksym __weak;
+
 /* control flags */
-int enabled;
-int has_cpu;
-int has_task;
-int has_type;
-int has_addr;
-int has_cgroup;
-int needs_callstack;
-int stack_skip;
-int lock_owner;
-
-int use_cgroup_v2;
-int perf_subsys_id = -1;
+const volatile int has_cpu;
+const volatile int has_task;
+const volatile int has_type;
+const volatile int has_addr;
+const volatile int has_cgroup;
+const volatile int has_slab;
+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;
 
 /* determine the key of lock stat */
-int aggr_mode;
+const volatile int aggr_mode;
+
+int enabled;
+
+int perf_subsys_id = -1;
 
 __u64 end_ts;
 
+__u32 slab_cache_id;
+
 /* error stat */
 int task_fail;
 int stack_fail;
@@ -144,6 +197,9 @@ 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;
@@ -201,7 +257,7 @@ static inline int can_record(u64 *ctx)
 		__u64 addr = ctx[0];
 
 		ok = bpf_map_lookup_elem(&addr_filter, &addr);
-		if (!ok)
+		if (!ok && !has_slab)
 			return 0;
 	}
 
@@ -214,6 +270,17 @@ static inline int can_record(u64 *ctx)
 			return 0;
 	}
 
+	if (has_slab && bpf_get_kmem_cache) {
+		__u8 *ok;
+		__u64 addr = ctx[0];
+		long kmem_cache_addr;
+
+		kmem_cache_addr = (long)bpf_get_kmem_cache(addr);
+		ok = bpf_map_lookup_elem(&slab_filter, &kmem_cache_addr);
+		if (!ok)
+			return 0;
+	}
+
 	return 1;
 }
 
@@ -323,8 +390,7 @@ static inline struct tstamp_data *get_tstamp_elem(__u32 flags)
 	struct tstamp_data *pelem;
 
 	/* Use per-cpu array map for spinlock and rwlock */
-	if (flags == (LCB_F_SPIN | LCB_F_READ) || flags == LCB_F_SPIN ||
-	    flags == (LCB_F_SPIN | LCB_F_WRITE)) {
+	if ((flags & (LCB_F_SPIN | LCB_F_MUTEX)) == LCB_F_SPIN) {
 		__u32 idx = 0;
 
 		pelem = bpf_map_lookup_elem(&tstamp_cpu, &idx);
@@ -357,6 +423,61 @@ 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)
 {
@@ -374,6 +495,72 @@ 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)
@@ -410,6 +597,7 @@ 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;
 
@@ -437,15 +625,88 @@ 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) {
-		pelem->lock = 0;
-		if (need_delete)
-			bpf_map_delete_elem(&tstamp, &pid);
 		__sync_fetch_and_add(&time_fail, 1);
-		return 0;
+		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;
@@ -477,11 +738,8 @@ int contention_end(u64 *ctx)
 	data = bpf_map_lookup_elem(&lock_stat, &key);
 	if (!data) {
 		if (data_map_full) {
-			pelem->lock = 0;
-			if (need_delete)
-				bpf_map_delete_elem(&tstamp, &pid);
 			__sync_fetch_and_add(&data_fail, 1);
-			return 0;
+			goto out;
 		}
 
 		struct contention_data first = {
@@ -493,30 +751,48 @@ int contention_end(u64 *ctx)
 		};
 		int err;
 
-		if (aggr_mode == LOCK_AGGR_ADDR)
-			first.flags |= check_lock_type(pelem->lock, pelem->flags);
+		if (aggr_mode == LOCK_AGGR_ADDR) {
+			first.flags |= check_lock_type(pelem->lock,
+						       pelem->flags & LCB_F_TYPE_MASK);
+
+			/* Check if it's from a slab object */
+			if (bpf_get_kmem_cache) {
+				struct kmem_cache *s;
+				struct slab_cache_data *d;
+
+				s = bpf_get_kmem_cache(pelem->lock);
+				if (s != NULL) {
+					/*
+					 * Save the ID of the slab cache in the flags
+					 * (instead of full address) to reduce the
+					 * space in the contention_data.
+					 */
+					d = bpf_map_lookup_elem(&slab_caches, &s);
+					if (d != NULL)
+						first.flags |= d->id;
+				}
+			}
+		}
 
 		err = bpf_map_update_elem(&lock_stat, &key, &first, BPF_NOEXIST);
 		if (err < 0) {
+			if (err == -EEXIST) {
+				/* it lost the race, try to get it again */
+				data = bpf_map_lookup_elem(&lock_stat, &key);
+				if (data != NULL)
+					goto found;
+			}
 			if (err == -E2BIG)
 				data_map_full = 1;
 			__sync_fetch_and_add(&data_fail, 1);
 		}
-		pelem->lock = 0;
-		if (need_delete)
-			bpf_map_delete_elem(&tstamp, &pid);
-		return 0;
+		goto out;
 	}
 
-	__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;
+found:
+	update_contention_data(data, duration, 1);
 
+out:
 	pelem->lock = 0;
 	if (need_delete)
 		bpf_map_delete_elem(&tstamp, &pid);
@@ -564,4 +840,43 @@ int BPF_PROG(end_timestamp)
 	return 0;
 }
 
+/*
+ * bpf_iter__kmem_cache added recently so old kernels don't have it in the
+ * vmlinux.h.  But we cannot add it here since it will cause a compiler error
+ * due to redefinition of the struct on later kernels.
+ *
+ * So it uses a CO-RE trick to access the member only if it has the type.
+ * This will support both old and new kernels without compiler errors.
+ */
+struct bpf_iter__kmem_cache___new {
+	struct kmem_cache *s;
+} __attribute__((preserve_access_index));
+
+SEC("iter/kmem_cache")
+int slab_cache_iter(void *ctx)
+{
+	struct kmem_cache *s = NULL;
+	struct slab_cache_data d;
+	const char *nameptr;
+
+	if (bpf_core_type_exists(struct bpf_iter__kmem_cache)) {
+		struct bpf_iter__kmem_cache___new *iter = ctx;
+
+		s = iter->s;
+	}
+
+	if (s == NULL)
+		return 0;
+
+	nameptr = s->name;
+	bpf_probe_read_kernel_str(d.name, sizeof(d.name), nameptr);
+
+	d.id = ++slab_cache_id << LCB_F_SLAB_ID_SHIFT;
+	if (d.id >= LCB_F_SLAB_ID_END)
+		return 0;
+
+	bpf_map_update_elem(&slab_caches, &s, &d, BPF_NOEXIST);
+	return 0;
+}
+
 char LICENSE[] SEC("license") = "Dual BSD/GPL";