Problems with Linux CommonC++ Thread Class scheduling

[Ian Campbell]

Hello All,
        I have been experimenting with the CommonC++ Thread class on Linux
using the realtime pthread scheduler (either SCHED_RR or SCHED_FIFO) and
found it doesn't work properly in the 1.4.3 release. This fault means that
you can't give seperate threads a different priority from the creating
main process. This is caused by a call to pthread_attr_setinheritsched()
which according to the man page means that the priority and policy for
thread scheduler must be inherited from the creating thread. As such any
subsequent calls to pthread_attr_setschedpolicy() and
pthread_attr_setschedparam() will have no effect. Anyway the patch at the
end of this email should fixeth the problem.

Cheers,

Ian Campbell
Band-X
t: +44 (0) 207 932 8846
f: +44 (0) 207 932 8800
e: address@hidden

diff -u -r CommonC++-1.4.3/posix/thread.cpp
CommonC++-1.4.3-sched.patch/posix/thread.cpp
--- CommonC++-1.4.3/posix/thread.cpp    Thu May 31 08:30:51 2001
+++ CommonC++-1.4.3-sched.patch/posix/thread.cpp        Thu Jun 21
12:41:08 2001
@@ -1,23 +1,23 @@
 // Copyright (C) 1999-2001 Open Source Telecom Corporation.
-//
+//
 // This program is free software; you can redistribute it and/or modify
 // it under the terms of the GNU General Public License as published by
 // the Free Software Foundation; either version 2 of the License, or
 // (at your option) any later version.
-//
+//
 // This program is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 // GNU General Public License for more details.
-//
+//
 // You should have received a copy of the GNU General Public License
-// along with this program; if not, write to the Free Software
+// along with this program; if not, write to the Free Software
 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA.
-//
-// As a special exception to the GNU General Public License, permission
is
-// granted for additional uses of the text contained in its release
+//
+// As a special exception to the GNU General Public License, permission
is
+// granted for additional uses of the text contained in its release
 // of Common C++.
-//
+//
 // The exception is that, if you link the Common C++ library with other
 // files to produce an executable, this does not by itself cause the
 // resulting executable to be covered by the GNU General Public License.
@@ -27,16 +27,16 @@
 // This exception does not however invalidate any other reasons why
 // the executable file might be covered by the GNU General Public
License.
 //
-// This exception applies only to the code released under the
+// This exception applies only to the code released under the
 // name Common C++.  If you copy code from other releases into a copy of
 // Common C++, as the General Public License permits, the exception does
 // not apply to the code that you add in this way.  To avoid misleading
 // anyone as to the status of such modified files, you must delete
 // this exception notice from them.
-//
+//
 // If you write modifications of your own for Common C++, it is your
choice
 // whether to permit this exception to apply to your modifications.
-// If you do not wish that, delete this exception notice.
+// If you do not wish that, delete this exception notice.

 #include "config.h"
 #include "macros.h"
@@ -137,7 +137,7 @@
                sigaction(SIGPOLL, &act, NULL);
 #else
                sigaction(SIGIO, &act, NULL);
-#endif
+#endif

 #ifndef        _SIG_THREAD_STOPCONT
 #ifndef        _THR_SUNOS5
@@ -161,11 +161,11 @@
                sigaddset(&act.sa_mask, SIGPIPE);

                sigaction(_SIG_THREAD_CANCEL, &act, NULL);
-#endif
+#endif
                _main = this;
        }
        _self.setKey(this);
-}
+}

 Thread::Thread(Semaphore *start, int pri, size_t stack)
 {
@@ -176,7 +176,7 @@

        pthread_attr_init(&_attr);
        pthread_attr_setdetachstate(&_attr, PTHREAD_CREATE_JOINABLE);
-       pthread_attr_setinheritsched(&_attr, PTHREAD_INHERIT_SCHED);
+

 #ifdef PTHREAD_STACK_MIN
        if(pthread_attr_setstacksize(&_attr, stack <= PTHREAD_STACK_MIN ?
PTHREAD_STACK_MIN : stack))
@@ -192,7 +192,7 @@
 #endif

 #ifndef        __FreeBSD__
-#ifdef _POSIX_THREAD_PRIORITY_SCHEDULING
+#ifdef _POSIX_THREAD_PRIORITY_SCHEDULING
        if(pri)
        {
                struct sched_param sched;
@@ -220,8 +220,9 @@
                        pri = sched_get_priority_min(policy);

                sched.sched_priority = pri;
+               pthread_attr_setschedpolicy(&_attr, policy);
                pthread_attr_setschedparam(&_attr, &sched);
-       }
+       }
 #endif
 #endif

@@ -289,7 +290,7 @@
        {
                pthread_detach(_tid);
                if(_start)
-               {
+               {
                        _start->Post();
                        return 0;
                }
@@ -351,7 +352,7 @@
                        Thread::_timer->OnTimer();
                }
                else
-#endif
+#endif
                    if(th)
                        th->OnTimer();
                break;
@@ -386,7 +387,7 @@

        if(!setjmp(th->_env))
        {
-               th->Initial();
+               th->Initial();
                if(th->getCancel() == THREAD_CANCEL_INITIAL)
                        th->setCancel(THREAD_CANCEL_DEFAULT);

@@ -411,7 +412,7 @@

 #ifdef HAVE_SETITIMER
        struct itimerval itimer;
-
+
        memset(&itimer, 0, sizeof(itimer));
        itimer.it_value.tv_usec = (timer * 1000) % 1000000;
        itimer.it_value.tv_sec = timer / 1000;
@@ -419,7 +420,7 @@
        timer /= 1000;
 #endif

-#ifndef        _SIG_THREAD_ALARM
+#ifndef        _SIG_THREAD_ALARM
        _arm;
        _timer = this;
 #endif
@@ -432,7 +433,7 @@
 #else
        alarm(timer);
 #endif
-}
+}

 timeout_t Thread::getTimer(void)
 {
@@ -491,7 +492,7 @@
 #else
        sigwait(&mask, &signo);
 #endif
-}
+}

 void   Thread::setSuspend(thread_suspend_t mode)
 {
@@ -518,7 +519,7 @@

        sigemptyset(&mask);
        sigaddset(&mask, _SIG_THREAD_CANCEL);
-
+
        switch(mode)
        {
        case THREAD_CANCEL_IMMEDIATE:
@@ -545,7 +546,7 @@
                pthread_sigmask(SIG_UNBLOCK, &sigs, NULL);
        else
                pthread_sigmask(SIG_BLOCK, &sigs, NULL);
-}
+}

 void   Thread::setCancel(thread_cancel_t mode)
 {
@@ -580,7 +581,7 @@
        sigemptyset(&cancel);
        sigaddset(&cancel, _SIG_THREAD_CANCEL);

-       if(_cancel != THREAD_CANCEL_DISABLED &&
+       if(_cancel != THREAD_CANCEL_DISABLED &&
           _cancel != THREAD_CANCEL_INITIAL)
                pthread_sigmask(SIG_UNBLOCK, &cancel, &old);
 #else
@@ -600,28 +601,28 @@
 {
 #ifdef  _SIG_THREAD_CANCEL
         sigset_t cancel, old;
-
+
         sigemptyset(&cancel);
         sigaddset(&cancel, _SIG_THREAD_CANCEL);
-
+
         if(_cancel != THREAD_CANCEL_DISABLED &&
            _cancel != THREAD_CANCEL_INITIAL)
                 pthread_sigmask(SIG_UNBLOCK, &cancel, &old);
 #else
         pthread_testcancel();
 #endif
-
+
 #ifdef  _SIG_THREAD_CANCEL
         if(_cancel != THREAD_CANCEL_DISABLED)
                 pthread_sigmask(SIG_SETMASK, &old, NULL);
 #endif
-}
+}


 void siginstall(int signo)
 {
        struct sigaction act;
-
+
        act.sa_handler = (signalexec_t)&sigHandler;
        sigemptyset(&act.sa_mask);