src/base/JobWait.cc

   1 /*
   2  * Copyright (C) 1996-2023 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 #include "squid.h"
  10 #include "base/AsyncJobCalls.h"
  11 #include "base/JobWait.h"
  12
  13 #include <cassert>
  14 #include <iostream>
  15
  16 JobWaitBase::JobWaitBase() = default;
  17
  18 JobWaitBase::~JobWaitBase()
  19 {
  20     cancel("owner gone");
  21 }
  22
  23 void
  24 JobWaitBase::start_(const AsyncJob::Pointer aJob, const AsyncCall::Pointer aCall)
  25 {
  26     // Invariant: The wait will be over. We cannot guarantee that the job will
  27     // call the callback, of course, but we can check these prerequisites.
  28     assert(aCall);
  29     assert(aJob.valid());
  30
  31     // "Double" waiting state leads to conflicting/mismatching callbacks
  32     // detailed in finish(). Detect that bug ASAP.
  33     assert(!waiting());
  34
  35     assert(!callback_);
  36     assert(!job_);
  37     callback_ = aCall;
  38     job_ = aJob;
  39
  40     AsyncJob::Start(job_.get());
  41 }
  42
  43 void
  44 JobWaitBase::finish()
  45 {
  46     // Unexpected callbacks might result in disasters like secrets exposure,
  47     // data corruption, or expensive message routing mistakes when the callback
  48     // info is applied to the wrong message part or acted upon prematurely.
  49     assert(waiting());
  50     clear();
  51 }
  52
  53 void
  54 JobWaitBase::cancel(const char *reason)
  55 {
  56     if (callback_) {
  57         callback_->cancel(reason);
  58
  59         // Instead of AsyncJob, the class parameter could be Job. That would
  60         // avoid runtime child-to-parent CbcPointer conversion overheads, but
  61         // complicate support for Jobs with virtual AsyncJob bases (GCC error:
  62         // "pointer to member conversion via virtual base AsyncJob") and also
  63         // cache-log "Job::handleStopRequest()" with a non-existent class name.
  64         CallJobHere(callback_->debugSection, callback_->debugLevel, job_, AsyncJob, handleStopRequest);
  65
  66         clear();
  67     }
  68 }
  69
  70 void
  71 JobWaitBase::print(std::ostream &os) const
  72 {
  73     // use a backarrow to emphasize that this is a callback: call24<-job6
  74     if (callback_)
  75         os << callback_->id << "<-";
  76     if (const auto rawJob = job_.get())
  77         os << rawJob->id;
  78     else
  79         os << job_; // raw pointer of a gone job may still be useful for triage
  80 }
  81