Channels ▼

Open Source

Soft Real-Time Programming with Linux

November, 2005: Soft Real-Time Programming with Linux

Listing 1

#include <pthread.h>

pid_t child_pid;
struct sched_param old_param;
struct pthread_mutex_t mutex;

void raise_child_priority()
  struct sched_param current;

  // Get the priority of the current thread
  sched_getparam(0, &current);

  // Get the priority of the child thread
  sched_getparam(child_pid, &old_param);

  // If the current thread's priority is greater than the
  // child's priority, raise the child's priority
  if(current.sched_priority > old_param.sched_priority) {
    sched_setparam(child_pid, &current);

void lower_child_priority()
  // Set the child thread's priority back to its old priority
  sched_setparam(child_pid, &old_param);

int access_shared_resource()
  // First, try to get a lock on the resource
  if(pthread_mutex_trylock(&mutex) < 0) {
    if(errno == EBUSY) {
      // The other thread has the resource, 
      // raise its priority then perform a blocking lock
      if(pthread_mutex_lock(&mutex) < 0) return -1;
    else {
      return -1;

  // Lower the child's priority back to normal

  /* Do stuff with the locked resource */

  // Release the lock
  if(pthread_mutex_unlock(&lock) < 0) return -1;
  return 0;

Related Reading

More Insights

Currently we allow the following HTML tags in comments:

Single tags

These tags can be used alone and don't need an ending tag.

<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags

These require an ending tag - e.g. <i>italic text</i>

<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

Dr. Dobb's encourages readers to engage in spirited, healthy debate, including taking us to task. However, Dr. Dobb's moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing or spam. Dr. Dobb's further reserves the right to disable the profile of any commenter participating in said activities.

Disqus Tips To upload an avatar photo, first complete your Disqus profile. | View the list of supported HTML tags you can use to style comments. | Please read our commenting policy.