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 = 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     rpcs *rlsrpc = 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 = new rsm_client(xdst);
  45     releaser_thread = thread(&lock_client::releaser, this);
  46 }
  47
  48 void lock_client::releaser() [[noreturn]] {
  49     while (1) {
  50         lock_protocol::lockid_t lid;
  51         release_fifo.deq(&lid);
  52         LOG("Releaser: " << lid);
  53
  54         lock_state &st = get_lock_state(lid);
  55         lock sl(st.m);
  56         VERIFY(st.state == lock_state::locked && st.held_by == releaser_thread.get_id());
  57         st.state = lock_state::releasing;
  58         {
  59             sl.unlock();
  60             int r;
  61             rsmc->call(lock_protocol::release, r, lid, id, st.xid);
  62             if (lu)
  63                 lu->dorelease(lid);
  64             sl.lock();
  65         }
  66         st.state = lock_state::none;
  67         LOG("Lock " << lid << ": none");
  68         st.signal();
  69     }
  70 }
  71
  72 int lock_client::stat(lock_protocol::lockid_t lid) {
  73     VERIFY(0);
  74     int r;
  75     auto ret = (lock_protocol::status)cl->call(lock_protocol::stat, r, cl->id(), lid);
  76     VERIFY (ret == lock_protocol::OK);
  77     return r;
  78 }
  79
  80 lock_protocol::status lock_client::acquire(lock_protocol::lockid_t lid) {
  81     lock_state &st = get_lock_state(lid);
  82     lock sl(st.m);
  83     auto self = this_thread::get_id();
  84
  85     // check for reentrancy
  86     VERIFY(st.state != lock_state::locked || st.held_by != self);
  87     VERIFY(find(st.wanted_by.begin(), st.wanted_by.end(), self) == st.wanted_by.end());
  88
  89     st.wanted_by.push_back(self);
  90
  91     while (1) {
  92         if (st.state != lock_state::free)
  93             LOG("Lock " << lid << ": not free");
  94
  95         if (st.state == lock_state::none || st.state == lock_state::retrying) {
  96             if (st.state == lock_state::none) {
  97                 lock l(xid_mutex);
  98                 st.xid = next_xid++;
  99             }
 100             st.state = lock_state::acquiring;
 101             LOG("Lock " << lid << ": acquiring");
 102             lock_protocol::status result;
 103             {
 104                 sl.unlock();
 105                 int r;
 106                 result = (lock_protocol::status)rsmc->call(lock_protocol::acquire, r, lid, id, st.xid);
 107                 sl.lock();
 108             }
 109             LOG("acquire returned " << result);
 110             if (result == lock_protocol::OK) {
 111                 st.state = lock_state::free;
 112                 LOG("Lock " << lid << ": free");
 113             }
 114         }
 115
 116         VERIFY(st.wanted_by.size() != 0);
 117         if (st.state == lock_state::free) {
 118             // is it for me?
 119             auto front = st.wanted_by.front();
 120             if (front == releaser_thread.get_id()) {
 121                 st.wanted_by.pop_front();
 122                 st.state = lock_state::locked;
 123                 st.held_by = releaser_thread.get_id();
 124                 LOG("Queuing " << lid << " for release");
 125                 release_fifo.enq(lid);
 126             } else if (front == self) {
 127                 st.wanted_by.pop_front();
 128                 st.state = lock_state::locked;
 129                 st.held_by = self;
 130                 break;
 131             } else {
 132                 st.signal(front);
 133             }
 134         }
 135
 136         LOG("waiting...");
 137         st.wait(sl);
 138         LOG("wait ended");
 139     }
 140
 141     LOG("Lock " << lid << ": locked");
 142     return lock_protocol::OK;
 143 }
 144
 145 lock_protocol::status lock_client::release(lock_protocol::lockid_t lid) {
 146     lock_state &st = get_lock_state(lid);
 147     lock sl(st.m);
 148     auto self = this_thread::get_id();
 149     VERIFY(st.state == lock_state::locked && st.held_by == self);
 150     st.state = lock_state::free;
 151     LOG("Lock " << lid << ": free");
 152     if (st.wanted_by.size()) {
 153         auto front = st.wanted_by.front();
 154         if (front == releaser_thread.get_id()) {
 155             st.state = lock_state::locked;
 156             st.held_by = releaser_thread.get_id();
 157             st.wanted_by.pop_front();
 158             LOG("Queuing " << lid << " for release");
 159             release_fifo.enq(lid);
 160         } else
 161             st.signal(front);
 162     }
 163     LOG("Finished signaling.");
 164     return lock_protocol::OK;
 165 }
 166
 167 rlock_protocol::status lock_client::revoke_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t xid) {
 168     LOG("Revoke handler " << lid << " " << xid);
 169     lock_state &st = get_lock_state(lid);
 170     lock sl(st.m);
 171
 172     if (st.state == lock_state::releasing || st.state == lock_state::none)
 173         return rlock_protocol::OK;
 174
 175     if (st.state == lock_state::free &&
 176         (st.wanted_by.size() == 0 || st.wanted_by.front() == releaser_thread.get_id())) {
 177         // gimme
 178         st.state = lock_state::locked;
 179         st.held_by = releaser_thread.get_id();
 180         if (st.wanted_by.size())
 181             st.wanted_by.pop_front();
 182         release_fifo.enq(lid);
 183     } else {
 184         // get in line
 185         st.wanted_by.push_back(releaser_thread.get_id());
 186     }
 187     return rlock_protocol::OK;
 188 }
 189
 190 rlock_protocol::status lock_client::retry_handler(int &, lock_protocol::lockid_t lid, lock_protocol::xid_t) {
 191     lock_state &st = get_lock_state(lid);
 192     lock sl(st.m);
 193     VERIFY(st.state == lock_state::acquiring);
 194     st.state = lock_state::retrying;
 195     LOG("Lock " << lid << ": none");
 196     st.signal(); // only one thread needs to wake up
 197     return rlock_protocol::OK;
 198 }
 199
 200 t4_lock_client *t4_lock_client_new(const char *dst) {
 201     return (t4_lock_client *)new lock_client(dst);
 202 }
 203
 204 void t4_lock_client_delete(t4_lock_client *client) {
 205     delete (lock_client *)client;
 206 }
 207
 208 t4_status t4_lock_client_acquire(t4_lock_client *client, t4_lockid_t lid) {
 209     return ((lock_client *)client)->acquire(lid);
 210 }
 211
 212 t4_status t4_lock_client_release(t4_lock_client *client, t4_lockid_t lid) {
 213     return ((lock_client *)client)->release(lid);
 214 }
 215
 216 t4_status t4_lock_client_stat(t4_lock_client *client, t4_lockid_t lid) {
 217     return ((lock_client *)client)->stat(lid);
 218 }