src/event.cc

   1 /*
   2  * Copyright (C) 1996-2015 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 /* DEBUG: section 41    Event Processing */
  10
  11 #include "squid.h"
  12 #include "compat/drand48.h"
  13 #include "event.h"
  14 #include "mgr/Registration.h"
  15 #include "profiler/Profiler.h"
  16 #include "SquidTime.h"
  17 #include "Store.h"
  18 #include "tools.h"
  19
  20 #include <cmath>
  21
  22 /* The list of event processes */
  23
  24 static OBJH eventDump;
  25 static const char *last_event_ran = NULL;
  26
  27 // This AsyncCall dialer can be configured to check that the event cbdata is
  28 // valid before calling the event handler
  29 class EventDialer: public CallDialer
  30 {
  31 public:
  32     typedef CallDialer Parent;
  33
  34     EventDialer(EVH *aHandler, void *anArg, bool lockedArg);
  35     EventDialer(const EventDialer &d);
  36     virtual ~EventDialer();
  37
  38     virtual void print(std::ostream &os) const;
  39     virtual bool canDial(AsyncCall &call);
  40
  41     void dial(AsyncCall &) { theHandler(theArg); }
  42
  43 private:
  44     EVH *theHandler;
  45     void *theArg;
  46     bool isLockedArg;
  47 };
  48
  49 EventDialer::EventDialer(EVH *aHandler, void *anArg, bool lockedArg):
  50     theHandler(aHandler), theArg(anArg), isLockedArg(lockedArg)
  51 {
  52     if (isLockedArg)
  53         (void)cbdataReference(theArg);
  54 }
  55
  56 EventDialer::EventDialer(const EventDialer &d):
  57     theHandler(d.theHandler), theArg(d.theArg), isLockedArg(d.isLockedArg)
  58 {
  59     if (isLockedArg)
  60         (void)cbdataReference(theArg);
  61 }
  62
  63 EventDialer::~EventDialer()
  64 {
  65     if (isLockedArg)
  66         cbdataReferenceDone(theArg);
  67 }
  68
  69 bool
  70 EventDialer::canDial(AsyncCall &call)
  71 {
  72     // TODO: add Parent::canDial() that always returns true
  73     //if (!Parent::canDial())
  74     //    return false;
  75
  76     if (isLockedArg && !cbdataReferenceValid(theArg))
  77         return call.cancel("stale handler data");
  78
  79     return true;
  80 }
  81
  82 void
  83 EventDialer::print(std::ostream &os) const
  84 {
  85     os << '(';
  86     if (theArg)
  87         os << theArg << (isLockedArg ? "*?" : "");
  88     os << ')';
  89 }
  90
  91 ev_entry::ev_entry(char const * aName, EVH * aFunction, void * aArgument, double evWhen,
  92                    int aWeight, bool haveArgument) : name(aName), func(aFunction),
  93     arg(haveArgument ? cbdataReference(aArgument) : aArgument), when(evWhen), weight(aWeight),
  94     cbdata(haveArgument)
  95 {
  96 }
  97
  98 ev_entry::~ev_entry()
  99 {
 100     if (cbdata)
 101         cbdataReferenceDone(arg);
 102 }
 103
 104 void
 105 eventAdd(const char *name, EVH * func, void *arg, double when, int weight, bool cbdata)
 106 {
 107     EventScheduler::GetInstance()->schedule(name, func, arg, when, weight, cbdata);
 108 }
 109
 110 /* same as eventAdd but adds a random offset within +-1/3 of delta_ish */
 111 void
 112 eventAddIsh(const char *name, EVH * func, void *arg, double delta_ish, int weight)
 113 {
 114     if (delta_ish >= 3.0) {
 115         const double two_third = (2.0 * delta_ish) / 3.0;
 116         delta_ish = two_third + (drand48() * two_third);
 117         /*
 118          * I'm sure drand48() isn't portable.  Tell me what function
 119          * you have that returns a random double value in the range 0,1.
 120          */
 121     }
 122
 123     eventAdd(name, func, arg, delta_ish, weight);
 124 }
 125
 126 void
 127 eventDelete(EVH * func, void *arg)
 128 {
 129     EventScheduler::GetInstance()->cancel(func, arg);
 130 }
 131
 132 void
 133 eventInit(void)
 134 {
 135     Mgr::RegisterAction("events", "Event Queue", eventDump, 0, 1);
 136 }
 137
 138 static void
 139 eventDump(StoreEntry * sentry)
 140 {
 141     EventScheduler::GetInstance()->dump(sentry);
 142 }
 143
 144 void
 145 eventFreeMemory(void)
 146 {
 147     EventScheduler::GetInstance()->clean();
 148 }
 149
 150 int
 151 eventFind(EVH * func, void *arg)
 152 {
 153     return EventScheduler::GetInstance()->find(func, arg);
 154 }
 155
 156 EventScheduler EventScheduler::_instance;
 157
 158 EventScheduler::EventScheduler(): tasks(NULL)
 159 {}
 160
 161 EventScheduler::~EventScheduler()
 162 {
 163     clean();
 164 }
 165
 166 void
 167 EventScheduler::cancel(EVH * func, void *arg)
 168 {
 169     ev_entry **E;
 170     ev_entry *event;
 171
 172     for (E = &tasks; (event = *E) != NULL; E = &(*E)->next) {
 173         if (event->func != func)
 174             continue;
 175
 176         if (arg && event->arg != arg)
 177             continue;
 178
 179         *E = event->next;
 180
 181         delete event;
 182
 183         if (arg)
 184             return;
 185         /*
 186          * DPW 2007-04-12
 187          * Since this method may now delete multiple events (when
 188          * arg is NULL) it no longer returns after a deletion and
 189          * we have a potential NULL pointer problem.  If we just
 190          * deleted the last event in the list then *E is now equal
 191          * to NULL.  We need to break here or else we'll get a NULL
 192          * pointer dereference in the last clause of the for loop.
 193          */
 194         if (NULL == *E)
 195             break;
 196     }
 197
 198     if (arg)
 199         debug_trap("eventDelete: event not found");
 200 }
 201
 202 // The event API does not guarantee exact timing, but guarantees that no event
 203 // is fired before it is due. We may delay firing, but never fire too early.
 204 int
 205 EventScheduler::timeRemaining() const
 206 {
 207     if (!tasks)
 208         return EVENT_IDLE;
 209
 210     if (tasks->when <= current_dtime) // we are on time or late
 211         return 0; // fire the event ASAP
 212
 213     const double diff = tasks->when - current_dtime; // microseconds
 214     // Round UP: If we come back a nanosecond earlier, we will wait again!
 215     const int timeLeft = static_cast<int>(ceil(1000*diff)); // milliseconds
 216     // Avoid hot idle: A series of rapid select() calls with zero timeout.
 217     const int minDelay = 1; // millisecond
 218     return max(minDelay, timeLeft);
 219 }
 220
 221 int
 222 EventScheduler::checkEvents(int)
 223 {
 224     int result = timeRemaining();
 225     if (result != 0)
 226         return result;
 227
 228     PROF_start(eventRun);
 229
 230     do {
 231         ev_entry *event = tasks;
 232         assert(event);
 233
 234         /* XXX assumes event->name is static memory! */
 235         AsyncCall::Pointer call = asyncCall(41,5, event->name,
 236                                             EventDialer(event->func, event->arg, event->cbdata));
 237         ScheduleCallHere(call);
 238
 239         last_event_ran = event->name; // XXX: move this to AsyncCallQueue
 240         const bool heavy = event->weight &&
 241                            (!event->cbdata || cbdataReferenceValid(event->arg));
 242
 243         tasks = event->next;
 244         delete event;
 245
 246         result = timeRemaining();
 247
 248         // XXX: We may be called again during the same event loop iteration.
 249         // Is there a point in breaking now?
 250         if (heavy)
 251             break; // do not dequeue events following a heavy event
 252     } while (result == 0);
 253
 254     PROF_stop(eventRun);
 255     return result;
 256 }
 257
 258 void
 259 EventScheduler::clean()
 260 {
 261     while (ev_entry * event = tasks) {
 262         tasks = event->next;
 263         delete event;
 264     }
 265
 266     tasks = NULL;
 267 }
 268
 269 void
 270 EventScheduler::dump(StoreEntry * sentry)
 271 {
 272
 273     ev_entry *e = tasks;
 274
 275     if (last_event_ran)
 276         storeAppendPrintf(sentry, "Last event to run: %s\n\n", last_event_ran);
 277
 278     storeAppendPrintf(sentry, "%-25s\t%-15s\t%s\t%s\n",
 279                       "Operation",
 280                       "Next Execution",
 281                       "Weight",
 282                       "Callback Valid?");
 283
 284     while (e != NULL) {
 285         storeAppendPrintf(sentry, "%-25s\t%0.3f sec\t%5d\t %s\n",
 286                           e->name, e->when ? e->when - current_dtime : 0, e->weight,
 287                           (e->arg && e->cbdata) ? cbdataReferenceValid(e->arg) ? "yes" : "no" : "N/A");
 288         e = e->next;
 289     }
 290 }
 291
 292 bool
 293 EventScheduler::find(EVH * func, void * arg)
 294 {
 295
 296     ev_entry *event;
 297
 298     for (event = tasks; event != NULL; event = event->next) {
 299         if (event->func == func && event->arg == arg)
 300             return true;
 301     }
 302
 303     return false;
 304 }
 305
 306 EventScheduler *
 307 EventScheduler::GetInstance()
 308 {
 309     return &_instance;
 310 }
 311
 312 void
 313 EventScheduler::schedule(const char *name, EVH * func, void *arg, double when, int weight, bool cbdata)
 314 {
 315     // Use zero timestamp for when=0 events: Many of them are async calls that
 316     // must fire in the submission order. We cannot use current_dtime for them
 317     // because it may decrease if system clock is adjusted backwards.
 318     const double timestamp = when > 0.0 ? current_dtime + when : 0;
 319     ev_entry *event = new ev_entry(name, func, arg, timestamp, weight, cbdata);
 320
 321     ev_entry **E;
 322     debugs(41, 7, HERE << "schedule: Adding '" << name << "', in " << when << " seconds");
 323     /* Insert after the last event with the same or earlier time */
 324
 325     for (E = &tasks; *E; E = &(*E)->next) {
 326         if ((*E)->when > event->when)
 327             break;
 328     }
 329
 330     event->next = *E;
 331     *E = event;
 332 }
 333