73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
// author: Marc Orr
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#include <pthread.h>
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#include <stdio.h>
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#include <stdlib.h>
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#define NUM_TRIES 1000
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// Make sure that flags and wait sit in different cache lines
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volatile int flags[10];
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volatile int wait[10];
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pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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void *DoWork1(void *threadid)
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{
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flags[0] = flags[0] + 1;
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wait[0] = 0;
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pthread_exit(0);
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}
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void *DoWork2(void *threadid)
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{
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pthread_mutex_lock (&mutex);
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flags[0] = flags[0] + 1;
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pthread_mutex_unlock (&mutex);
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pthread_exit(0);
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}
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////////////////////////////////////////////////////////////////////////////////
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// Program main
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////////////////////////////////////////////////////////////////////////////////
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int main( int argc, char** argv)
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{
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// stuff for thread
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pthread_t threads[1];
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// initialize global variables
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flags[0] = 0;
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wait[0] = 1;
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// monitor (via gcc intrinsic)
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__builtin_ia32_monitor ((void *)&flags, 0, 0);
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// invalidate flags in this cpu's cache
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pthread_create(&threads[0], NULL, DoWork1, NULL);
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while (wait[0]);
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// launch thread to invalidate address being monitored
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pthread_create(&threads[0], NULL, DoWork2, NULL);
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// wait for other thread to modify flags
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int mwait_cnt = 0;
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do {
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pthread_mutex_lock (&mutex);
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if (flags[0] != 2) {
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pthread_mutex_unlock (&mutex);
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__builtin_ia32_mwait(0, 0);
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} else {
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pthread_mutex_unlock (&mutex);
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}
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mwait_cnt++;
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} while (flags[0] != 2 && mwait_cnt < NUM_TRIES);
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// test may hang if mwait is not working
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if (flags[0]==2) {
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printf("mwait regression PASSED, flags[0] = %d\n", flags[0]);
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} else {
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printf("mwait regression FAILED, flags[0] = %d\n", flags[0]);
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}
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return 0;
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}
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