lock_client.cc

   1 // RPC stubs for clients to talk to lock_server, and cache the locks.
   2
   3 #include "lock_client.h"
   4 #include <arpa/inet.h>
   5
   6 void lock_state::wait(lock & mutex_lock) {
   7     auto self = this_thread::get_id();
   8     c[self].wait(mutex_lock);
   9     c.erase(self);
  10 }
  11
  12 void lock_state::signal() {
  13     // signal anyone
  14     if (c.begin() != c.end())
  15         c.begin()->second.notify_one();
  16 }
  17
  18 void lock_state::signal(thread::id who) {
  19     if (c.count(who))
  20         c[who].notify_one();
  21 }
  22
  23 typedef map<lock_protocol::lockid_t, lock_state> lock_map;
  24
  25 in_port_t lock_client::last_port = 0;
  26
  27 lock_state & lock_client::get_lock_state(lock_protocol::lockid_t lid) {
  28     lock sl(lock_table_lock);
  29     return lock_table[lid]; // creates the lock if it doesn't already exist
  30 }
  31
  32 lock_client::lock_client(string xdst, lock_release_user *_lu) : lu(_lu), next_xid(0) {
  33     cl = unique_ptr<rpcc>(new rpcc(xdst));
  34     if (cl->bind() < 0)
  35         LOG("lock_client: call bind");
  36
  37     srandom((uint32_t)time(NULL)^last_port);
  38     rlock_port = ((random()%32000) | (0x1 << 10));
  39     id = "127.0.0.1:" + to_string(rlock_port);
  40     last_port = rlock_port;
  41     rlsrpc = unique_ptr<rpcs>(new rpcs(rlock_port));
  42     rlsrpc->reg(rlock_protocol::revoke, &lock_client::revoke_handler, this);
  43     rlsrpc->reg(rlock_protocol::retry, &lock_client::retry_handler, this);
  44     rsmc = unique_ptr<rsm_client>(new rsm_client(xdst));
  45     releaser_thread = thread(&lock_client::releaser, this);
  46     rlsrpc->start();
  47 }
  48
  49 void lock_client::releaser() {
  50     while (1) {
  51         lock_protocol::lockid_t lid;
  52         release_fifo.deq(&lid);
  53         LOG("Releaser: " << lid);
  54
  55         lock_state & st = get_lock_state(lid);
  56         lock sl(st.m);
  57         VERIFY(st.state == lock_state::locked && st.held_by == releaser_thread.get_id());
  58         st.state = lock_state::releasing;
  59         {
  60             sl.unlock();
  61             int r;
  62             rsmc->call(lock_protocol::release, r, lid, id, st.xid);
  63             if (lu)
  64                 lu->dorelease(lid);
  65             sl.lock();
  66         }
  67         st.state = lock_state::none;
  68         LOG("Lock " << lid << ": none");
  69         st.signal();
  70     }
  71 }
  72
  73 int lock_client::stat(lock_protocol::lockid_t lid) {
  74     VERIFY(0);
  75     int r;
  76     auto ret = (lock_protocol::status)cl->call(lock_protocol::stat, r, lid, id);
  77     VERIFY (ret == lock_protocol::OK);
  78     return r;
  79 }
  80
  81 lock_protocol::status lock_client::acquire(lock_protocol::lockid_t lid) {
  82     lock_state & st = get_lock_state(lid);
  83     lock sl(st.m);
  84     auto self = this_thread::get_id();
  85
  86     // check for reentrancy
  87     VERIFY(st.state != lock_state::locked || st.held_by != self);
  88     VERIFY(find(st.wanted_by.begin(), st.wanted_by.end(), self) == st.wanted_by.end());
  89
  90     st.wanted_by.push_back(self);
  91
  92     while (1) {
  93         if (st.state != lock_state::free)
  94             LOG("Lock " << lid << ": not free");
  95
  96         if (st.state == lock_state::none || st.state == lock_state::retrying) {
  97             if (st.state == lock_state::none) {
  98                 lock l(xid_mutex);
  99                 st.xid = next_xid++;
 100             }
 101             st.state = lock_state::acquiring;
 102             LOG("Lock " << lid << ": acquiring");
 103             lock_protocol::status result;
 104             {
 105                 sl.unlock();
 106                 int r;
 107                 result = (lock_protocol::status)rsmc->call(lock_protocol::acquire, r, lid, id, st.xid);
 108                 sl.lock();
 109             }
 110             LOG("acquire returned " << result);
 111             if (result == lock_protocol::OK) {
 112                 st.state = lock_state::free;
 113                 LOG("Lock " << lid << ": free");
 114             }
 115         }
 116
 117         VERIFY(st.wanted_by.size() != 0);
 118         if (st.state == lock_state::free) {
 119             // is it for me?
 120             auto front = st.wanted_by.front();
 121             if (front == releaser_thread.get_id()) {
 122                 st.wanted_by.pop_front();
 123                 st.state = lock_state::locked;
 124                 st.held_by = releaser_thread.get_id();
 125                 LOG("Queuing " << lid << " for release");
 126                 release_fifo.enq(lid);
 127             } else if (front == self) {
 128                 st.wanted_by.pop_front();
 129                 st.state = lock_state::locked;
 130                 st.held_by = self;
 131                 break;
 132             } else {
 133                 st.signal(front);
 134             }
 135         }
 136
 137         LOG("waiting...");
 138         st.wait(sl);
 139         LOG("wait ended");
 140     }
 141
 142     LOG("Lock " << lid << ": locked");
 143     return lock_protocol::OK;
 144 }
 145
 146 lock_protocol::status lock_client::release(lock_protocol::lockid_t lid) {
 147     lock_state & st = get_lock_state(lid);
 148     lock sl(st.m);
 149     auto self = this_thread::get_id();
 150     VERIFY(st.state == lock_state::locked && st.held_by == self);
 151     st.state = lock_state::free;
 152     LOG("Lock " << lid << ": free");
 153     if (st.wanted_by.size()) {
 154         auto front = st.wanted_by.front();
 155         if (front == releaser_thread.get_id()) {
 156             st.state = lock_state::locked;
 157             st.held_by = releaser_thread.get_id();
 158             st.wanted_by.pop_front();
 159             LOG("Queuing " << lid << " for release");
 160             release_fifo.enq(lid);
 161         } else
 162             st.signal(front);
 163     }
 164     LOG("Finished signaling.");
 165     return lock_protocol::OK;
 166 }
 167
 168 rlock_protocol::status lock_client::revoke_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t xid) {
 169     LOG("Revoke handler " << lid << " " << xid);
 170     lock_state & st = get_lock_state(lid);
 171     lock sl(st.m);
 172
 173     if (st.state == lock_state::releasing || st.state == lock_state::none)
 174         return rlock_protocol::OK;
 175
 176     if (st.state == lock_state::free &&
 177         (st.wanted_by.size() == 0 || st.wanted_by.front() == releaser_thread.get_id())) {
 178         // gimme
 179         st.state = lock_state::locked;
 180         st.held_by = releaser_thread.get_id();
 181         if (st.wanted_by.size())
 182             st.wanted_by.pop_front();
 183         release_fifo.enq(lid);
 184     } else {
 185         // get in line
 186         st.wanted_by.push_back(releaser_thread.get_id());
 187     }
 188     return rlock_protocol::OK;
 189 }
 190
 191 rlock_protocol::status lock_client::retry_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t) {
 192     lock_state & st = get_lock_state(lid);
 193     lock sl(st.m);
 194     VERIFY(st.state == lock_state::acquiring);
 195     st.state = lock_state::retrying;
 196     LOG("Lock " << lid << ": none");
 197     st.signal(); // only one thread needs to wake up
 198     return rlock_protocol::OK;
 199 }
 200
 201 t4_lock_client *t4_lock_client_new(const char *dst) {
 202     return (t4_lock_client *)new lock_client(dst);
 203 }
 204
 205 void t4_lock_client_delete(t4_lock_client *client) {
 206     delete (lock_client *)client;
 207 }
 208
 209 t4_status t4_lock_client_acquire(t4_lock_client *client, t4_lockid_t lid) {
 210     return ((lock_client *)client)->acquire(lid);
 211 }
 212
 213 t4_status t4_lock_client_release(t4_lock_client *client, t4_lockid_t lid) {
 214     return ((lock_client *)client)->release(lid);
 215 }
 216
 217 t4_status t4_lock_client_stat(t4_lock_client *client, t4_lockid_t lid) {
 218     return ((lock_client *)client)->stat(lid);
 219 }