tools/perf/util/bpf_skel/lock_contention.bpf.c

   1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
   2 // Copyright (c) 2022 Google
   3 #include "vmlinux.h"
   4 #include <bpf/bpf_helpers.h>
   5 #include <bpf/bpf_tracing.h>
   6 #include <bpf/bpf_core_read.h>
   7
   8 #include "lock_data.h"
   9
  10 /* default buffer size */
  11 #define MAX_ENTRIES  10240
  12
  13 /* for collect_lock_syms().  4096 was rejected by the verifier */
  14 #define MAX_CPUS  1024
  15
  16 /* lock contention flags from include/trace/events/lock.h */
  17 #define LCB_F_SPIN      (1U << 0)
  18 #define LCB_F_READ      (1U << 1)
  19 #define LCB_F_WRITE     (1U << 2)
  20 #define LCB_F_RT        (1U << 3)
  21 #define LCB_F_PERCPU    (1U << 4)
  22 #define LCB_F_MUTEX     (1U << 5)
  23
  24 struct tstamp_data {
  25         __u64 timestamp;
  26         __u64 lock;
  27         __u32 flags;
  28         __s32 stack_id;
  29 };
  30
  31 /* callstack storage  */
  32 struct {
  33         __uint(type, BPF_MAP_TYPE_STACK_TRACE);
  34         __uint(key_size, sizeof(__u32));
  35         __uint(value_size, sizeof(__u64));
  36         __uint(max_entries, MAX_ENTRIES);
  37 } stacks SEC(".maps");
  38
  39 /* maintain timestamp at the beginning of contention */
  40 struct {
  41         __uint(type, BPF_MAP_TYPE_HASH);
  42         __type(key, int);
  43         __type(value, struct tstamp_data);
  44         __uint(max_entries, MAX_ENTRIES);
  45 } tstamp SEC(".maps");
  46
  47 /* actual lock contention statistics */
  48 struct {
  49         __uint(type, BPF_MAP_TYPE_HASH);
  50         __uint(key_size, sizeof(struct contention_key));
  51         __uint(value_size, sizeof(struct contention_data));
  52         __uint(max_entries, MAX_ENTRIES);
  53 } lock_stat SEC(".maps");
  54
  55 struct {
  56         __uint(type, BPF_MAP_TYPE_HASH);
  57         __uint(key_size, sizeof(__u32));
  58         __uint(value_size, sizeof(struct contention_task_data));
  59         __uint(max_entries, MAX_ENTRIES);
  60 } task_data SEC(".maps");
  61
  62 struct {
  63         __uint(type, BPF_MAP_TYPE_HASH);
  64         __uint(key_size, sizeof(__u64));
  65         __uint(value_size, sizeof(__u32));
  66         __uint(max_entries, 16384);
  67 } lock_syms SEC(".maps");
  68
  69 struct {
  70         __uint(type, BPF_MAP_TYPE_HASH);
  71         __uint(key_size, sizeof(__u32));
  72         __uint(value_size, sizeof(__u8));
  73         __uint(max_entries, 1);
  74 } cpu_filter SEC(".maps");
  75
  76 struct {
  77         __uint(type, BPF_MAP_TYPE_HASH);
  78         __uint(key_size, sizeof(__u32));
  79         __uint(value_size, sizeof(__u8));
  80         __uint(max_entries, 1);
  81 } task_filter SEC(".maps");
  82
  83 struct {
  84         __uint(type, BPF_MAP_TYPE_HASH);
  85         __uint(key_size, sizeof(__u32));
  86         __uint(value_size, sizeof(__u8));
  87         __uint(max_entries, 1);
  88 } type_filter SEC(".maps");
  89
  90 struct {
  91         __uint(type, BPF_MAP_TYPE_HASH);
  92         __uint(key_size, sizeof(__u64));
  93         __uint(value_size, sizeof(__u8));
  94         __uint(max_entries, 1);
  95 } addr_filter SEC(".maps");
  96
  97 struct rw_semaphore___old {
  98         struct task_struct *owner;
  99 } __attribute__((preserve_access_index));
 100
 101 struct rw_semaphore___new {
 102         atomic_long_t owner;
 103 } __attribute__((preserve_access_index));
 104
 105 struct mm_struct___old {
 106         struct rw_semaphore mmap_sem;
 107 } __attribute__((preserve_access_index));
 108
 109 struct mm_struct___new {
 110         struct rw_semaphore mmap_lock;
 111 } __attribute__((preserve_access_index));
 112
 113 /* control flags */
 114 int enabled;
 115 int has_cpu;
 116 int has_task;
 117 int has_type;
 118 int has_addr;
 119 int needs_callstack;
 120 int stack_skip;
 121 int lock_owner;
 122
 123 /* determine the key of lock stat */
 124 int aggr_mode;
 125
 126 /* error stat */
 127 int lost;
 128
 129 static inline int can_record(u64 *ctx)
 130 {
 131         if (has_cpu) {
 132                 __u32 cpu = bpf_get_smp_processor_id();
 133                 __u8 *ok;
 134
 135                 ok = bpf_map_lookup_elem(&cpu_filter, &cpu);
 136                 if (!ok)
 137                         return 0;
 138         }
 139
 140         if (has_task) {
 141                 __u8 *ok;
 142                 __u32 pid = bpf_get_current_pid_tgid();
 143
 144                 ok = bpf_map_lookup_elem(&task_filter, &pid);
 145                 if (!ok)
 146                         return 0;
 147         }
 148
 149         if (has_type) {
 150                 __u8 *ok;
 151                 __u32 flags = (__u32)ctx[1];
 152
 153                 ok = bpf_map_lookup_elem(&type_filter, &flags);
 154                 if (!ok)
 155                         return 0;
 156         }
 157
 158         if (has_addr) {
 159                 __u8 *ok;
 160                 __u64 addr = ctx[0];
 161
 162                 ok = bpf_map_lookup_elem(&addr_filter, &addr);
 163                 if (!ok)
 164                         return 0;
 165         }
 166
 167         return 1;
 168 }
 169
 170 static inline int update_task_data(struct task_struct *task)
 171 {
 172         struct contention_task_data *p;
 173         int pid, err;
 174
 175         err = bpf_core_read(&pid, sizeof(pid), &task->pid);
 176         if (err)
 177                 return -1;
 178
 179         p = bpf_map_lookup_elem(&task_data, &pid);
 180         if (p == NULL) {
 181                 struct contention_task_data data = {};
 182
 183                 BPF_CORE_READ_STR_INTO(&data.comm, task, comm);
 184                 bpf_map_update_elem(&task_data, &pid, &data, BPF_NOEXIST);
 185         }
 186
 187         return 0;
 188 }
 189
 190 #ifndef __has_builtin
 191 # define __has_builtin(x) 0
 192 #endif
 193
 194 static inline struct task_struct *get_lock_owner(__u64 lock, __u32 flags)
 195 {
 196         struct task_struct *task;
 197         __u64 owner = 0;
 198
 199         if (flags & LCB_F_MUTEX) {
 200                 struct mutex *mutex = (void *)lock;
 201                 owner = BPF_CORE_READ(mutex, owner.counter);
 202         } else if (flags == LCB_F_READ || flags == LCB_F_WRITE) {
 203         /*
 204          * Support for the BPF_TYPE_MATCHES argument to the
 205          * __builtin_preserve_type_info builtin was added at some point during
 206          * development of clang 15 and it's what is needed for
 207          * bpf_core_type_matches.
 208          */
 209 #if __has_builtin(__builtin_preserve_type_info) && __clang_major__ >= 15
 210                 if (bpf_core_type_matches(struct rw_semaphore___old)) {
 211                         struct rw_semaphore___old *rwsem = (void *)lock;
 212                         owner = (unsigned long)BPF_CORE_READ(rwsem, owner);
 213                 } else if (bpf_core_type_matches(struct rw_semaphore___new)) {
 214                         struct rw_semaphore___new *rwsem = (void *)lock;
 215                         owner = BPF_CORE_READ(rwsem, owner.counter);
 216                 }
 217 #else
 218                 /* assume new struct */
 219                 struct rw_semaphore *rwsem = (void *)lock;
 220                 owner = BPF_CORE_READ(rwsem, owner.counter);
 221 #endif
 222         }
 223
 224         if (!owner)
 225                 return NULL;
 226
 227         task = (void *)(owner & ~7UL);
 228         return task;
 229 }
 230
 231 static inline __u32 check_lock_type(__u64 lock, __u32 flags)
 232 {
 233         struct task_struct *curr;
 234         struct mm_struct___old *mm_old;
 235         struct mm_struct___new *mm_new;
 236
 237         switch (flags) {
 238         case LCB_F_READ:  /* rwsem */
 239         case LCB_F_WRITE:
 240                 curr = bpf_get_current_task_btf();
 241                 if (curr->mm == NULL)
 242                         break;
 243                 mm_new = (void *)curr->mm;
 244                 if (bpf_core_field_exists(mm_new->mmap_lock)) {
 245                         if (&mm_new->mmap_lock == (void *)lock)
 246                                 return LCD_F_MMAP_LOCK;
 247                         break;
 248                 }
 249                 mm_old = (void *)curr->mm;
 250                 if (bpf_core_field_exists(mm_old->mmap_sem)) {
 251                         if (&mm_old->mmap_sem == (void *)lock)
 252                                 return LCD_F_MMAP_LOCK;
 253                 }
 254                 break;
 255         case LCB_F_SPIN:  /* spinlock */
 256                 curr = bpf_get_current_task_btf();
 257                 if (&curr->sighand->siglock == (void *)lock)
 258                         return LCD_F_SIGHAND_LOCK;
 259                 break;
 260         default:
 261                 break;
 262         }
 263         return 0;
 264 }
 265
 266 SEC("tp_btf/contention_begin")
 267 int contention_begin(u64 *ctx)
 268 {
 269         __u32 pid;
 270         struct tstamp_data *pelem;
 271
 272         if (!enabled || !can_record(ctx))
 273                 return 0;
 274
 275         pid = bpf_get_current_pid_tgid();
 276         pelem = bpf_map_lookup_elem(&tstamp, &pid);
 277         if (pelem && pelem->lock)
 278                 return 0;
 279
 280         if (pelem == NULL) {
 281                 struct tstamp_data zero = {};
 282
 283                 bpf_map_update_elem(&tstamp, &pid, &zero, BPF_ANY);
 284                 pelem = bpf_map_lookup_elem(&tstamp, &pid);
 285                 if (pelem == NULL) {
 286                         lost++;
 287                         return 0;
 288                 }
 289         }
 290
 291         pelem->timestamp = bpf_ktime_get_ns();
 292         pelem->lock = (__u64)ctx[0];
 293         pelem->flags = (__u32)ctx[1];
 294
 295         if (needs_callstack) {
 296                 pelem->stack_id = bpf_get_stackid(ctx, &stacks,
 297                                                   BPF_F_FAST_STACK_CMP | stack_skip);
 298                 if (pelem->stack_id < 0)
 299                         lost++;
 300         } else if (aggr_mode == LOCK_AGGR_TASK) {
 301                 struct task_struct *task;
 302
 303                 if (lock_owner) {
 304                         task = get_lock_owner(pelem->lock, pelem->flags);
 305
 306                         /* The flags is not used anymore.  Pass the owner pid. */
 307                         if (task)
 308                                 pelem->flags = BPF_CORE_READ(task, pid);
 309                         else
 310                                 pelem->flags = -1U;
 311
 312                 } else {
 313                         task = bpf_get_current_task_btf();
 314                 }
 315
 316                 if (task) {
 317                         if (update_task_data(task) < 0 && lock_owner)
 318                                 pelem->flags = -1U;
 319                 }
 320         }
 321
 322         return 0;
 323 }
 324
 325 SEC("tp_btf/contention_end")
 326 int contention_end(u64 *ctx)
 327 {
 328         __u32 pid;
 329         struct tstamp_data *pelem;
 330         struct contention_key key = {};
 331         struct contention_data *data;
 332         __u64 duration;
 333
 334         if (!enabled)
 335                 return 0;
 336
 337         pid = bpf_get_current_pid_tgid();
 338         pelem = bpf_map_lookup_elem(&tstamp, &pid);
 339         if (!pelem || pelem->lock != ctx[0])
 340                 return 0;
 341
 342         duration = bpf_ktime_get_ns() - pelem->timestamp;
 343
 344         switch (aggr_mode) {
 345         case LOCK_AGGR_CALLER:
 346                 key.stack_id = pelem->stack_id;
 347                 break;
 348         case LOCK_AGGR_TASK:
 349                 if (lock_owner)
 350                         key.pid = pelem->flags;
 351                 else
 352                         key.pid = pid;
 353                 if (needs_callstack)
 354                         key.stack_id = pelem->stack_id;
 355                 break;
 356         case LOCK_AGGR_ADDR:
 357                 key.lock_addr = pelem->lock;
 358                 if (needs_callstack)
 359                         key.stack_id = pelem->stack_id;
 360                 break;
 361         default:
 362                 /* should not happen */
 363                 return 0;
 364         }
 365
 366         data = bpf_map_lookup_elem(&lock_stat, &key);
 367         if (!data) {
 368                 struct contention_data first = {
 369                         .total_time = duration,
 370                         .max_time = duration,
 371                         .min_time = duration,
 372                         .count = 1,
 373                         .flags = pelem->flags,
 374                 };
 375
 376                 if (aggr_mode == LOCK_AGGR_ADDR)
 377                         first.flags |= check_lock_type(pelem->lock, pelem->flags);
 378
 379                 bpf_map_update_elem(&lock_stat, &key, &first, BPF_NOEXIST);
 380                 bpf_map_delete_elem(&tstamp, &pid);
 381                 return 0;
 382         }
 383
 384         __sync_fetch_and_add(&data->total_time, duration);
 385         __sync_fetch_and_add(&data->count, 1);
 386
 387         /* FIXME: need atomic operations */
 388         if (data->max_time < duration)
 389                 data->max_time = duration;
 390         if (data->min_time > duration)
 391                 data->min_time = duration;
 392
 393         bpf_map_delete_elem(&tstamp, &pid);
 394         return 0;
 395 }
 396
 397 extern struct rq runqueues __ksym;
 398
 399 SEC("raw_tp/bpf_test_finish")
 400 int BPF_PROG(collect_lock_syms)
 401 {
 402         __u64 lock_addr;
 403         __u32 lock_flag;
 404
 405         for (int i = 0; i < MAX_CPUS; i++) {
 406                 struct rq *rq = bpf_per_cpu_ptr(&runqueues, i);
 407
 408                 if (rq == NULL)
 409                         break;
 410
 411                 lock_addr = (__u64)&rq->__lock;
 412                 lock_flag = LOCK_CLASS_RQLOCK;
 413                 bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);
 414         }
 415         return 0;
 416 }
 417
 418 char LICENSE[] SEC("license") = "Dual BSD/GPL";