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 = std::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 in_port_t lock_client::last_port = 0;
  24
  25 lock_state & lock_client::get_lock_state(lock_protocol::lockid_t lid) {
  26     lock sl(lock_table_lock);
  27     return lock_table[lid]; // creates the lock if it doesn't already exist
  28 }
  29
  30 lock_client::lock_client(string xdst, lock_release_user *_lu) : lu(_lu), next_xid(0) {
  31     cl = unique_ptr<rpcc>(new rpcc(xdst));
  32     if (cl->bind() < 0)
  33         LOG << "lock_client: call bind";
  34
  35     srandom((uint32_t)time(NULL)^last_port);
  36     rlock_port = ((random()%32000) | (0x1 << 10));
  37     id = "127.0.0.1:" + std::to_string(rlock_port);
  38     last_port = rlock_port;
  39     rlsrpc = unique_ptr<rpcs>(new rpcs(rlock_port));
  40     rlsrpc->reg(rlock_protocol::revoke, &lock_client::revoke_handler, this);
  41     rlsrpc->reg(rlock_protocol::retry, &lock_client::retry_handler, this);
  42     rsmc = unique_ptr<rsm_client>(new rsm_client(xdst));
  43     releaser_thread = thread(&lock_client::releaser, this);
  44     rlsrpc->start();
  45 }
  46
  47 lock_client::~lock_client() {
  48     release_fifo.enq(nothing<lock_protocol::lockid_t>());
  49     releaser_thread.join();
  50 }
  51
  52 void lock_client::releaser() {
  53     while (1) {
  54         maybe<lock_protocol::lockid_t> mlid;
  55         release_fifo.deq(&mlid);
  56
  57         if (!mlid) {
  58             LOG << "Releaser stopping";
  59             break;
  60         }
  61
  62         lock_protocol::lockid_t lid = mlid;
  63         LOG << "Releaser: " << lid;
  64
  65         lock_state & st = get_lock_state(lid);
  66         lock sl(st.m);
  67         VERIFY(st.state == lock_state::locked && st.held_by == releaser_thread.get_id());
  68         st.state = lock_state::releasing;
  69         {
  70             sl.unlock();
  71             int r;
  72             rsmc->call(lock_protocol::release, r, lid, id, st.xid);
  73             if (lu)
  74                 lu->dorelease(lid);
  75             sl.lock();
  76         }
  77         st.state = lock_state::none;
  78         LOG << "Lock " << lid << ": none";
  79         st.signal();
  80     }
  81 }
  82
  83 int lock_client::stat(lock_protocol::lockid_t lid) {
  84     VERIFY(0);
  85     int r;
  86     auto ret = (lock_protocol::status)cl->call(lock_protocol::stat, r, lid, id);
  87     VERIFY (ret == lock_protocol::OK);
  88     return r;
  89 }
  90
  91 lock_protocol::status lock_client::acquire(lock_protocol::lockid_t lid) {
  92     lock_state & st = get_lock_state(lid);
  93     lock sl(st.m);
  94     auto self = std::this_thread::get_id();
  95
  96     // check for reentrancy
  97     VERIFY(st.state != lock_state::locked || st.held_by != self);
  98     VERIFY(std::find(st.wanted_by.begin(), st.wanted_by.end(), self)
  99             == st.wanted_by.end());
 100
 101     st.wanted_by.push_back(self);
 102
 103     while (1) {
 104         if (st.state != lock_state::free)
 105             LOG << "Lock " << lid << ": not free";
 106
 107         if (st.state == lock_state::none || st.state == lock_state::retrying) {
 108             if (st.state == lock_state::none) {
 109                 lock l(xid_mutex);
 110                 st.xid = next_xid++;
 111             }
 112             st.state = lock_state::acquiring;
 113             LOG << "Lock " << lid << ": acquiring";
 114             lock_protocol::status result;
 115             {
 116                 sl.unlock();
 117                 int r;
 118                 result = (lock_protocol::status)rsmc->call(lock_protocol::acquire, r, lid, id, st.xid);
 119                 sl.lock();
 120             }
 121             LOG << "acquire returned " << result;
 122             if (result == lock_protocol::OK) {
 123                 st.state = lock_state::free;
 124                 LOG << "Lock " << lid << ": free";
 125             }
 126         }
 127
 128         VERIFY(st.wanted_by.size() != 0);
 129         if (st.state == lock_state::free) {
 130             // is it for me?
 131             auto front = st.wanted_by.front();
 132             if (front == releaser_thread.get_id()) {
 133                 st.wanted_by.pop_front();
 134                 st.state = lock_state::locked;
 135                 st.held_by = releaser_thread.get_id();
 136                 LOG << "Queuing " << lid << " for release";
 137                 release_fifo.enq(just(lid));
 138             } else if (front == self) {
 139                 st.wanted_by.pop_front();
 140                 st.state = lock_state::locked;
 141                 st.held_by = self;
 142                 break;
 143             } else {
 144                 st.signal(front);
 145             }
 146         }
 147
 148         LOG << "waiting...";
 149         st.wait(sl);
 150         LOG << "wait ended";
 151     }
 152
 153     LOG << "Lock " << lid << ": locked";
 154     return lock_protocol::OK;
 155 }
 156
 157 lock_protocol::status lock_client::release(lock_protocol::lockid_t lid) {
 158     lock_state & st = get_lock_state(lid);
 159     lock sl(st.m);
 160     auto self = std::this_thread::get_id();
 161     VERIFY(st.state == lock_state::locked && st.held_by == self);
 162     st.state = lock_state::free;
 163     LOG << "Lock " << lid << ": free";
 164     if (st.wanted_by.size()) {
 165         auto front = st.wanted_by.front();
 166         if (front == releaser_thread.get_id()) {
 167             st.state = lock_state::locked;
 168             st.held_by = releaser_thread.get_id();
 169             st.wanted_by.pop_front();
 170             LOG << "Queuing " << lid << " for release";
 171             release_fifo.enq(just(lid));
 172         } else
 173             st.signal(front);
 174     }
 175     LOG << "Finished signaling.";
 176     return lock_protocol::OK;
 177 }
 178
 179 rlock_protocol::status lock_client::revoke_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t xid) {
 180     LOG << "Revoke handler " << lid << " " << xid;
 181     lock_state & st = get_lock_state(lid);
 182     lock sl(st.m);
 183
 184     if (st.state == lock_state::releasing || st.state == lock_state::none)
 185         return rlock_protocol::OK;
 186
 187     if (st.state == lock_state::free &&
 188         (st.wanted_by.size() == 0 || st.wanted_by.front() == releaser_thread.get_id())) {
 189         // gimme
 190         st.state = lock_state::locked;
 191         st.held_by = releaser_thread.get_id();
 192         if (st.wanted_by.size())
 193             st.wanted_by.pop_front();
 194         release_fifo.enq(just(lid));
 195     } else {
 196         // get in line
 197         st.wanted_by.push_back(releaser_thread.get_id());
 198     }
 199     return rlock_protocol::OK;
 200 }
 201
 202 rlock_protocol::status lock_client::retry_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t) {
 203     lock_state & st = get_lock_state(lid);
 204     lock sl(st.m);
 205     VERIFY(st.state == lock_state::acquiring);
 206     st.state = lock_state::retrying;
 207     LOG << "Lock " << lid << ": none";
 208     st.signal(); // only one thread needs to wake up
 209     return rlock_protocol::OK;
 210 }
 211
 212 t4_lock_client *t4_lock_client_new(const char *dst) {
 213     return (t4_lock_client *)new lock_client(dst);
 214 }
 215
 216 void t4_lock_client_delete(t4_lock_client *client) {
 217     delete (lock_client *)client;
 218 }
 219
 220 t4_status t4_lock_client_acquire(t4_lock_client *client, t4_lockid_t lid) {
 221     return ((lock_client *)client)->acquire(lid);
 222 }
 223
 224 t4_status t4_lock_client_release(t4_lock_client *client, t4_lockid_t lid) {
 225     return ((lock_client *)client)->release(lid);
 226 }
 227
 228 t4_status t4_lock_client_stat(t4_lock_client *client, t4_lockid_t lid) {
 229     return ((lock_client *)client)->stat(lid);
 230 }