lock_client.cc

   1 // RPC stubs for clients to talk to lock_server, and cache the locks.
   2
   3 #include "include/lock_client.h"
   4 #include <arpa/inet.h>
   5
   6 void lock_client::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_client::lock_state::signal() {
  13     // signal anyone
  14     if (c.begin() != c.end())
  15         c.begin()->second.notify_one();
  16 }
  17
  18 void lock_client::lock_state::signal(thread::id who) {
  19     if (c.count(who))
  20         c[who].notify_one();
  21 }
  22
  23 lock_client::lock_state & lock_client::get_lock_state(lock_protocol::lockid_t lid) {
  24     lock sl(lock_table_lock);
  25     return lock_table[lid]; // creates the lock if it doesn't already exist
  26 }
  27
  28 lock_client::lock_client(string xdst) {
  29     rlock_port = std::uniform_int_distribution<in_port_t>(1024,32000+1024)(global->random_generator);
  30     id = "127.0.0.1:" + std::to_string(rlock_port);
  31     rlsrpc = std::make_unique<rpcs>(rlock_port);
  32     rlsrpc->reg(rlock_protocol::revoke, &lock_client::revoke_handler, this);
  33     rlsrpc->reg(rlock_protocol::retry, &lock_client::retry_handler, this);
  34     rsmc = std::make_unique<rsm_client>(xdst);
  35     releaser_thread = thread(&lock_client::releaser, this);
  36     rlsrpc->start();
  37 }
  38
  39 lock_client::~lock_client() {
  40     release_fifo.enq(nothing<lock_protocol::lockid_t>());
  41     releaser_thread.join();
  42 }
  43
  44 void lock_client::releaser() {
  45     while (auto mlid = release_fifo.deq()) {
  46         lock_protocol::lockid_t lid = mlid;
  47         LOG << "Releaser: " << lid;
  48
  49         lock_state & st = get_lock_state(lid);
  50         lock sl(st.m);
  51         VERIFY(st.state == lock_state::locked && st.held_by == releaser_thread.get_id());
  52         st.state = lock_state::releasing;
  53         {
  54             sl.unlock();
  55             int r;
  56             rsmc->call(lock_protocol::release, r, lid, id, st.xid);
  57             sl.lock();
  58         }
  59         st.state = lock_state::none;
  60         LOG << "Lock " << lid << ": none";
  61         st.signal();
  62     }
  63     LOG << "Releaser stopping";
  64 }
  65
  66 lock_protocol::status lock_client::acquire(lock_protocol::lockid_t lid) {
  67     lock_state & st = get_lock_state(lid);
  68     lock sl(st.m);
  69     auto self = std::this_thread::get_id();
  70
  71     // check for reentrancy
  72     VERIFY(st.state != lock_state::locked || st.held_by != self);
  73     VERIFY(std::find(st.wanted_by.begin(), st.wanted_by.end(), self)
  74             == st.wanted_by.end());
  75
  76     st.wanted_by.push_back(self);
  77
  78     while (1) {
  79         if (st.state != lock_state::free)
  80             LOG << "Lock " << lid << ": not free";
  81
  82         if (st.state == lock_state::none || st.state == lock_state::retrying) {
  83             if (st.state == lock_state::none) {
  84                 lock l(xid_mutex);
  85                 st.xid = next_xid++;
  86             }
  87             st.state = lock_state::acquiring;
  88             LOG << "Lock " << lid << ": acquiring";
  89             lock_protocol::status result;
  90             {
  91                 sl.unlock();
  92                 int r;
  93                 result = (lock_protocol::status)rsmc->call(lock_protocol::acquire, r, lid, id, st.xid);
  94                 sl.lock();
  95             }
  96             LOG << "acquire returned " << result;
  97             if (result == lock_protocol::OK) {
  98                 st.state = lock_state::free;
  99                 LOG << "Lock " << lid << ": free";
 100             }
 101         }
 102
 103         VERIFY(st.wanted_by.size() != 0);
 104         if (st.state == lock_state::free) {
 105             // is it for me?
 106             auto front = st.wanted_by.front();
 107             if (front == releaser_thread.get_id()) {
 108                 st.wanted_by.pop_front();
 109                 st.state = lock_state::locked;
 110                 st.held_by = releaser_thread.get_id();
 111                 LOG << "Queuing " << lid << " for release";
 112                 release_fifo.enq(just(lid));
 113             } else if (front == self) {
 114                 st.wanted_by.pop_front();
 115                 st.state = lock_state::locked;
 116                 st.held_by = self;
 117                 break;
 118             } else {
 119                 st.signal(front);
 120             }
 121         }
 122
 123         LOG << "waiting...";
 124         st.wait(sl);
 125         LOG << "wait ended";
 126     }
 127
 128     LOG << "Lock " << lid << ": locked";
 129     return lock_protocol::OK;
 130 }
 131
 132 lock_protocol::status lock_client::release(lock_protocol::lockid_t lid) {
 133     lock_state & st = get_lock_state(lid);
 134     lock sl(st.m);
 135     auto self = std::this_thread::get_id();
 136     VERIFY(st.state == lock_state::locked && st.held_by == self);
 137     st.state = lock_state::free;
 138     LOG << "Lock " << lid << ": free";
 139     if (st.wanted_by.size()) {
 140         auto front = st.wanted_by.front();
 141         if (front == releaser_thread.get_id()) {
 142             st.state = lock_state::locked;
 143             st.held_by = releaser_thread.get_id();
 144             st.wanted_by.pop_front();
 145             LOG << "Queuing " << lid << " for release";
 146             release_fifo.enq(just(lid));
 147         } else
 148             st.signal(front);
 149     }
 150     LOG << "Finished signaling.";
 151     return lock_protocol::OK;
 152 }
 153
 154 rlock_protocol::status lock_client::revoke_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t xid) {
 155     LOG << "Revoke handler " << lid << " " << xid;
 156     lock_state & st = get_lock_state(lid);
 157     lock sl(st.m);
 158
 159     if (st.state == lock_state::releasing || st.state == lock_state::none)
 160         return rlock_protocol::OK;
 161
 162     if (st.state == lock_state::free &&
 163         (st.wanted_by.size() == 0 || st.wanted_by.front() == releaser_thread.get_id())) {
 164         // gimme
 165         st.state = lock_state::locked;
 166         st.held_by = releaser_thread.get_id();
 167         if (st.wanted_by.size())
 168             st.wanted_by.pop_front();
 169         release_fifo.enq(just(lid));
 170     } else {
 171         // get in line
 172         st.wanted_by.push_back(releaser_thread.get_id());
 173     }
 174     return rlock_protocol::OK;
 175 }
 176
 177 rlock_protocol::status lock_client::retry_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t) {
 178     lock_state & st = get_lock_state(lid);
 179     lock sl(st.m);
 180     VERIFY(st.state == lock_state::acquiring);
 181     st.state = lock_state::retrying;
 182     LOG << "Lock " << lid << ": none";
 183     st.signal(); // only one thread needs to wake up
 184     return rlock_protocol::OK;
 185 }
 186
 187 t4_lock_client *t4_lock_client_new(const char *dst) {
 188     return (t4_lock_client *)new lock_client(dst);
 189 }
 190
 191 void t4_lock_client_delete(t4_lock_client *client) {
 192     delete (lock_client *)client;
 193 }
 194
 195 t4_status t4_lock_client_acquire(t4_lock_client *client, t4_lockid_t lid) {
 196     return ((lock_client *)client)->acquire(lid);
 197 }
 198
 199 t4_status t4_lock_client_release(t4_lock_client *client, t4_lockid_t lid) {
 200     return ((lock_client *)client)->release(lid);
 201 }