From f1b088cb8f908e4ea07ec27dc6d43ad9cebc41f4 Mon Sep 17 00:00:00 2001
From: "Bradley C. Kuszmaul" <bradley@tokutek.com>
Date: Mon, 19 Nov 2007 22:01:16 +0000
Subject: [PATCH] Check interprocess pthread rwlocks o see if they work.  Fixes
 #4

git-svn-id: file:///svn/tokudb@671 c7de825b-a66e-492c-adef-691d508d4ae1
---
 newbrt/locking-benchmarks/process_locks.c | 143 ++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 newbrt/locking-benchmarks/process_locks.c

diff --git a/newbrt/locking-benchmarks/process_locks.c b/newbrt/locking-benchmarks/process_locks.c
new file mode 100644
index 00000000000..5c6d831b6d8
--- /dev/null
+++ b/newbrt/locking-benchmarks/process_locks.c
@@ -0,0 +1,143 @@
+/* Test pthread rwlocks in multiprocess environment. */
+
+/* How expensive is
+ *   - Obtaining a read-only lock for the first obtainer.
+ *   - Obtaining it for the second one?
+ *   - The third one? */
+
+#include <assert.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+
+float tdiff (struct timeval *start, struct timeval *end) {
+    return 1e6*(end->tv_sec-start->tv_sec) +(end->tv_usec - start->tv_usec);
+}
+
+#define FILE "process.data"
+
+int main (int argc __attribute__((__unused__)), char *argv[] __attribute__((__unused__))) {
+    int r;
+    int fd;
+    void *p;
+    fd=open(FILE, O_CREAT|O_RDWR|O_TRUNC, 0666); assert(fd>=0);
+    int i;
+    for (i=0; i<4096; i++) {
+	r=write(fd, "\000", 1);
+	assert(r==1);
+    }
+    p=mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+    if (p==MAP_FAILED) {
+	printf("err=%d %s (EPERM=%d)\n", errno, strerror(errno), EPERM);
+    }
+    assert(p!=MAP_FAILED);
+    r=close(fd); assert(r==0);
+
+    pthread_rwlockattr_t attr;
+    pthread_rwlock_t *lock=p;
+    r=pthread_rwlockattr_init(&attr);                               assert(r==0);
+    r=pthread_rwlockattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); assert(r==0);
+    r=pthread_rwlock_init(lock, &attr);                             assert(r==0);
+    r=pthread_rwlock_init(lock+1, &attr);                             assert(r==0);
+
+    r=pthread_rwlock_wrlock(lock);
+
+    pid_t pid;
+    if ((pid=fork())==0) {
+	// I'm the child
+	r = munmap(p, 4096); assert(r==0);
+	fd = open(FILE, O_RDWR, 0666); assert(fd>=0);
+	p=mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+	assert(p!=MAP_FAILED);
+	r=close(fd); assert(r==0);
+	
+	printf("A0\n");
+	r=pthread_rwlock_wrlock(lock);
+	printf("C\n");
+	sleep(1);
+    
+	r=pthread_rwlock_unlock(lock);
+	printf("D\n");
+
+	r=pthread_rwlock_rdlock(lock);
+	printf("E0\n");
+	sleep(1);
+
+    } else {
+	printf("A1\n");
+	sleep(1);
+	printf("B\n");
+	r=pthread_rwlock_unlock(lock); // release the lock grabbed before the fork
+	assert(r==0);
+
+	sleep(1);
+	r=pthread_rwlock_rdlock(lock);
+	assert(r==0);
+	printf("E1\n");
+	sleep(1);
+
+	int status;
+	pid_t waited=wait(&status);
+	assert(waited==pid);
+    }
+    return 0;    
+    
+    
+#if 0    
+
+    int j;
+    int i;
+    int r;
+    struct timeval start, end;
+    for (j=0; j<3; j++) {
+	for (i=0; i<K; i++) {
+	    r=pthread_rwlock_init(&rwlocks[i], NULL);
+	    assert(r==0);
+	}
+	gettimeofday(&start, 0);
+	for (i=0; i<K; i++) {
+	    r = pthread_rwlock_tryrdlock(&rwlocks[i]);
+	    assert(r==0);
+	}
+	gettimeofday(&end, 0);
+	printf("pthread_rwlock_tryrdlock took %9.3fus for %d ops:  %9.3fus/lock (%9.3fMops/s)\n", tdiff(&start,&end), K, tdiff(&start,&end)/K, K/tdiff(&start,&end));
+    }
+
+    for (j=0; j<3; j++) {
+	for (i=0; i<K; i++) {
+	    r=pthread_rwlock_init(&rwlocks[i], NULL);
+	    assert(r==0);
+	}
+	gettimeofday(&start, 0);
+	for (i=0; i<K; i++) {
+	    r = pthread_rwlock_rdlock(&rwlocks[i]);
+	    assert(r==0);
+	}
+	gettimeofday(&end, 0);
+	printf("pthread_rwlock_rdlock    took %9.3fus for %d ops:  %9.3fus/lock (%9.3fMops/s)\n", tdiff(&start,&end), K, tdiff(&start,&end)/K, K/tdiff(&start,&end));
+    }
+
+    for (j=0; j<3; j++) {
+	for (i=0; i<K; i++) {
+	    blocks[i].state=0;
+	    blocks[i].mutex=0;
+	}
+	gettimeofday(&start, 0);
+	for (i=0; i<K; i++) {
+	    brwl_rlock(&blocks[i]);
+	}
+	gettimeofday(&end, 0);
+	printf("brwl_rlock               took %9.3fus for %d ops:  %9.3fus/lock (%9.3fMops/s)\n", tdiff(&start,&end), K, tdiff(&start,&end)/K, K/tdiff(&start,&end));
+    }
+    return 0;
+#endif
+}