src/lttng-context-nice.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-nice.c
   4  *
   5  * LTTng nice context.
   6  *
   7  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <linux/sched.h>
  13 #include <lttng/events.h>
  14 #include <lttng/events-internal.h>
  15 #include <ringbuffer/frontend_types.h>
  16 #include <wrapper/vmalloc.h>
  17 #include <lttng/tracer.h>
  18
  19 static
  20 size_t nice_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  21 {
  22         size_t size = 0;
  23
  24         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  25         size += sizeof(int);
  26         return size;
  27 }
  28
  29 static
  30 void nice_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  31                 struct lttng_kernel_ring_buffer_ctx *ctx,
  32                 struct lttng_kernel_channel_buffer *chan)
  33 {
  34         int nice;
  35
  36         nice = task_nice(current);
  37         chan->ops->event_write(ctx, &nice, sizeof(nice), lttng_alignof(nice));
  38 }
  39
  40 static
  41 void nice_get_value(void *priv,
  42                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  43                 struct lttng_ctx_value *value)
  44 {
  45         value->u.s64 = task_nice(current);
  46 }
  47
  48 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  49         lttng_kernel_static_event_field("nice",
  50                 lttng_kernel_static_type_integer_from_type(int, __BYTE_ORDER, 10),
  51                 false, false),
  52         nice_get_size,
  53         nice_record,
  54         nice_get_value,
  55         NULL, NULL);
  56
  57 int lttng_add_nice_to_ctx(struct lttng_kernel_ctx **ctx)
  58 {
  59         int ret;
  60
  61         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  62                 return -EEXIST;
  63         ret = lttng_kernel_context_append(ctx, ctx_field);
  64         wrapper_vmalloc_sync_mappings();
  65         return ret;
  66 }
  67 EXPORT_SYMBOL_GPL(lttng_add_nice_to_ctx);