Our ForkedcallsController class currently uses a Timeout variable to
initiate checks for any completed child processes every 100ms. This
is conceptually ugly, as it requires us to use the GUI libraries and
will prevent forked calls working correctly when the GUI event loop
is not started. (Ie, lyx --export). That isn't a problem now, but it
might become one in the future. And anyway it's ugly.
Attached is a patch to use the SIGCHLD signal instead of this Timeout. The
patch is against the 13x tree which is what I have available here at
work. (I'm not proposing adding this patch to LyX 13x.) As
proof-of-concept, it seems to work perfectly.
This is my first go at using the SIGFOO family, so I'd value it if
someone more knowledgable took a look. Specifically, will this code
work if a SIGCHLD signal is received whilst we're still processing a
previous SIGCHLD signal in ForkedcallsController::timer()?
static void child_handler(int err_sig)
{
switch (err_sig) {
case SIGCHLD:
lyxerr << "\nlyx: SIGCHLD signal caught" << endl;
ForkedcallsController::get().timer();
break;
default:
lyxerr << "\nlyx: warning! Unexpected signal caught!"
<< err_sig << endl;
}
}
void LyX::init(bool gui)
{
signal(SIGCHLD, child_handler);
...
}
Or should the code in child_handler be truly trivial:
static bool sigchild_received = false;
static void child_handler(int err_sig)
{
switch (err_sig) {
case SIGCHLD:
sigchild_received = true;
break;
default:
lyxerr << "\nlyx: warning! Unexpected signal caught!"
<< err_sig << endl;
}
}
Leaving the handling of sigchild_received to someplace outside of the
handler?
Angus
? build-qt
? build-xforms
? sigchld.diff
Index: src/lyx_main.C
===================================================================
RCS file: /usr/local/lyx/cvsroot/lyx-devel/src/lyx_main.C,v
retrieving revision 1.134.2.2
diff -u -p -r1.134.2.2 lyx_main.C
--- src/lyx_main.C 12 Feb 2004 17:18:02 -0000 1.134.2.2
+++ src/lyx_main.C 19 Mar 2004 17:49:08 -0000
@@ -16,6 +16,7 @@
#include "lyx_main.h"
#include "support/filetools.h"
+#include "support/forkedcontr.h"
#include "support/lyxlib.h"
#include "support/os.h"
#include "support/FileInfo.h"
@@ -169,6 +170,19 @@ LyX::LyX(int & argc, char * argv[])
extern "C" {
+static void child_handler(int err_sig)
+{
+ switch (err_sig) {
+ case SIGCHLD:
+ lyxerr << "\nlyx: SIGCHLD signal caught" << endl;
+ ForkedcallsController::get().timer();
+ break;
+ default:
+ lyxerr << "\nlyx: warning! Unexpected signal caught!"
+ << err_sig << endl;
+ }
+}
+
static void error_handler(int err_sig)
{
switch (err_sig) {
@@ -195,6 +209,7 @@ static void error_handler(int err_sig)
}
// Deinstall the signal handlers
+ signal(SIGCHLD, SIG_DFL);
signal(SIGHUP, SIG_DFL);
signal(SIGINT, SIG_DFL);
signal(SIGFPE, SIG_DFL);
@@ -215,6 +230,7 @@ static void error_handler(int err_sig)
void LyX::init(bool gui)
{
+ signal(SIGCHLD, child_handler);
signal(SIGHUP, error_handler);
signal(SIGFPE, error_handler);
signal(SIGSEGV, error_handler);
Index: src/support/forkedcontr.C
===================================================================
RCS file: /usr/local/lyx/cvsroot/lyx-devel/src/support/forkedcontr.C,v
retrieving revision 1.6.2.2
diff -u -p -r1.6.2.2 forkedcontr.C
--- src/support/forkedcontr.C 7 Mar 2003 15:43:58 -0000 1.6.2.2
+++ src/support/forkedcontr.C 19 Mar 2004 17:49:09 -0000
@@ -50,10 +50,12 @@ ForkedcallsController & ForkedcallsContr
ForkedcallsController::ForkedcallsController()
{
+#if 0
timeout_ = new Timeout(100, Timeout::ONETIME);
timeout_->timeout
.connect(boost::bind(&ForkedcallsController::timer, this));
+#endif
}
@@ -67,14 +69,18 @@ ForkedcallsController::~ForkedcallsContr
delete *it;
}
+#if 0
delete timeout_;
+#endif
}
void ForkedcallsController::addCall(ForkedProcess const & newcall)
{
+#if 0
if (!timeout_->running())
timeout_->start();
+#endif
forkedCalls.push_back(newcall.clone());
childrenChanged();
@@ -85,6 +91,7 @@ void ForkedcallsController::addCall(Fork
// Check the list and, if there is a stopped child, emit the signal.
void ForkedcallsController::timer()
{
+ lyxerr << "Entered ForkedcallsController::timer()" << endl;
ListType::size_type start_size = forkedCalls.size();
ListType::iterator it = forkedCalls.begin();
@@ -148,12 +155,15 @@ void ForkedcallsController::timer()
}
}
+#if 0
if (!forkedCalls.empty() && !timeout_->running()) {
timeout_->start();
}
+#endif
if (start_size != forkedCalls.size())
childrenChanged();
+ lyxerr << "Leaving ForkedcallsController::timer()" << endl;
}
@@ -206,7 +216,9 @@ void ForkedcallsController::kill(pid_t p
(*it)->kill(tolerance);
forkedCalls.erase(it);
+#if 0
if (forkedCalls.empty()) {
timeout_->stop();
}
+#endif
}
