include/linux/ptr_ring.h

   1 /*
   2  *      Definitions for the 'struct ptr_ring' datastructure.
   3  *
   4  *      Author:
   5  *              Michael S. Tsirkin <mst@redhat.com>
   6  *
   7  *      Copyright (C) 2016 Red Hat, Inc.
   8  *
   9  *      This program is free software; you can redistribute it and/or modify it
  10  *      under the terms of the GNU General Public License as published by the
  11  *      Free Software Foundation; either version 2 of the License, or (at your
  12  *      option) any later version.
  13  *
  14  *      This is a limited-size FIFO maintaining pointers in FIFO order, with
  15  *      one CPU producing entries and another consuming entries from a FIFO.
  16  *
  17  *      This implementation tries to minimize cache-contention when there is a
  18  *      single producer and a single consumer CPU.
  19  */
  20
  21 #ifndef _LINUX_PTR_RING_H
  22 #define _LINUX_PTR_RING_H 1
  23
  24 #ifdef __KERNEL__
  25 #include <linux/spinlock.h>
  26 #include <linux/cache.h>
  27 #include <linux/types.h>
  28 #include <linux/compiler.h>
  29 #include <linux/cache.h>
  30 #include <linux/slab.h>
  31 #include <asm/errno.h>
  32 #endif
  33
  34 struct ptr_ring {
  35         int producer ____cacheline_aligned_in_smp;
  36         spinlock_t producer_lock;
  37         int consumer ____cacheline_aligned_in_smp;
  38         spinlock_t consumer_lock;
  39         /* Shared consumer/producer data */
  40         /* Read-only by both the producer and the consumer */
  41         int size ____cacheline_aligned_in_smp; /* max entries in queue */
  42         void **queue;
  43 };
  44
  45 /* Note: callers invoking this in a loop must use a compiler barrier,
  46  * for example cpu_relax().  If ring is ever resized, callers must hold
  47  * producer_lock - see e.g. ptr_ring_full.  Otherwise, if callers don't hold
  48  * producer_lock, the next call to __ptr_ring_produce may fail.
  49  */
  50 static inline bool __ptr_ring_full(struct ptr_ring *r)
  51 {
  52         return r->queue[r->producer];
  53 }
  54
  55 static inline bool ptr_ring_full(struct ptr_ring *r)
  56 {
  57         bool ret;
  58
  59         spin_lock(&r->producer_lock);
  60         ret = __ptr_ring_full(r);
  61         spin_unlock(&r->producer_lock);
  62
  63         return ret;
  64 }
  65
  66 static inline bool ptr_ring_full_irq(struct ptr_ring *r)
  67 {
  68         bool ret;
  69
  70         spin_lock_irq(&r->producer_lock);
  71         ret = __ptr_ring_full(r);
  72         spin_unlock_irq(&r->producer_lock);
  73
  74         return ret;
  75 }
  76
  77 static inline bool ptr_ring_full_any(struct ptr_ring *r)
  78 {
  79         unsigned long flags;
  80         bool ret;
  81
  82         spin_lock_irqsave(&r->producer_lock, flags);
  83         ret = __ptr_ring_full(r);
  84         spin_unlock_irqrestore(&r->producer_lock, flags);
  85
  86         return ret;
  87 }
  88
  89 static inline bool ptr_ring_full_bh(struct ptr_ring *r)
  90 {
  91         bool ret;
  92
  93         spin_lock_bh(&r->producer_lock);
  94         ret = __ptr_ring_full(r);
  95         spin_unlock_bh(&r->producer_lock);
  96
  97         return ret;
  98 }
  99
 100 /* Note: callers invoking this in a loop must use a compiler barrier,
 101  * for example cpu_relax(). Callers must hold producer_lock.
 102  */
 103 static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr)
 104 {
 105         if (unlikely(!r->size) || r->queue[r->producer])
 106                 return -ENOSPC;
 107
 108         r->queue[r->producer++] = ptr;
 109         if (unlikely(r->producer >= r->size))
 110                 r->producer = 0;
 111         return 0;
 112 }
 113
 114 static inline int ptr_ring_produce(struct ptr_ring *r, void *ptr)
 115 {
 116         int ret;
 117
 118         spin_lock(&r->producer_lock);
 119         ret = __ptr_ring_produce(r, ptr);
 120         spin_unlock(&r->producer_lock);
 121
 122         return ret;
 123 }
 124
 125 static inline int ptr_ring_produce_irq(struct ptr_ring *r, void *ptr)
 126 {
 127         int ret;
 128
 129         spin_lock_irq(&r->producer_lock);
 130         ret = __ptr_ring_produce(r, ptr);
 131         spin_unlock_irq(&r->producer_lock);
 132
 133         return ret;
 134 }
 135
 136 static inline int ptr_ring_produce_any(struct ptr_ring *r, void *ptr)
 137 {
 138         unsigned long flags;
 139         int ret;
 140
 141         spin_lock_irqsave(&r->producer_lock, flags);
 142         ret = __ptr_ring_produce(r, ptr);
 143         spin_unlock_irqrestore(&r->producer_lock, flags);
 144
 145         return ret;
 146 }
 147
 148 static inline int ptr_ring_produce_bh(struct ptr_ring *r, void *ptr)
 149 {
 150         int ret;
 151
 152         spin_lock_bh(&r->producer_lock);
 153         ret = __ptr_ring_produce(r, ptr);
 154         spin_unlock_bh(&r->producer_lock);
 155
 156         return ret;
 157 }
 158
 159 /* Note: callers invoking this in a loop must use a compiler barrier,
 160  * for example cpu_relax(). Callers must take consumer_lock
 161  * if they dereference the pointer - see e.g. PTR_RING_PEEK_CALL.
 162  * If ring is never resized, and if the pointer is merely
 163  * tested, there's no need to take the lock - see e.g.  __ptr_ring_empty.
 164  */
 165 static inline void *__ptr_ring_peek(struct ptr_ring *r)
 166 {
 167         if (likely(r->size))
 168                 return r->queue[r->consumer];
 169         return NULL;
 170 }
 171
 172 /* Note: callers invoking this in a loop must use a compiler barrier,
 173  * for example cpu_relax(). Callers must take consumer_lock
 174  * if the ring is ever resized - see e.g. ptr_ring_empty.
 175  */
 176 static inline bool __ptr_ring_empty(struct ptr_ring *r)
 177 {
 178         return !__ptr_ring_peek(r);
 179 }
 180
 181 static inline bool ptr_ring_empty(struct ptr_ring *r)
 182 {
 183         bool ret;
 184
 185         spin_lock(&r->consumer_lock);
 186         ret = __ptr_ring_empty(r);
 187         spin_unlock(&r->consumer_lock);
 188
 189         return ret;
 190 }
 191
 192 static inline bool ptr_ring_empty_irq(struct ptr_ring *r)
 193 {
 194         bool ret;
 195
 196         spin_lock_irq(&r->consumer_lock);
 197         ret = __ptr_ring_empty(r);
 198         spin_unlock_irq(&r->consumer_lock);
 199
 200         return ret;
 201 }
 202
 203 static inline bool ptr_ring_empty_any(struct ptr_ring *r)
 204 {
 205         unsigned long flags;
 206         bool ret;
 207
 208         spin_lock_irqsave(&r->consumer_lock, flags);
 209         ret = __ptr_ring_empty(r);
 210         spin_unlock_irqrestore(&r->consumer_lock, flags);
 211
 212         return ret;
 213 }
 214
 215 static inline bool ptr_ring_empty_bh(struct ptr_ring *r)
 216 {
 217         bool ret;
 218
 219         spin_lock_bh(&r->consumer_lock);
 220         ret = __ptr_ring_empty(r);
 221         spin_unlock_bh(&r->consumer_lock);
 222
 223         return ret;
 224 }
 225
 226 /* Must only be called after __ptr_ring_peek returned !NULL */
 227 static inline void __ptr_ring_discard_one(struct ptr_ring *r)
 228 {
 229         r->queue[r->consumer++] = NULL;
 230         if (unlikely(r->consumer >= r->size))
 231                 r->consumer = 0;
 232 }
 233
 234 static inline void *__ptr_ring_consume(struct ptr_ring *r)
 235 {
 236         void *ptr;
 237
 238         ptr = __ptr_ring_peek(r);
 239         if (ptr)
 240                 __ptr_ring_discard_one(r);
 241
 242         return ptr;
 243 }
 244
 245 static inline void *ptr_ring_consume(struct ptr_ring *r)
 246 {
 247         void *ptr;
 248
 249         spin_lock(&r->consumer_lock);
 250         ptr = __ptr_ring_consume(r);
 251         spin_unlock(&r->consumer_lock);
 252
 253         return ptr;
 254 }
 255
 256 static inline void *ptr_ring_consume_irq(struct ptr_ring *r)
 257 {
 258         void *ptr;
 259
 260         spin_lock_irq(&r->consumer_lock);
 261         ptr = __ptr_ring_consume(r);
 262         spin_unlock_irq(&r->consumer_lock);
 263
 264         return ptr;
 265 }
 266
 267 static inline void *ptr_ring_consume_any(struct ptr_ring *r)
 268 {
 269         unsigned long flags;
 270         void *ptr;
 271
 272         spin_lock_irqsave(&r->consumer_lock, flags);
 273         ptr = __ptr_ring_consume(r);
 274         spin_unlock_irqrestore(&r->consumer_lock, flags);
 275
 276         return ptr;
 277 }
 278
 279 static inline void *ptr_ring_consume_bh(struct ptr_ring *r)
 280 {
 281         void *ptr;
 282
 283         spin_lock_bh(&r->consumer_lock);
 284         ptr = __ptr_ring_consume(r);
 285         spin_unlock_bh(&r->consumer_lock);
 286
 287         return ptr;
 288 }
 289
 290 /* Cast to structure type and call a function without discarding from FIFO.
 291  * Function must return a value.
 292  * Callers must take consumer_lock.
 293  */
 294 #define __PTR_RING_PEEK_CALL(r, f) ((f)(__ptr_ring_peek(r)))
 295
 296 #define PTR_RING_PEEK_CALL(r, f) ({ \
 297         typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \
 298         \
 299         spin_lock(&(r)->consumer_lock); \
 300         __PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \
 301         spin_unlock(&(r)->consumer_lock); \
 302         __PTR_RING_PEEK_CALL_v; \
 303 })
 304
 305 #define PTR_RING_PEEK_CALL_IRQ(r, f) ({ \
 306         typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \
 307         \
 308         spin_lock_irq(&(r)->consumer_lock); \
 309         __PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \
 310         spin_unlock_irq(&(r)->consumer_lock); \
 311         __PTR_RING_PEEK_CALL_v; \
 312 })
 313
 314 #define PTR_RING_PEEK_CALL_BH(r, f) ({ \
 315         typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \
 316         \
 317         spin_lock_bh(&(r)->consumer_lock); \
 318         __PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \
 319         spin_unlock_bh(&(r)->consumer_lock); \
 320         __PTR_RING_PEEK_CALL_v; \
 321 })
 322
 323 #define PTR_RING_PEEK_CALL_ANY(r, f) ({ \
 324         typeof((f)(NULL)) __PTR_RING_PEEK_CALL_v; \
 325         unsigned long __PTR_RING_PEEK_CALL_f;\
 326         \
 327         spin_lock_irqsave(&(r)->consumer_lock, __PTR_RING_PEEK_CALL_f); \
 328         __PTR_RING_PEEK_CALL_v = __PTR_RING_PEEK_CALL(r, f); \
 329         spin_unlock_irqrestore(&(r)->consumer_lock, __PTR_RING_PEEK_CALL_f); \
 330         __PTR_RING_PEEK_CALL_v; \
 331 })
 332
 333 static inline void **__ptr_ring_init_queue_alloc(int size, gfp_t gfp)
 334 {
 335         return kzalloc(ALIGN(size * sizeof(void *), SMP_CACHE_BYTES), gfp);
 336 }
 337
 338 static inline int ptr_ring_init(struct ptr_ring *r, int size, gfp_t gfp)
 339 {
 340         r->queue = __ptr_ring_init_queue_alloc(size, gfp);
 341         if (!r->queue)
 342                 return -ENOMEM;
 343
 344         r->size = size;
 345         r->producer = r->consumer = 0;
 346         spin_lock_init(&r->producer_lock);
 347         spin_lock_init(&r->consumer_lock);
 348
 349         return 0;
 350 }
 351
 352 static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void **queue,
 353                                            int size, gfp_t gfp,
 354                                            void (*destroy)(void *))
 355 {
 356         int producer = 0;
 357         void **old;
 358         void *ptr;
 359
 360         while ((ptr = ptr_ring_consume(r)))
 361                 if (producer < size)
 362                         queue[producer++] = ptr;
 363                 else if (destroy)
 364                         destroy(ptr);
 365
 366         r->size = size;
 367         r->producer = producer;
 368         r->consumer = 0;
 369         old = r->queue;
 370         r->queue = queue;
 371
 372         return old;
 373 }
 374
 375 static inline int ptr_ring_resize(struct ptr_ring *r, int size, gfp_t gfp,
 376                                   void (*destroy)(void *))
 377 {
 378         unsigned long flags;
 379         void **queue = __ptr_ring_init_queue_alloc(size, gfp);
 380         void **old;
 381
 382         if (!queue)
 383                 return -ENOMEM;
 384
 385         spin_lock_irqsave(&(r)->producer_lock, flags);
 386
 387         old = __ptr_ring_swap_queue(r, queue, size, gfp, destroy);
 388
 389         spin_unlock_irqrestore(&(r)->producer_lock, flags);
 390
 391         kfree(old);
 392
 393         return 0;
 394 }
 395
 396 static inline int ptr_ring_resize_multiple(struct ptr_ring **rings, int nrings,
 397                                            int size,
 398                                            gfp_t gfp, void (*destroy)(void *))
 399 {
 400         unsigned long flags;
 401         void ***queues;
 402         int i;
 403
 404         queues = kmalloc(nrings * sizeof *queues, gfp);
 405         if (!queues)
 406                 goto noqueues;
 407
 408         for (i = 0; i < nrings; ++i) {
 409                 queues[i] = __ptr_ring_init_queue_alloc(size, gfp);
 410                 if (!queues[i])
 411                         goto nomem;
 412         }
 413
 414         for (i = 0; i < nrings; ++i) {
 415                 spin_lock_irqsave(&(rings[i])->producer_lock, flags);
 416                 queues[i] = __ptr_ring_swap_queue(rings[i], queues[i],
 417                                                   size, gfp, destroy);
 418                 spin_unlock_irqrestore(&(rings[i])->producer_lock, flags);
 419         }
 420
 421         for (i = 0; i < nrings; ++i)
 422                 kfree(queues[i]);
 423
 424         kfree(queues);
 425
 426         return 0;
 427
 428 nomem:
 429         while (--i >= 0)
 430                 kfree(queues[i]);
 431
 432         kfree(queues);
 433
 434 noqueues:
 435         return -ENOMEM;
 436 }
 437
 438 static inline void ptr_ring_cleanup(struct ptr_ring *r, void (*destroy)(void *))
 439 {
 440         void *ptr;
 441
 442         if (destroy)
 443                 while ((ptr = ptr_ring_consume(r)))
 444                         destroy(ptr);
 445         kfree(r->queue);
 446 }
 447
 448 #endif /* _LINUX_PTR_RING_H  */