lttng-context.c

   1 /*
   2  * lttng-context.c
   3  *
   4  * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * LTTng trace/channel/event context management.
   7  *
   8  * Dual LGPL v2.1/GPL v2 license.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/list.h>
  13 #include <linux/mutex.h>
  14 #include <linux/slab.h>
  15 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  16 #include "lttng-events.h"
  17 #include "lttng-tracer.h"
  18
  19 int lttng_find_context(struct lttng_ctx *ctx, const char *name)
  20 {
  21         unsigned int i;
  22
  23         for (i = 0; i < ctx->nr_fields; i++) {
  24                 /* Skip allocated (but non-initialized) contexts */
  25                 if (!ctx->fields[i].event_field.name)
  26                         continue;
  27                 if (!strcmp(ctx->fields[i].event_field.name, name))
  28                         return 1;
  29         }
  30         return 0;
  31 }
  32 EXPORT_SYMBOL_GPL(lttng_find_context);
  33
  34 /*
  35  * Note: as we append context information, the pointer location may change.
  36  */
  37 struct lttng_ctx_field *lttng_append_context(struct lttng_ctx **ctx_p)
  38 {
  39         struct lttng_ctx_field *field;
  40         struct lttng_ctx *ctx;
  41
  42         if (!*ctx_p) {
  43                 *ctx_p = kzalloc(sizeof(struct lttng_ctx), GFP_KERNEL);
  44                 if (!*ctx_p)
  45                         return NULL;
  46         }
  47         ctx = *ctx_p;
  48         if (ctx->nr_fields + 1 > ctx->allocated_fields) {
  49                 struct lttng_ctx_field *new_fields;
  50
  51                 ctx->allocated_fields = max_t(size_t, 1, 2 * ctx->allocated_fields);
  52                 new_fields = kzalloc(ctx->allocated_fields * sizeof(struct lttng_ctx_field), GFP_KERNEL);
  53                 if (!new_fields)
  54                         return NULL;
  55                 if (ctx->fields)
  56                         memcpy(new_fields, ctx->fields, sizeof(*ctx->fields) * ctx->nr_fields);
  57                 kfree(ctx->fields);
  58                 ctx->fields = new_fields;
  59         }
  60         field = &ctx->fields[ctx->nr_fields];
  61         ctx->nr_fields++;
  62         return field;
  63 }
  64 EXPORT_SYMBOL_GPL(lttng_append_context);
  65
  66 /*
  67  * Remove last context field.
  68  */
  69 void lttng_remove_context_field(struct lttng_ctx **ctx_p,
  70                                 struct lttng_ctx_field *field)
  71 {
  72         struct lttng_ctx *ctx;
  73
  74         ctx = *ctx_p;
  75         ctx->nr_fields--;
  76         WARN_ON_ONCE(&ctx->fields[ctx->nr_fields] != field);
  77         memset(&ctx->fields[ctx->nr_fields], 0, sizeof(struct lttng_ctx_field));
  78 }
  79 EXPORT_SYMBOL_GPL(lttng_remove_context_field);
  80
  81 void lttng_destroy_context(struct lttng_ctx *ctx)
  82 {
  83         int i;
  84
  85         if (!ctx)
  86                 return;
  87         for (i = 0; i < ctx->nr_fields; i++) {
  88                 if (ctx->fields[i].destroy)
  89                         ctx->fields[i].destroy(&ctx->fields[i]);
  90         }
  91         kfree(ctx->fields);
  92         kfree(ctx);
  93 }