include/linux/percpu_ida.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __PERCPU_IDA_H__
   3 #define __PERCPU_IDA_H__
   4
   5 #include <linux/types.h>
   6 #include <linux/bitops.h>
   7 #include <linux/init.h>
   8 #include <linux/sched.h>
   9 #include <linux/spinlock_types.h>
  10 #include <linux/wait.h>
  11 #include <linux/cpumask.h>
  12
  13 struct percpu_ida_cpu;
  14
  15 struct percpu_ida {
  16         /*
  17          * number of tags available to be allocated, as passed to
  18          * percpu_ida_init()
  19          */
  20         unsigned                        nr_tags;
  21         unsigned                        percpu_max_size;
  22         unsigned                        percpu_batch_size;
  23
  24         struct percpu_ida_cpu __percpu  *tag_cpu;
  25
  26         /*
  27          * Bitmap of cpus that (may) have tags on their percpu freelists:
  28          * steal_tags() uses this to decide when to steal tags, and which cpus
  29          * to try stealing from.
  30          *
  31          * It's ok for a freelist to be empty when its bit is set - steal_tags()
  32          * will just keep looking - but the bitmap _must_ be set whenever a
  33          * percpu freelist does have tags.
  34          */
  35         cpumask_t                       cpus_have_tags;
  36
  37         struct {
  38                 spinlock_t              lock;
  39                 /*
  40                  * When we go to steal tags from another cpu (see steal_tags()),
  41                  * we want to pick a cpu at random. Cycling through them every
  42                  * time we steal is a bit easier and more or less equivalent:
  43                  */
  44                 unsigned                cpu_last_stolen;
  45
  46                 /* For sleeping on allocation failure */
  47                 wait_queue_head_t       wait;
  48
  49                 /*
  50                  * Global freelist - it's a stack where nr_free points to the
  51                  * top
  52                  */
  53                 unsigned                nr_free;
  54                 unsigned                *freelist;
  55         } ____cacheline_aligned_in_smp;
  56 };
  57
  58 /*
  59  * Number of tags we move between the percpu freelist and the global freelist at
  60  * a time
  61  */
  62 #define IDA_DEFAULT_PCPU_BATCH_MOVE     32U
  63 /* Max size of percpu freelist, */
  64 #define IDA_DEFAULT_PCPU_SIZE   ((IDA_DEFAULT_PCPU_BATCH_MOVE * 3) / 2)
  65
  66 int percpu_ida_alloc(struct percpu_ida *pool, int state);
  67 void percpu_ida_free(struct percpu_ida *pool, unsigned tag);
  68
  69 void percpu_ida_destroy(struct percpu_ida *pool);
  70 int __percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags,
  71         unsigned long max_size, unsigned long batch_size);
  72 static inline int percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags)
  73 {
  74         return __percpu_ida_init(pool, nr_tags, IDA_DEFAULT_PCPU_SIZE,
  75                 IDA_DEFAULT_PCPU_BATCH_MOVE);
  76 }
  77
  78 typedef int (*percpu_ida_cb)(unsigned, void *);
  79 int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
  80         void *data);
  81
  82 unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu);
  83 #endif /* __PERCPU_IDA_H__ */