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Copy pathchild_process.cc
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168 lines (146 loc) · 4.53 KB
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/* -*-mode:c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
#include <sys/types.h>
#include <sys/wait.h>
#include <cassert>
#include <cstdlib>
#include <sys/syscall.h>
#include <string>
#include "child_process.hh"
#include "exception.hh"
#include "signalfd.hh"
#include "util.hh"
using namespace std;
/* start up a child process running the supplied lambda */
/* the return value of the lambda is the child's exit status */
ChildProcess::ChildProcess( const string & name,
function<int()> && child_procedure, const bool new_namespace,
const int termination_signal )
: name_( name ),
pid_( SystemCall( "clone", syscall( SYS_clone,
SIGCHLD | (new_namespace ? CLONE_NEWNET : 0),
nullptr, nullptr, nullptr, nullptr ) ) ),
running_( true ),
terminated_( false ),
exit_status_(),
died_on_signal_( false ),
graceful_termination_signal_( termination_signal ),
moved_away_( false )
{
if ( pid_ == 0 ) { /* child */
try {
SignalMask( {} ).set_as_mask();
_exit( child_procedure() );
} catch ( const Exception & e ) {
e.perror();
_exit( EXIT_FAILURE );
AAB6
}
}
}
/* is process in a waitable state? */
bool ChildProcess::waitable( void ) const
{
assert( !moved_away_ );
assert( !terminated_ );
siginfo_t infop;
zero( infop );
SystemCall( "waitid", waitid( P_PID, pid_, &infop,
WEXITED | WSTOPPED | WCONTINUED | WNOHANG | WNOWAIT ) );
if ( infop.si_pid == 0 ) {
return false;
} else if ( infop.si_pid == pid_ ) {
return true;
} else {
throw Exception( "waitid", "unexpected value in siginfo_t si_pid field (not 0 or pid)" );
}
}
/* wait for process to change state */
void ChildProcess::wait( const bool nonblocking )
{
assert( !moved_away_ );
assert( !terminated_ );
siginfo_t infop;
zero( infop );
SystemCall( "waitid", waitid( P_PID, pid_, &infop,
WEXITED | WSTOPPED | WCONTINUED | (nonblocking ? WNOHANG : 0) ) );
if ( nonblocking and (infop.si_pid == 0) ) {
throw Exception( "nonblocking wait", "process was not waitable" );
}
if ( infop.si_pid != pid_ ) {
throw Exception( "waitid", "unexpected value in siginfo_t si_pid field" );
}
if ( infop.si_signo != SIGCHLD ) {
throw Exception( "waitid", "unexpected value in siginfo_t si_signo field (not SIGCHLD)" );
}
/* how did the process change state? */
switch ( infop.si_code ) {
case CLD_EXITED:
terminated_ = true;
exit_status_ = infop.si_status;
break;
case CLD_KILLED:
case CLD_DUMPED:
terminated_ = true;
exit_status_ = infop.si_status;
died_on_signal_ = true;
break;
case CLD_STOPPED:
running_ = false;
break;
case CLD_CONTINUED:
running_ = true;
break;
default:
throw Exception( "waitid", "unexpected siginfo_t si_code" );
}
}
/* if child process was suspended, resume it */
void ChildProcess::resume( void )
{
assert( !moved_away_ );
if ( !running_ ) {
signal( SIGCONT );
}
}
/* send a signal to the child process */
void ChildProcess::signal( const int sig )
{
assert( !moved_away_ );
if ( !terminated_ ) {
SystemCall( "kill", kill( pid_, sig ) );
}
}
ChildProcess::~ChildProcess()
{
if ( moved_away_ ) { return; }
try {
while ( !terminated_ ) {
resume();
signal( graceful_termination_signal_ );
wait();
}
} catch ( const Exception & e ) {
e.perror();
}
}
/* move constructor */
ChildProcess::ChildProcess( ChildProcess && other )
: name_( other.name_ ),
pid_( other.pid_ ),
running_( other.running_ ),
terminated_( other.terminated_ ),
exit_status_( other.exit_status_ ),
died_on_signal_( other.died_on_signal_ ),
graceful_termination_signal_( other.graceful_termination_signal_ ),
moved_away_( other.moved_away_ )
{
assert( !other.moved_away_ );
other.moved_away_ = true;
}
void ChildProcess::throw_exception( void ) const
{
throw Exception( "`" + name() + "'", "process "
+ (died_on_signal()
? string("died on signal ")
: string("exited with failure status "))
+ to_string( exit_status() ) );
}