lttng-context.c

   1 /*
   2  * lttng-context.c
   3  *
   4  * LTTng trace/channel/event context management.
   5  *
   6  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/list.h>
  25 #include <linux/mutex.h>
  26 #include <linux/slab.h>
  27 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  28 #include "lttng-events.h"
  29 #include "lttng-tracer.h"
  30
  31 int lttng_find_context(struct lttng_ctx *ctx, const char *name)
  32 {
  33         unsigned int i;
  34
  35         for (i = 0; i < ctx->nr_fields; i++) {
  36                 /* Skip allocated (but non-initialized) contexts */
  37                 if (!ctx->fields[i].event_field.name)
  38                         continue;
  39                 if (!strcmp(ctx->fields[i].event_field.name, name))
  40                         return 1;
  41         }
  42         return 0;
  43 }
  44 EXPORT_SYMBOL_GPL(lttng_find_context);
  45
  46 /*
  47  * Note: as we append context information, the pointer location may change.
  48  */
  49 struct lttng_ctx_field *lttng_append_context(struct lttng_ctx **ctx_p)
  50 {
  51         struct lttng_ctx_field *field;
  52         struct lttng_ctx *ctx;
  53
  54         if (!*ctx_p) {
  55                 *ctx_p = kzalloc(sizeof(struct lttng_ctx), GFP_KERNEL);
  56                 if (!*ctx_p)
  57                         return NULL;
  58         }
  59         ctx = *ctx_p;
  60         if (ctx->nr_fields + 1 > ctx->allocated_fields) {
  61                 struct lttng_ctx_field *new_fields;
  62
  63                 ctx->allocated_fields = max_t(size_t, 1, 2 * ctx->allocated_fields);
  64                 new_fields = kzalloc(ctx->allocated_fields * sizeof(struct lttng_ctx_field), GFP_KERNEL);
  65                 if (!new_fields)
  66                         return NULL;
  67                 if (ctx->fields)
  68                         memcpy(new_fields, ctx->fields, sizeof(*ctx->fields) * ctx->nr_fields);
  69                 kfree(ctx->fields);
  70                 ctx->fields = new_fields;
  71         }
  72         field = &ctx->fields[ctx->nr_fields];
  73         ctx->nr_fields++;
  74         return field;
  75 }
  76 EXPORT_SYMBOL_GPL(lttng_append_context);
  77
  78 /*
  79  * Remove last context field.
  80  */
  81 void lttng_remove_context_field(struct lttng_ctx **ctx_p,
  82                                 struct lttng_ctx_field *field)
  83 {
  84         struct lttng_ctx *ctx;
  85
  86         ctx = *ctx_p;
  87         ctx->nr_fields--;
  88         WARN_ON_ONCE(&ctx->fields[ctx->nr_fields] != field);
  89         memset(&ctx->fields[ctx->nr_fields], 0, sizeof(struct lttng_ctx_field));
  90 }
  91 EXPORT_SYMBOL_GPL(lttng_remove_context_field);
  92
  93 void lttng_destroy_context(struct lttng_ctx *ctx)
  94 {
  95         int i;
  96
  97         if (!ctx)
  98                 return;
  99         for (i = 0; i < ctx->nr_fields; i++) {
 100                 if (ctx->fields[i].destroy)
 101                         ctx->fields[i].destroy(&ctx->fields[i]);
 102         }
 103         kfree(ctx->fields);
 104         kfree(ctx);
 105 }