src/lttng-context-prio.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-context-prio.c
   4  *
   5  * LTTng priority 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 #include <lttng/kernel-version.h>
  19
  20 /*
  21  * From kernel v3.0 to v3.8, MAX_RT_PRIO is defined in linux/sched.h.
  22  * From kernel v3.9 to v3.14, MAX_RT_PRIO is defined in linux/sched/rt.h,
  23  * which is not included by linux/sched.h (hence this work-around).
  24  * From kernel v3.15 onwards, MAX_RT_PRIO is defined in linux/sched/prio.h,
  25  * which is included by linux/sched.h.
  26  */
  27 #if LTTNG_KERNEL_RANGE(3,9,0, 3,15,0)
  28 # include <linux/sched/rt.h>
  29 #endif
  30
  31 /*
  32  * task_prio() has been implemented as p->prio - MAX_RT_PRIO since at
  33  * least kernel v3.0.
  34  */
  35 static
  36 int wrapper_task_prio(struct task_struct *p)
  37 {
  38         return p->prio - MAX_RT_PRIO;
  39 }
  40
  41 static
  42 size_t prio_get_size(void *priv, struct lttng_kernel_probe_ctx *probe_ctx, size_t offset)
  43 {
  44         size_t size = 0;
  45
  46         size += lib_ring_buffer_align(offset, lttng_alignof(int));
  47         size += sizeof(int);
  48         return size;
  49 }
  50
  51 static
  52 void prio_record(void *priv, struct lttng_kernel_probe_ctx *probe_ctx,
  53                 struct lttng_kernel_ring_buffer_ctx *ctx,
  54                 struct lttng_kernel_channel_buffer *chan)
  55 {
  56         int prio;
  57
  58         prio = wrapper_task_prio(current);
  59         chan->ops->event_write(ctx, &prio, sizeof(prio), lttng_alignof(prio));
  60 }
  61
  62 static
  63 void prio_get_value(void *priv,
  64                 struct lttng_kernel_probe_ctx *lttng_probe_ctx,
  65                 struct lttng_ctx_value *value)
  66 {
  67         value->u.s64 = wrapper_task_prio(current);
  68 }
  69
  70 static const struct lttng_kernel_ctx_field *ctx_field = lttng_kernel_static_ctx_field(
  71         lttng_kernel_static_event_field("prio",
  72                 lttng_kernel_static_type_integer_from_type(int, __BYTE_ORDER, 10),
  73                 false, false),
  74         prio_get_size,
  75         prio_record,
  76         prio_get_value,
  77         NULL, NULL);
  78
  79 int lttng_add_prio_to_ctx(struct lttng_kernel_ctx **ctx)
  80 {
  81         int ret;
  82
  83         if (lttng_kernel_find_context(*ctx, ctx_field->event_field->name))
  84                 return -EEXIST;
  85         ret = lttng_kernel_context_append(ctx, ctx_field);
  86         wrapper_vmalloc_sync_mappings();
  87         return ret;
  88 }
  89 EXPORT_SYMBOL_GPL(lttng_add_prio_to_ctx);