#include "debug.h"
-#include <boost/bind.hpp>
+#ifdef _WIN32
+# include <sstream>
+# include <windows.h>
-#include <cerrno>
-#include <cstdlib>
-#ifdef HAVE_UNISTD_H
+#else
+# include <cerrno>
+# include <cstdlib>
# include <unistd.h>
+# include <sys/wait.h>
+
+# ifndef CXX_GLOBAL_CSTD
+ using std::signal;
+ using std::strerror;
+# endif
#endif
-#include <sys/wait.h>
+
+#include <boost/bind.hpp>
using boost::bind;
using std::string;
using std::vector;
-#ifndef CXX_GLOBAL_CSTD
-using std::signal;
-using std::strerror;
-#endif
-
-
namespace lyx {
namespace support {
-/* The forkedcall controller code handles finished child processes in a
- two-stage process.
-
- 1. It uses the SIGCHLD signal emitted by the system when the child process
- finishes to reap the resulting zombie. The handler routine also
- updates an internal list of completed children.
- 2. The signals associated with these completed children are then emitted
- as part of the main LyX event loop.
-
- The guiding philosophy is that zombies are a global resource that should
- be reaped as soon as possible whereas an internal list of dead children
- is not. Indeed, to emit the signals within the asynchronous handler
- routine would result in unsafe code.
-
- The signal handler is guaranteed to be safe even though it may not be
- atomic:
-
- int completed_child_status;
- sig_atomic_t completed_child_pid;
-
- extern "C"
- void child_handler(int)
- {
- // Clean up the child process.
- completed_child_pid = wait(&completed_child_status);
- }
-
- (See the signals tutorial at http://tinyurl.com/3h82w.)
-
- It's safe because:
- 1. wait(2) is guaranteed to be async-safe.
- 2. child_handler handles only SIGCHLD signals so all subsequent
- SIGCHLD signals are blocked from entering the handler until the
- existing signal is processed.
-
- This handler performs 'half' of the necessary clean up after a
- completed child process. It prevents us leaving a stream of zombies
- behind but does not go on to tell the main LyX program to finish the
- clean-up by emitting the stored signal. That would most definitely
- not be safe.
-
- The only problem with the above is that the global stores
- completed_child_status, completed_child_pid may be overwritten before
- the clean-up is completed in the main loop.
-
- However, the code in child_handler can be extended to fill an array of
- completed processes. Everything remains safe so long as no 'unsafe'
- functions are called. (See the list of async-safe functions at
- http://tinyurl.com/3h82w.)
-
- struct child_data {
- pid_t pid;
- int status;
- };
-
- // This variable may need to be resized in the main program
- // as and when a new process is forked. This resizing must be
- // protected with sigprocmask
- std::vector<child_data> reaped_children;
- sig_atomic_t current_child = -1;
-
- extern "C"
- void child_handler(int)
- {
- child_data & store = reaped_children[++current_child];
- // Clean up the child process.
- store.pid = wait(&store.status);
- }
-
- That is, we build up a list of completed children in anticipation of
- the main loop then looping over this list and invoking any associated
- callbacks etc. The nice thing is that the main loop needs only to
- check the value of 'current_child':
-
- if (current_child != -1)
- handleCompletedProcesses();
-
- handleCompletedProcesses now loops over only those child processes
- that have completed (ie, those stored in reaped_children). It blocks
- any subsequent SIGCHLD signal whilst it does so:
-
- // Used to block SIGCHLD signals.
- sigset_t newMask, oldMask;
-
- ForkedcallsController::ForkedcallsController()
- {
- reaped_children.resize(50);
- signal(SIGCHLD, child_handler);
-
- sigemptyset(&oldMask);
- sigemptyset(&newMask);
- sigaddset(&newMask, SIGCHLD);
- }
-
- void ForkedcallsController::handleCompletedProcesses()
- {
- if (current_child == -1)
- return;
-
- // Block the SIGCHLD signal.
- sigprocmask(SIG_BLOCK, &newMask, &oldMask);
-
- for (int i = 0; i != 1+current_child; ++i) {
- child_data & store = reaped_children[i];
- // Go on to handle the child process
- ...
- }
-
- // Unblock the SIGCHLD signal and restore the old mask.
- sigprocmask(SIG_SETMASK, &oldMask, 0);
- }
-
- Voilà! An efficient, elegant and *safe* mechanism to handle child processes.
-*/
-
-namespace {
-
-extern "C"
-void child_handler(int)
+#if defined(_WIN32)
+string const getChildErrorMessage()
{
- ForkedcallsController & fcc = ForkedcallsController::get();
-
- // Be safe
- typedef vector<ForkedcallsController::Data>::size_type size_type;
- if (size_type(fcc.current_child + 1) >= fcc.reaped_children.size())
- return;
-
- ForkedcallsController::Data & store =
- fcc.reaped_children[++fcc.current_child];
- // Clean up the child process.
- store.pid = wait(&store.status);
+ DWORD const error_code = ::GetLastError();
+
+ HLOCAL t_message = 0;
+ bool const ok = ::FormatMessage(
+ FORMAT_MESSAGE_ALLOCATE_BUFFER |
+ FORMAT_MESSAGE_FROM_SYSTEM,
+ 0, error_code,
+ MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+ (LPTSTR) &t_message, 0, 0
+ ) != 0;
+
+ std::ostringstream ss;
+ ss << "LyX: Error waiting for child: " << error_code;
+
+ if (ok) {
+ ss << ": " << (LPTSTR)t_message;
+ ::LocalFree(t_message);
+ } else
+ ss << ": Error unknown.";
+
+ return ss.str().c_str();
}
-
-} // namespace anon
+#endif
// Ensure, that only one controller exists inside process
ForkedcallsController::ForkedcallsController()
- : reaped_children(50), current_child(-1)
-{
- signal(SIGCHLD, child_handler);
-
- sigemptyset(&oldMask);
- sigemptyset(&newMask);
- sigaddset(&newMask, SIGCHLD);
-}
+{}
// open question: should we stop childs here?
// Asger says no: I like to have my xdvi open after closing LyX. Maybe
// I want to print or something.
ForkedcallsController::~ForkedcallsController()
-{
- signal(SIGCHLD, SIG_DFL);
-}
+{}
void ForkedcallsController::addCall(ForkedProcess const & newcall)
{
forkedCalls.push_back(newcall.clone());
-
- if (forkedCalls.size() > reaped_children.size()) {
- // Block the SIGCHLD signal.
- sigprocmask(SIG_BLOCK, &newMask, &oldMask);
-
- reaped_children.resize(2*reaped_children.size());
-
- // Unblock the SIGCHLD signal and restore the old mask.
- sigprocmask(SIG_SETMASK, &oldMask, 0);
- }
-}
-
-
-ForkedcallsController::iterator
- ForkedcallsController::find_pid(pid_t pid)
-{
- return find_if(forkedCalls.begin(), forkedCalls.end(),
- bind(equal_to<pid_t>(),
- bind(&Forkedcall::pid, _1),
- pid));
-}
-
-
-// Kill the process prematurely and remove it from the list
-// within tolerance secs
-void ForkedcallsController::kill(pid_t pid, int tolerance)
-{
- ListType::iterator it = find_pid(pid);
- if (it == forkedCalls.end())
- return;
-
- (*it)->kill(tolerance);
- forkedCalls.erase(it);
}
// Check the list of dead children and emit any associated signals.
void ForkedcallsController::handleCompletedProcesses()
{
- if (current_child == -1)
- return;
-
- // Block the SIGCHLD signal.
- sigprocmask(SIG_BLOCK, &newMask, &oldMask);
-
- for (int i = 0; i != 1 + current_child; ++i) {
- Data & store = reaped_children[i];
+ ListType::iterator it = forkedCalls.begin();
+ ListType::iterator end = forkedCalls.end();
+ while (it != end) {
+ ForkedProcessPtr actCall = *it;
+ bool remove_it = false;
- if (store.pid == -1) {
- // Might happen perfectly innocently, eg as a result
- // of the system (3) call.
- if (errno)
- lyxerr << "LyX: Error waiting for child: "
- << strerror(errno) << endl;
- continue;
+#if defined(_WIN32)
+ HANDLE const hProcess = HANDLE(actCall->pid());
+
+ DWORD const wait_status = ::WaitForSingleObject(hProcess, 0);
+
+ switch (wait_status) {
+ case WAIT_TIMEOUT:
+ // Still running
+ break;
+ case WAIT_OBJECT_0: {
+ DWORD exit_code = 0;
+ if (!GetExitCodeProcess(hProcess, &exit_code)) {
+ lyxerr << "GetExitCodeProcess failed waiting for child\n"
+ << getChildErrorMessage() << std::endl;
+ // Child died, so pretend it returned 1
+ actCall->setRetValue(1);
+ } else {
+ actCall->setRetValue(exit_code);
+ }
+ remove_it = true;
+ break;
}
+ case WAIT_FAILED:
+ lyxerr << "WaitForSingleObject failed waiting for child\n"
+ << getChildErrorMessage() << std::endl;
+ actCall->setRetValue(1);
+ remove_it = true;
+ break;
+ }
+#else
+ pid_t pid = actCall->pid();
+ int stat_loc;
+ pid_t const waitrpid = waitpid(pid, &stat_loc, WNOHANG);
- ListType::iterator it = find_pid(store.pid);
- if (it == forkedCalls.end())
- // Eg, child was run in blocking mode
- continue;
+ if (waitrpid == -1) {
+ lyxerr << "LyX: Error waiting for child: "
+ << strerror(errno) << endl;
- ListType::value_type child = (*it);
- bool remove_it = false;
+ // Child died, so pretend it returned 1
+ actCall->setRetValue(1);
+ remove_it = true;
+
+ } else if (waitrpid == 0) {
+ // Still running. Move on to the next child.
- if (WIFEXITED(store.status)) {
+ } else if (WIFEXITED(stat_loc)) {
// Ok, the return value goes into retval.
- child->setRetValue(WEXITSTATUS(store.status));
+ actCall->setRetValue(WEXITSTATUS(stat_loc));
remove_it = true;
- } else if (WIFSIGNALED(store.status)) {
+ } else if (WIFSIGNALED(stat_loc)) {
// Child died, so pretend it returned 1
- child->setRetValue(1);
+ actCall->setRetValue(1);
remove_it = true;
- } else if (WIFSTOPPED(store.status)) {
- lyxerr << "LyX: Child (pid: " << store.pid
+ } else if (WIFSTOPPED(stat_loc)) {
+ lyxerr << "LyX: Child (pid: " << pid
<< ") stopped on signal "
- << WSTOPSIG(store.status)
+ << WSTOPSIG(stat_loc)
<< ". Waiting for child to finish." << endl;
} else {
lyxerr << "LyX: Something rotten happened while "
- << "waiting for child " << store.pid << endl;
+ "waiting for child " << pid << endl;
// Child died, so pretend it returned 1
- child->setRetValue(1);
+ actCall->setRetValue(1);
remove_it = true;
}
+#endif
if (remove_it) {
- child->emitSignal();
forkedCalls.erase(it);
+ actCall->emitSignal();
+
+ /* start all over: emiting the signal can result
+ * in changing the list (Ab)
+ */
+ it = forkedCalls.begin();
+ } else {
+ ++it;
}
}
+}
- // Reset the counter
- current_child = -1;
- // Unblock the SIGCHLD signal and restore the old mask.
- sigprocmask(SIG_SETMASK, &oldMask, 0);
+ForkedcallsController::iterator
+ForkedcallsController::find_pid(pid_t pid)
+{
+ return find_if(forkedCalls.begin(), forkedCalls.end(),
+ bind(equal_to<pid_t>(),
+ bind(&Forkedcall::pid, _1),
+ pid));
+}
+
+
+// Kill the process prematurely and remove it from the list
+// within tolerance secs
+void ForkedcallsController::kill(pid_t pid, int tolerance)
+{
+ ListType::iterator it = find_pid(pid);
+ if (it == forkedCalls.end())
+ return;
+
+ (*it)->kill(tolerance);
+ forkedCalls.erase(it);
}
} // namespace support
projects / features.git / commitdiff