test/testsem.c
author Sam Lantinga <slouken@libsdl.org>
Thu, 27 Jan 2011 00:33:26 -0800
branchSDL-1.2
changeset 5105 99acf3d856cb
parent 1769 290b5baf2fca
child 6297 c787fb1b5699
permissions -rw-r--r--
Colin Leroy 2011-01-26 04:24:20 PST

the pthread implementation of SDL_SemWaitTimeout() uses busy waiting, while
pthread's sem_timedwait() does work. Attached are patches that make use of it
     1 
     2 /* Simple test of the SDL semaphore code */
     3 
     4 #include <stdio.h>
     5 #include <stdlib.h>
     6 #include <signal.h>
     7 
     8 #include "SDL.h"
     9 #include "SDL_thread.h"
    10 
    11 #define NUM_THREADS 10
    12 
    13 static SDL_sem *sem;
    14 int alive = 1;
    15 
    16 int SDLCALL ThreadFunc(void *data)
    17 {
    18 	int threadnum = (int)(uintptr_t)data;
    19 	while ( alive ) {
    20 		SDL_SemWait(sem);
    21 		fprintf(stderr, "Thread number %d has got the semaphore (value = %d)!\n", threadnum, SDL_SemValue(sem));
    22 		SDL_Delay(200);
    23 		SDL_SemPost(sem);
    24 		fprintf(stderr, "Thread number %d has released the semaphore (value = %d)!\n", threadnum, SDL_SemValue(sem));
    25 		SDL_Delay(1); /* For the scheduler */
    26 	}
    27 	printf("Thread number %d exiting.\n", threadnum);
    28 	return 0;
    29 }
    30 
    31 static void killed(int sig)
    32 {
    33 	alive = 0;
    34 }
    35 
    36 static void TestWaitTimeout(void)
    37 {
    38 	Uint32 start_ticks;
    39 	Uint32 end_ticks;
    40 	Uint32 duration;
    41 
    42 	sem = SDL_CreateSemaphore(0);
    43 	printf("Waiting 2 seconds on semaphore\n");
    44 
    45 	start_ticks = SDL_GetTicks();
    46 	SDL_SemWaitTimeout(sem, 2000);
    47 	end_ticks = SDL_GetTicks();
    48 
    49 	duration = end_ticks - start_ticks;
    50 	
    51 	/* Accept a little offset in the effective wait */
    52 	if (duration > 1900 && duration < 2050)
    53 		printf("Wait done.\n");
    54 	else
    55 		fprintf(stderr, "Wait took %d milliseconds\n", duration);
    56 }
    57 
    58 int main(int argc, char **argv)
    59 {
    60 	SDL_Thread *threads[NUM_THREADS];
    61 	uintptr_t i;
    62 	int init_sem;
    63 
    64 	if(argc < 2) {
    65 		fprintf(stderr,"Usage: %s init_value\n", argv[0]);
    66 		return(1);
    67 	}
    68 
    69 	/* Load the SDL library */
    70 	if ( SDL_Init(0) < 0 ) {
    71 		fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
    72 		return(1);
    73 	}
    74 	signal(SIGTERM, killed);
    75 	signal(SIGINT, killed);
    76 	
    77 	init_sem = atoi(argv[1]);
    78 	sem = SDL_CreateSemaphore(init_sem);
    79 	
    80 	printf("Running %d threads, semaphore value = %d\n", NUM_THREADS, init_sem);
    81 	/* Create all the threads */
    82 	for( i = 0; i < NUM_THREADS; ++i ) {
    83 		threads[i] = SDL_CreateThread(ThreadFunc, (void*)i);
    84 	}
    85 
    86 	/* Wait 10 seconds */
    87 	SDL_Delay(10 * 1000);
    88 
    89 	/* Wait for all threads to finish */
    90 	printf("Waiting for threads to finish\n");
    91 	alive = 0;
    92 	for( i = 0; i < NUM_THREADS; ++i ) {
    93 		SDL_WaitThread(threads[i], NULL);
    94 	}
    95 	printf("Finished waiting for threads\n");
    96 
    97 	SDL_DestroySemaphore(sem);
    98 
    99 	TestWaitTimeout();
   100 
   101 	SDL_Quit();
   102 	return(0);
   103 }