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hydra-queue-runner: Fix segfault sorting machines by load

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While sorting machines by load, the load of a machine
(machine->currentJobs) can be changed by other threads. If that
happens, the comparator is no longer a proper ordering, in which case
std::sort() can segfault. So we now make a copy of currentJobs before
sorting.
This commit is contained in:
Eelco Dolstra 2015-06-21 16:21:42 +02:00
parent a0eff6fc15
commit d744362e4a
1 changed files with 20 additions and 13 deletions
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33
src/hydra-queue-runner/hydra-queue-runner.cc
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@ -862,12 +862,19 @@ void State::dispatcher()
bool keepGoing;
do {
/* Bail out when there are no slots left. */
std::vector<Machine::ptr> machinesSorted;
/* Copy the currentJobs field of each machine. This is
necessary to ensure that the sort comparator below is a
ordering. std::sort() can segfault if it isn't. */
struct MachineInfo
{
Machine::ptr machine;
unsigned int currentJobs;
};
std::vector<MachineInfo> machinesSorted;
{
auto machines_(machines.lock());
machinesSorted.insert(machinesSorted.end(),
machines_->begin(), machines_->end());
for (auto & m : *machines_)
machinesSorted.push_back({m, m->currentJobs});
}
/* Sort the machines by a combination of speed factor and
@ -882,14 +889,14 @@ void State::dispatcher()
- Finally by load. */
sort(machinesSorted.begin(), machinesSorted.end(),
[](const Machine::ptr & a, const Machine::ptr & b) -> bool
[](const MachineInfo & a, const MachineInfo & b) -> bool
{
float ta = roundf(a->currentJobs / a->speedFactor);
float tb = roundf(b->currentJobs / b->speedFactor);
float ta = roundf(a.currentJobs / a.machine->speedFactor);
float tb = roundf(b.currentJobs / b.machine->speedFactor);
return
ta != tb ? ta < tb :
a->speedFactor != b->speedFactor ? a->speedFactor > b->speedFactor :
a->currentJobs > b->currentJobs;
a.machine->speedFactor != b.machine->speedFactor ? a.machine->speedFactor > b.machine->speedFactor :
a.currentJobs > b.currentJobs;
});
/* Find a machine with a free slot and find a step to run
@ -898,9 +905,9 @@ void State::dispatcher()
keepGoing = false;
system_time now = std::chrono::system_clock::now();
for (auto & machine : machinesSorted) {
for (auto & mi : machinesSorted) {
// FIXME: can we lose a wakeup if a builder exits concurrently?
if (machine->currentJobs >= machine->maxJobs) continue;
if (mi.machine->currentJobs >= mi.machine->maxJobs) continue;
auto runnable_(runnable.lock());
//printMsg(lvlDebug, format("%1% runnable builds") % runnable_->size());
@ -918,7 +925,7 @@ void State::dispatcher()
}
/* Can this machine do this step? */
if (!machine->supportsStep(step)) {
if (!mi.machine->supportsStep(step)) {
++i;
continue;
}
@ -937,7 +944,7 @@ void State::dispatcher()
/* Make a slot reservation and start a thread to
do the build. */
auto reservation = std::make_shared<MachineReservation>(machine);
auto reservation = std::make_shared<MachineReservation>(mi.machine);
i = runnable_->erase(i);
auto builderThread = std::thread(&State::builder, this, step, reservation);