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* Goal cancellation inside the waitForInput() loop needs to be handled

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very carefully, since it can invalidate iterators into the
  `children' map.
This commit is contained in:
Eelco Dolstra 2006-12-08 18:41:48 +00:00
parent 06c4929958
commit fa33303146
1 changed files with 85 additions and 38 deletions
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123
src/libstore/build.cc
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@ -123,10 +123,10 @@ public:
return exitCode;
}
void cancel()
{
amDone(ecFailed);
}
/* Cancel the goal. It should wake up its waiters, get rid of any
running child processes that are being monitored by the worker
(important!), etc. */
virtual void cancel() = 0;
protected:
void amDone(ExitCode result);
@ -592,6 +592,8 @@ public:
DerivationGoal(const Path & drvPath, Worker & worker);
~DerivationGoal();
void cancel();
void work();
Path getDrvPath()
@ -646,6 +648,9 @@ private:
/* Return the set of (in)valid paths. */
PathSet checkPathValidity(bool returnValid);
/* Forcibly kill the child process, if any. */
void killChild();
};
@ -664,36 +669,48 @@ DerivationGoal::~DerivationGoal()
/* Careful: we should never ever throw an exception from a
destructor. */
try {
if (pid != -1) {
worker.childTerminated(pid);
if (buildUser.enabled()) {
/* Note that we can't let pid's destructor kill the
the child process, since it may not have the
appropriate privilege (i.e., the setuid helper
should do it).
However, if we're using a build user, then there is
a tricky race condition: if we kill the build user
before the child has done its setuid() to the build
user uid, then it won't be killed, and we'll
potentially lock up in pid.wait(). So also send a
conventional kill to the child. */
::kill(-pid, SIGKILL); /* ignore the result */
buildUser.kill();
pid.wait(true);
assert(pid == -1);
}
}
killChild();
deleteTmpDir(false);
} catch (Error & e) {
printMsg(lvlError, format("error (ignored): %1%") % e.msg());
}
}
void DerivationGoal::killChild()
{
if (pid != -1) {
worker.childTerminated(pid);
if (buildUser.enabled()) {
/* We can't use pid.kill(), since we may not have the
appropriate privilege. I.e., if we're not root, then
setuid helper should do it).
Also, if we're using a build user, then there is a
tricky race condition: if we kill the build user before
the child has done its setuid() to the build user uid,
then it won't be killed, and we'll potentially lock up
in pid.wait(). So also send a conventional kill to the
child. */
::kill(-pid, SIGKILL); /* ignore the result */
buildUser.kill();
pid.wait(true);
} else
pid.kill();
assert(pid == -1);
}
}
void DerivationGoal::cancel()
{
killChild();
amDone(ecFailed);
}
void DerivationGoal::work()
{
(this->*state)();
@ -1813,6 +1830,8 @@ public:
SubstitutionGoal(const Path & storePath, Worker & worker);
~SubstitutionGoal();
void cancel();
void work();
/* The states. */
@ -1840,10 +1859,24 @@ SubstitutionGoal::SubstitutionGoal(const Path & storePath, Worker & worker)
SubstitutionGoal::~SubstitutionGoal()
{
/* !!! Once we let substitution goals run under a build user, we
need to do use the setuid helper just as in ~DerivationGoal().
Idem for cancel. */
if (pid != -1) worker.childTerminated(pid);
}
void SubstitutionGoal::cancel()
{
if (pid != -1) {
pid_t savedPid = pid;
pid.kill();
worker.childTerminated(savedPid);
}
amDone(ecFailed);
}
void SubstitutionGoal::work()
{
(this->*state)();
@ -2189,6 +2222,8 @@ void Worker::childStarted(GoalPtr goal,
void Worker::childTerminated(pid_t pid, bool wakeSleepers)
{
assert(pid != -1); /* common mistake */
Children::iterator i = children.find(pid);
assert(i != children.end());
@ -2329,38 +2364,50 @@ void Worker::waitForInput()
time_t now = time(0);
/* Process all available file descriptors. */
/* Since goals may be canceled from inside the loop below (causing
them go be erased from the `children' map), we have to be
careful that we don't keep iterators alive across calls to
cancel(). */
set<pid_t> pids;
for (Children::iterator i = children.begin();
i != children.end(); ++i)
pids.insert(i->first);
for (set<pid_t>::iterator i = pids.begin();
i != pids.end(); ++i)
{
checkInterrupt();
GoalPtr goal = i->second.goal.lock();
Children::iterator j = children.find(*i);
if (j == children.end()) continue; // child destroyed
GoalPtr goal = j->second.goal.lock();
assert(goal);
set<int> fds2(i->second.fds);
for (set<int>::iterator j = fds2.begin(); j != fds2.end(); ++j) {
if (FD_ISSET(*j, &fds)) {
set<int> fds2(j->second.fds);
for (set<int>::iterator k = fds2.begin(); k != fds2.end(); ++k) {
if (FD_ISSET(*k, &fds)) {
unsigned char buffer[4096];
ssize_t rd = read(*j, buffer, sizeof(buffer));
ssize_t rd = read(*k, buffer, sizeof(buffer));
if (rd == -1) {
if (errno != EINTR)
throw SysError(format("reading from %1%")
% goal->getName());
} else if (rd == 0) {
debug(format("%1%: got EOF") % goal->getName());
goal->handleEOF(*j);
i->second.fds.erase(*j);
goal->handleEOF(*k);
j->second.fds.erase(*k);
} else {
printMsg(lvlVomit, format("%1%: read %2% bytes")
% goal->getName() % rd);
string data((char *) buffer, rd);
goal->handleChildOutput(*j, data);
i->second.lastOutput = now;
goal->handleChildOutput(*k, data);
j->second.lastOutput = now;
}
}
}
if (maxSilentTime != 0 &&
now - i->second.lastOutput >= (time_t) maxSilentTime)
now - j->second.lastOutput >= (time_t) maxSilentTime)
{
printMsg(lvlError,
format("%1% timed out after %2% seconds of silence")