Uncancelable Critical Sections

• A thread may disable cancellation of itself altogether with the
  pthread_setcancelstate function. Like pthread_setcanceltype, this affects the calling thread.
  • The first argument is PTHREAD_CANCEL_DISABLE to disable cancellation, or PTHREAD_CANCEL_ENABLE to re-enable cancellation.
  • The second argument, if not null, points to a variable that will receive the previous cancellation state.

  pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, NULL);
  

• Using pthread_setcancelstate enables you to implement critical sections.
• If a thread begins executing the critical section, it must continue until the end of the critical section without being canceled. http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/critical-section.ccritical-section.c (see Fig. 5.6)

  Figure 5.6: Protect a Bank Transaction with a Critical Section

  
• Note that it s important to restore the old cancel state at the end of the critical section rather than setting it unconditionally to
  PTHREAD_CANCEL_ENABLE.