drivers/oprofile/cpu_buffer.c

   1 /**
   2  * @file cpu_buffer.c
   3  *
   4  * @remark Copyright 2002-2009 OProfile authors
   5  * @remark Read the file COPYING
   6  *
   7  * @author John Levon <levon@movementarian.org>
   8  * @author Barry Kasindorf <barry.kasindorf@amd.com>
   9  * @author Robert Richter <robert.richter@amd.com>
  10  *
  11  * Each CPU has a local buffer that stores PC value/event
  12  * pairs. We also log context switches when we notice them.
  13  * Eventually each CPU's buffer is processed into the global
  14  * event buffer by sync_buffer().
  15  *
  16  * We use a local buffer for two reasons: an NMI or similar
  17  * interrupt cannot synchronise, and high sampling rates
  18  * would lead to catastrophic global synchronisation if
  19  * a global buffer was used.
  20  */
  21
  22 #include <linux/sched.h>
  23 #include <linux/oprofile.h>
  24 #include <linux/vmalloc.h>
  25 #include <linux/errno.h>
  26
  27 #include "event_buffer.h"
  28 #include "cpu_buffer.h"
  29 #include "buffer_sync.h"
  30 #include "oprof.h"
  31
  32 #define OP_BUFFER_FLAGS 0
  33
  34 /*
  35  * Read and write access is using spin locking. Thus, writing to the
  36  * buffer by NMI handler (x86) could occur also during critical
  37  * sections when reading the buffer. To avoid this, there are 2
  38  * buffers for independent read and write access. Read access is in
  39  * process context only, write access only in the NMI handler. If the
  40  * read buffer runs empty, both buffers are swapped atomically. There
  41  * is potentially a small window during swapping where the buffers are
  42  * disabled and samples could be lost.
  43  *
  44  * Using 2 buffers is a little bit overhead, but the solution is clear
  45  * and does not require changes in the ring buffer implementation. It
  46  * can be changed to a single buffer solution when the ring buffer
  47  * access is implemented as non-locking atomic code.
  48  */
  49 static struct ring_buffer *op_ring_buffer_read;
  50 static struct ring_buffer *op_ring_buffer_write;
  51 DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
  52
  53 static void wq_sync_buffer(struct work_struct *work);
  54
  55 #define DEFAULT_TIMER_EXPIRE (HZ / 10)
  56 static int work_enabled;
  57
  58 unsigned long oprofile_get_cpu_buffer_size(void)
  59 {
  60         return oprofile_cpu_buffer_size;
  61 }
  62
  63 void oprofile_cpu_buffer_inc_smpl_lost(void)
  64 {
  65         struct oprofile_cpu_buffer *cpu_buf
  66                 = &__get_cpu_var(cpu_buffer);
  67
  68         cpu_buf->sample_lost_overflow++;
  69 }
  70
  71 void free_cpu_buffers(void)
  72 {
  73         if (op_ring_buffer_read)
  74                 ring_buffer_free(op_ring_buffer_read);
  75         op_ring_buffer_read = NULL;
  76         if (op_ring_buffer_write)
  77                 ring_buffer_free(op_ring_buffer_write);
  78         op_ring_buffer_write = NULL;
  79 }
  80
  81 int alloc_cpu_buffers(void)
  82 {
  83         int i;
  84
  85         unsigned long buffer_size = oprofile_cpu_buffer_size;
  86
  87         op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
  88         if (!op_ring_buffer_read)
  89                 goto fail;
  90         op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
  91         if (!op_ring_buffer_write)
  92                 goto fail;
  93
  94         for_each_possible_cpu(i) {
  95                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
  96
  97                 b->last_task = NULL;
  98                 b->last_is_kernel = -1;
  99                 b->tracing = 0;
 100                 b->buffer_size = buffer_size;
 101                 b->sample_received = 0;
 102                 b->sample_lost_overflow = 0;
 103                 b->backtrace_aborted = 0;
 104                 b->sample_invalid_eip = 0;
 105                 b->cpu = i;
 106                 INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
 107         }
 108         return 0;
 109
 110 fail:
 111         free_cpu_buffers();
 112         return -ENOMEM;
 113 }
 114
 115 void start_cpu_work(void)
 116 {
 117         int i;
 118
 119         work_enabled = 1;
 120
 121         for_each_online_cpu(i) {
 122                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
 123
 124                 /*
 125                  * Spread the work by 1 jiffy per cpu so they dont all
 126                  * fire at once.
 127                  */
 128                 schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
 129         }
 130 }
 131
 132 void end_cpu_work(void)
 133 {
 134         int i;
 135
 136         work_enabled = 0;
 137
 138         for_each_online_cpu(i) {
 139                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
 140
 141                 cancel_delayed_work(&b->work);
 142         }
 143
 144         flush_scheduled_work();
 145 }
 146
 147 /*
 148  * This function prepares the cpu buffer to write a sample.
 149  *
 150  * Struct op_entry is used during operations on the ring buffer while
 151  * struct op_sample contains the data that is stored in the ring
 152  * buffer. Struct entry can be uninitialized. The function reserves a
 153  * data array that is specified by size. Use
 154  * op_cpu_buffer_write_commit() after preparing the sample. In case of
 155  * errors a null pointer is returned, otherwise the pointer to the
 156  * sample.
 157  *
 158  */
 159 struct op_sample
 160 *op_cpu_buffer_write_reserve(struct op_entry *entry, unsigned long size)
 161 {
 162         entry->event = ring_buffer_lock_reserve
 163                 (op_ring_buffer_write, sizeof(struct op_sample) +
 164                  size * sizeof(entry->sample->data[0]), &entry->irq_flags);
 165         if (entry->event)
 166                 entry->sample = ring_buffer_event_data(entry->event);
 167         else
 168                 entry->sample = NULL;
 169
 170         if (!entry->sample)
 171                 return NULL;
 172
 173         entry->size = size;
 174         entry->data = entry->sample->data;
 175
 176         return entry->sample;
 177 }
 178
 179 int op_cpu_buffer_write_commit(struct op_entry *entry)
 180 {
 181         return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event,
 182                                          entry->irq_flags);
 183 }
 184
 185 struct op_sample *op_cpu_buffer_read_entry(int cpu)
 186 {
 187         struct ring_buffer_event *e;
 188         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
 189         if (e)
 190                 return ring_buffer_event_data(e);
 191         if (ring_buffer_swap_cpu(op_ring_buffer_read,
 192                                  op_ring_buffer_write,
 193                                  cpu))
 194                 return NULL;
 195         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
 196         if (e)
 197                 return ring_buffer_event_data(e);
 198         return NULL;
 199 }
 200
 201 unsigned long op_cpu_buffer_entries(int cpu)
 202 {
 203         return ring_buffer_entries_cpu(op_ring_buffer_read, cpu)
 204                 + ring_buffer_entries_cpu(op_ring_buffer_write, cpu);
 205 }
 206
 207 static inline int
 208 op_add_sample(struct oprofile_cpu_buffer *cpu_buf,
 209               unsigned long pc, unsigned long event)
 210 {
 211         struct op_entry entry;
 212         struct op_sample *sample;
 213
 214         sample = op_cpu_buffer_write_reserve(&entry, 0);
 215         if (!sample)
 216                 return -ENOMEM;
 217
 218         sample->eip = pc;
 219         sample->event = event;
 220
 221         return op_cpu_buffer_write_commit(&entry);
 222 }
 223
 224 static inline int
 225 add_code(struct oprofile_cpu_buffer *buffer, unsigned long value)
 226 {
 227         return op_add_sample(buffer, ESCAPE_CODE, value);
 228 }
 229
 230 /* This must be safe from any context. It's safe writing here
 231  * because of the head/tail separation of the writer and reader
 232  * of the CPU buffer.
 233  *
 234  * is_kernel is needed because on some architectures you cannot
 235  * tell if you are in kernel or user space simply by looking at
 236  * pc. We tag this in the buffer by generating kernel enter/exit
 237  * events whenever is_kernel changes
 238  */
 239 static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
 240                       int is_kernel, unsigned long event)
 241 {
 242         struct task_struct *task;
 243
 244         cpu_buf->sample_received++;
 245
 246         if (pc == ESCAPE_CODE) {
 247                 cpu_buf->sample_invalid_eip++;
 248                 return 0;
 249         }
 250
 251         is_kernel = !!is_kernel;
 252
 253         task = current;
 254
 255         /* notice a switch from user->kernel or vice versa */
 256         if (cpu_buf->last_is_kernel != is_kernel) {
 257                 cpu_buf->last_is_kernel = is_kernel;
 258                 if (add_code(cpu_buf, is_kernel))
 259                         goto fail;
 260         }
 261
 262         /* notice a task switch */
 263         if (cpu_buf->last_task != task) {
 264                 cpu_buf->last_task = task;
 265                 if (add_code(cpu_buf, (unsigned long)task))
 266                         goto fail;
 267         }
 268
 269         if (op_add_sample(cpu_buf, pc, event))
 270                 goto fail;
 271
 272         return 1;
 273
 274 fail:
 275         cpu_buf->sample_lost_overflow++;
 276         return 0;
 277 }
 278
 279 static inline void oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
 280 {
 281         add_code(cpu_buf, CPU_TRACE_BEGIN);
 282         cpu_buf->tracing = 1;
 283 }
 284
 285 static inline void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf)
 286 {
 287         cpu_buf->tracing = 0;
 288 }
 289
 290 static inline void
 291 __oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
 292                           unsigned long event, int is_kernel)
 293 {
 294         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
 295
 296         if (!oprofile_backtrace_depth) {
 297                 log_sample(cpu_buf, pc, is_kernel, event);
 298                 return;
 299         }
 300
 301         oprofile_begin_trace(cpu_buf);
 302
 303         /*
 304          * if log_sample() fail we can't backtrace since we lost the
 305          * source of this event
 306          */
 307         if (log_sample(cpu_buf, pc, is_kernel, event))
 308                 oprofile_ops.backtrace(regs, oprofile_backtrace_depth);
 309
 310         oprofile_end_trace(cpu_buf);
 311 }
 312
 313 void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
 314                              unsigned long event, int is_kernel)
 315 {
 316         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
 317 }
 318
 319 void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
 320 {
 321         int is_kernel = !user_mode(regs);
 322         unsigned long pc = profile_pc(regs);
 323
 324         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
 325 }
 326
 327 #ifdef CONFIG_OPROFILE_IBS
 328
 329 void oprofile_add_ibs_sample(struct pt_regs * const regs,
 330                              unsigned int * const ibs_sample, int ibs_code)
 331 {
 332         int is_kernel = !user_mode(regs);
 333         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
 334         struct task_struct *task;
 335         int fail = 0;
 336
 337         cpu_buf->sample_received++;
 338
 339         /* notice a switch from user->kernel or vice versa */
 340         if (cpu_buf->last_is_kernel != is_kernel) {
 341                 if (add_code(cpu_buf, is_kernel))
 342                         goto fail;
 343                 cpu_buf->last_is_kernel = is_kernel;
 344         }
 345
 346         /* notice a task switch */
 347         if (!is_kernel) {
 348                 task = current;
 349                 if (cpu_buf->last_task != task) {
 350                         if (add_code(cpu_buf, (unsigned long)task))
 351                                 goto fail;
 352                         cpu_buf->last_task = task;
 353                 }
 354         }
 355
 356         fail = fail || add_code(cpu_buf, ibs_code);
 357         fail = fail || op_add_sample(cpu_buf, ibs_sample[0], ibs_sample[1]);
 358         fail = fail || op_add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]);
 359         fail = fail || op_add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]);
 360
 361         if (ibs_code == IBS_OP_BEGIN) {
 362                 fail = fail || op_add_sample(cpu_buf, ibs_sample[6], ibs_sample[7]);
 363                 fail = fail || op_add_sample(cpu_buf, ibs_sample[8], ibs_sample[9]);
 364                 fail = fail || op_add_sample(cpu_buf, ibs_sample[10], ibs_sample[11]);
 365         }
 366
 367         if (!fail)
 368                 return;
 369
 370 fail:
 371         cpu_buf->sample_lost_overflow++;
 372 }
 373
 374 #endif
 375
 376 void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
 377 {
 378         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
 379         log_sample(cpu_buf, pc, is_kernel, event);
 380 }
 381
 382 void oprofile_add_trace(unsigned long pc)
 383 {
 384         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
 385
 386         if (!cpu_buf->tracing)
 387                 return;
 388
 389         /*
 390          * broken frame can give an eip with the same value as an
 391          * escape code, abort the trace if we get it
 392          */
 393         if (pc == ESCAPE_CODE)
 394                 goto fail;
 395
 396         if (op_add_sample(cpu_buf, pc, 0))
 397                 goto fail;
 398
 399         return;
 400 fail:
 401         cpu_buf->tracing = 0;
 402         cpu_buf->backtrace_aborted++;
 403         return;
 404 }
 405
 406 /*
 407  * This serves to avoid cpu buffer overflow, and makes sure
 408  * the task mortuary progresses
 409  *
 410  * By using schedule_delayed_work_on and then schedule_delayed_work
 411  * we guarantee this will stay on the correct cpu
 412  */
 413 static void wq_sync_buffer(struct work_struct *work)
 414 {
 415         struct oprofile_cpu_buffer *b =
 416                 container_of(work, struct oprofile_cpu_buffer, work.work);
 417         if (b->cpu != smp_processor_id()) {
 418                 printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
 419                        smp_processor_id(), b->cpu);
 420
 421                 if (!cpu_online(b->cpu)) {
 422                         cancel_delayed_work(&b->work);
 423                         return;
 424                 }
 425         }
 426         sync_buffer(b->cpu);
 427
 428         /* don't re-add the work if we're shutting down */
 429         if (work_enabled)
 430                 schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
 431 }