src/support/forkedcall.C

   1 /**
   2  *  \file forkedcall.C
   3  * This file is part of LyX, the document processor.
   4  * Licence details can be found in the file COPYING.
   5  *
   6  * \author Asger Alstrup
   7  *
   8  * Interface cleaned up by
   9  * \author Angus Leeming
  10  *
  11  * Full author contact details are available in file CREDITS
  12  *
  13  * An instance of Class Forkedcall represents a single child process.
  14  *
  15  * Class Forkedcall uses fork() and execvp() to lauch the child process.
  16  *
  17  * Once launched, control is returned immediately to the parent process
  18  * but a Signal can be emitted upon completion of the child.
  19  *
  20  * The child process is not killed when the Forkedcall instance goes out of
  21  * scope, but it can be killed by an explicit invocation of the kill() member
  22  * function.
  23  */
  24
  25 #include <config.h>
  26
  27 #ifdef __GNUG__
  28 #pragma implementation
  29 #endif
  30
  31 #include "forkedcall.h"
  32 #include "forkedcontr.h"
  33 #include "lstrings.h"
  34 #include "lyxlib.h"
  35 #include "filetools.h"
  36 #include "os.h"
  37 #include "debug.h"
  38 #include "frontends/Timeout.h"
  39
  40 #include <boost/bind.hpp>
  41
  42 #include <cerrno>
  43 #include <sys/types.h>
  44 #include <sys/wait.h>
  45 #include <csignal>
  46 #include <cstdlib>
  47 #include <unistd.h>
  48
  49 using std::endl;
  50
  51 #ifndef CXX_GLOBAL_CSTD
  52 using std::strerror;
  53 #endif
  54
  55
  56 Forkedcall::Forkedcall()
  57         : pid_(0), retval_(0)
  58 {}
  59
  60
  61 int Forkedcall::startscript(Starttype wait, string const & what)
  62 {
  63         if (wait == Wait) {
  64                 command_ = what;
  65                 retval_  = 0;
  66
  67                 pid_ = generateChild();
  68                 if (pid_ <= 0) { // child or fork failed.
  69                         retval_ = 1;
  70                 } else {
  71                         retval_ = waitForChild();
  72                 }
  73
  74                 return retval_;
  75         }
  76
  77         // DontWait
  78         retval_ = startscript(what, SignalTypePtr());
  79         return retval_;
  80 }
  81
  82
  83 int Forkedcall::startscript(string const & what, SignalTypePtr signal)
  84 {
  85         command_ = what;
  86         signal_  = signal;
  87         retval_  = 0;
  88
  89         pid_ = generateChild();
  90         if (pid_ <= 0) { // child or fork failed.
  91                 retval_ = 1;
  92                 return retval_;
  93         }
  94
  95         // Non-blocking execution.
  96         // Integrate into the Controller
  97         ForkedcallsController & contr = ForkedcallsController::get();
  98         contr.addCall(*this);
  99
 100         return retval_;
 101 }
 102
 103
 104 void Forkedcall::emitSignal()
 105 {
 106         if (signal_.get()) {
 107                 signal_->operator()(command_, pid_, retval_);
 108         }
 109 }
 110
 111
 112 namespace {
 113
 114 class Murder : public boost::signals::trackable {
 115 public:
 116         //
 117         static void killItDead(int secs, pid_t pid)
 118         {
 119                 if (secs > 0) {
 120                         new Murder(secs, pid);
 121                 } else if (pid != 0) {
 122                         lyx::kill(pid, SIGKILL);
 123                 }
 124         }
 125
 126         //
 127         void kill()
 128         {
 129                 if (pid_ != 0) {
 130                         lyx::kill(pid_, SIGKILL);
 131                 }
 132                 lyxerr << "Killed " << pid_ << std::endl;
 133                 delete this;
 134         }
 135
 136 private:
 137         //
 138         Murder(int secs, pid_t pid)
 139                 : timeout_(0), pid_(pid)
 140         {
 141                 timeout_ = new Timeout(1000*secs, Timeout::ONETIME);
 142                 timeout_->timeout.connect(boost::bind(&Murder::kill, this));
 143                 timeout_->start();
 144         }
 145
 146         //
 147         ~Murder()
 148         {
 149                 delete timeout_;
 150         }
 151         //
 152         Timeout * timeout_;
 153         //
 154         pid_t pid_;
 155 };
 156
 157 } // namespace anon
 158
 159
 160 void Forkedcall::kill(int tol)
 161 {
 162         lyxerr << "Forkedcall::kill(" << tol << ")" << std::endl;
 163         if (pid() == 0) {
 164                 lyxerr << "Can't kill non-existent process!" << endl;
 165                 return;
 166         }
 167
 168         int const tolerance = std::max(0, tol);
 169         if (tolerance == 0) {
 170                 // Kill it dead NOW!
 171                 Murder::killItDead(0, pid());
 172
 173         } else {
 174                 int ret = lyx::kill(pid(), SIGHUP);
 175
 176                 // The process is already dead if wait_for_death is false
 177                 bool const wait_for_death = (ret == 0 && errno != ESRCH);
 178
 179                 if (wait_for_death) {
 180                         Murder::killItDead(tolerance, pid());
 181                 }
 182         }
 183 }
 184
 185
 186 // Wait for child process to finish. Returns returncode from child.
 187 int Forkedcall::waitForChild() {
 188         // We'll pretend that the child returns 1 on all error conditions.
 189         retval_ = 1;
 190         int status;
 191         bool wait = true;
 192         while (wait) {
 193                 pid_t waitrpid = waitpid(pid_, &status, WUNTRACED);
 194                 if (waitrpid == -1) {
 195                         lyxerr << "LyX: Error waiting for child:"
 196                                << strerror(errno) << endl;
 197                         wait = false;
 198                 } else if (WIFEXITED(status)) {
 199                         // Child exited normally. Update return value.
 200                         retval_ = WEXITSTATUS(status);
 201                         wait = false;
 202                 } else if (WIFSIGNALED(status)) {
 203                         lyxerr << "LyX: Child didn't catch signal "
 204                                << WTERMSIG(status)
 205                                << "and died. Too bad." << endl;
 206                         wait = false;
 207                 } else if (WIFSTOPPED(status)) {
 208                         lyxerr << "LyX: Child (pid: " << pid_
 209                                << ") stopped on signal "
 210                                << WSTOPSIG(status)
 211                                << ". Waiting for child to finish." << endl;
 212                 } else {
 213                         lyxerr << "LyX: Something rotten happened while "
 214                                 "waiting for child " << pid_ << endl;
 215                         wait = false;
 216                 }
 217         }
 218         return retval_;
 219 }
 220
 221
 222 // generate child in background
 223 pid_t Forkedcall::generateChild()
 224 {
 225         const int MAX_ARGV = 255;
 226         char *syscmd = 0;
 227         char *argv[MAX_ARGV];
 228
 229         string childcommand(command_); // copy
 230         bool more = true;
 231         string rest = split(command_, childcommand, ' ');
 232
 233         int  index = 0;
 234         while (more) {
 235                 childcommand = ltrim(childcommand);
 236                 if (syscmd == 0) {
 237                         syscmd = new char[childcommand.length() + 1];
 238                         childcommand.copy(syscmd, childcommand.length());
 239                         syscmd[childcommand.length()] = '\0';
 240                 }
 241                 if (!childcommand.empty()) {
 242                         char * tmp = new char[childcommand.length() + 1];
 243                         childcommand.copy(tmp, childcommand.length());
 244                         tmp[childcommand.length()] = '\0';
 245                         argv[index++] = tmp;
 246                 }
 247
 248                 // reinit
 249                 more = !rest.empty();
 250                 if (more)
 251                         rest = split(rest, childcommand, ' ');
 252         }
 253         argv[index] = 0;
 254
 255 #ifndef __EMX__
 256         pid_t cpid = ::fork();
 257         if (cpid == 0) { // child
 258                 execvp(syscmd, argv);
 259                 // If something goes wrong, we end up here
 260                 string args;
 261                 int i = 0;
 262                 while (argv[i] != 0)
 263                         args += string(" ") + argv[i++];
 264                 lyxerr << "execvp of \"" << syscmd << args << "\" failed: "
 265                        << strerror(errno) << endl;
 266         }
 267 #else
 268         pid_t cpid = spawnvp(P_SESSION|P_DEFAULT|P_MINIMIZE|P_BACKGROUND,
 269                              syscmd, argv);
 270 #endif
 271
 272         if (cpid < 0) { // error
 273                 lyxerr << "Could not fork: "
 274                        << strerror(errno) << endl;
 275         }
 276
 277         return cpid;
 278 }