libust/ltt-context.c

   1 /*
   2  * ltt-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 "ltt-events.h"
  17 #include "ltt-tracer.h"
  18
  19 /*
  20  * Note: as we append context information, the pointer location may change.
  21  */
  22 struct lttng_ctx_field *lttng_append_context(struct lttng_ctx **ctx_p)
  23 {
  24         struct lttng_ctx_field *field;
  25         struct lttng_ctx *ctx;
  26
  27         if (!*ctx_p) {
  28                 *ctx_p = kzalloc(sizeof(struct lttng_ctx), GFP_KERNEL);
  29                 if (!*ctx_p)
  30                         return NULL;
  31         }
  32         ctx = *ctx_p;
  33         if (ctx->nr_fields + 1 > ctx->allocated_fields) {
  34                 struct lttng_ctx_field *new_fields;
  35
  36                 ctx->allocated_fields = max_t(size_t, 1, 2 * ctx->allocated_fields);
  37                 new_fields = kzalloc(ctx->allocated_fields * sizeof(struct lttng_ctx_field), GFP_KERNEL);
  38                 if (!new_fields)
  39                         return NULL;
  40                 if (ctx->fields)
  41                         memcpy(new_fields, ctx->fields, sizeof(*ctx->fields) * ctx->nr_fields);
  42                 kfree(ctx->fields);
  43                 ctx->fields = new_fields;
  44         }
  45         field = &ctx->fields[ctx->nr_fields];
  46         ctx->nr_fields++;
  47         return field;
  48 }
  49 EXPORT_SYMBOL_GPL(lttng_append_context);
  50
  51 /*
  52  * Remove last context field.
  53  */
  54 void lttng_remove_context_field(struct lttng_ctx **ctx_p,
  55                                 struct lttng_ctx_field *field)
  56 {
  57         struct lttng_ctx *ctx;
  58
  59         ctx = *ctx_p;
  60         ctx->nr_fields--;
  61         WARN_ON_ONCE(&ctx->fields[ctx->nr_fields] != field);
  62         memset(&ctx->fields[ctx->nr_fields], 0, sizeof(struct lttng_ctx_field));
  63 }
  64 EXPORT_SYMBOL_GPL(lttng_remove_context_field);
  65
  66 void lttng_destroy_context(struct lttng_ctx *ctx)
  67 {
  68         int i;
  69
  70         if (!ctx)
  71                 return;
  72         for (i = 0; i < ctx->nr_fields; i++) {
  73                 if (ctx->fields[i].destroy)
  74                         ctx->fields[i].destroy(&ctx->fields[i]);
  75         }
  76         kfree(ctx->fields);
  77         kfree(ctx);
  78 }