File: DESIGN-barrier.txt

package info (click to toggle)
glibc 2.19-18+deb8u7
  • links: PTS, VCS
  • area: main
  • in suites: jessie-backports
  • size: 204,748 kB
  • sloc: ansic: 970,427; asm: 241,207; sh: 10,069; makefile: 8,476; cpp: 3,595; perl: 2,077; pascal: 1,839; awk: 1,704; yacc: 317; sed: 73
file content (44 lines) | stat: -rw-r--r-- 938 bytes parent folder | download | duplicates (45)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
Barriers pseudocode
===================

    int pthread_barrier_wait(barrier_t *barrier);

struct barrier_t {

   unsigned int lock:
         - internal mutex

   unsigned int left;
         - current barrier count, # of threads still needed.

   unsigned int init_count;
         - number of threads needed for the barrier to continue.

   unsigned int curr_event;
         - generation count
}

pthread_barrier_wait(barrier_t *barrier)
{
  unsigned int event;
  result = 0;

  lll_lock(barrier->lock);
  if (!--barrier->left) {
    barrier->curr_event++;
    futex_wake(&barrier->curr_event, INT_MAX)

    result = BARRIER_SERIAL_THREAD;
  } else {
    event = barrier->curr_event;
    lll_unlock(barrier->lock);
    do {
      futex_wait(&barrier->curr_event, event)
    } while (event == barrier->curr_event);
  }

  if (atomic_increment_val (barrier->left) == barrier->init_count)
    lll_unlock(barrier->lock);

  return result;
}