-
Notifications
You must be signed in to change notification settings - Fork 0
/
lock_server.cc
97 lines (78 loc) · 2.12 KB
/
lock_server.cc
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
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
// the lock server implementation
#include "lock_server.h"
#include <sstream>
#include <stdio.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <map>
#include <pthread.h>
using namespace std;
// with the use of semaphores, this could be extended to have locks for read and write.
lock_server::lock_server():
nacquire (0)
{
// here is our pthreads mutex
pthread_mutex_init(&mu,NULL);
pthread_cond_init(&condition,NULL);
// cout << "lock server constructed";
}
lock_protocol::status
lock_server::stat(int clt, lock_protocol::lockid_t lid, int &r)
{
lock_protocol::status ret = lock_protocol::OK;
printf("stat request from clt %d\n", clt);
r = nacquire;
return ret;
}
lock_protocol::status
lock_server::acquire(lock_protocol::lockid_t lid, int &r)
{
//cout << "attempting to acquire " << lid;
//locks the semaphores;
// cout << " waiting for lock...";
pthread_mutex_lock(&mu);
// means we need to add id to the map
if(semaphores.find(lid)==semaphores.end() )
{
//cout << "adding new mutex to list";
lock_info * t = new lock_info;
t->lock = 1;
pthread_cond_init(&(t->condition),NULL);
semaphores[lid] = *t;
//unlock since we are done with semaphores
pthread_mutex_unlock(&mu);
return lock_protocol::OK;
}
//unlocks the semaphores;
// pthread_mutex_unlock(&mu);
// cout << "entering blocking";
// blocking loop
while(1)
{
//pthread_mutex_lock(&mu);
if(semaphores[lid].lock == 0)
break;
//cout << "waiting on condition for " << lid;
pthread_cond_wait(&(semaphores[lid].condition),&mu);
//cout << "woke up";
//pthread_mutex_unlock(&mu);
}
//here we have mu lock and can aqcuire semaphore lid
semaphores[lid].lock = 1;
nacquire++;
pthread_mutex_unlock(&mu);
//cout << "\nacquired";
return lock_protocol::OK;
}
lock_protocol::status
lock_server::release(lock_protocol::lockid_t lid, int &r)
{
pthread_mutex_lock(&mu);
semaphores[lid].lock = 0;
nacquire--;
//pthread_mutex_unlock(&mu);
// cout << "\nsignal for "<< lid;
pthread_cond_signal(&(semaphores[lid].condition));
pthread_mutex_unlock(&mu);
return lock_protocol::OK;
}