[Xenomai-help] kernel oops using mq_open after fork

[Xenomai-help] kernel oops using mq_open after fork

[Landau, Bracha]

I'm using xenomai 2.2 rc3 on a MPC8247, on linux 2.6.14.
 
I have a problem using mq_open. Please see the attached code.
If I fork before the mq_open the kernel, I get a kernel oops.

Why this behaviour?

//***************************************************************
#include <termios.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/select.h>
#include <error.h>
#include <errno.h>

#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <time.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <sys/time.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/mount.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <pthread.h>
#include <unistd.h>
#include <mqueue.h>
#include <sys/mman.h>
pthread_t Main_Exec_thread_id;


#define MAIN_TASK_PRI 20
#define MAIN_STACK_SIZE 8192

pthread_attr_t Main_Exec_attr;
struct sched_param Main_Exec_parm;

int Main_PID = 0;
int Mains_Parent = 0;
int Child_PID = 0;

void split (void);

void *MainExecThread (void *dummy)
{

  	struct mq_attr buf;
	int perms = 0666;
	buf.mq_msgsize = 4;
	buf.mq_maxmsg = 20;
	printf ("mq_open\n");
	sleep (2);
	mq_open ("/con_to_R01", O_CREAT | O_RDWR , perms, &buf);

	pause ();

	return 0;

}

int child (void)
{

	Main_PID = getpid ();

	printf ("main pid = %08x\n", Main_PID) ;
	printf ("main parent = %08x\n", Mains_Parent);


	mlockall (MCL_CURRENT | MCL_FUTURE);

	pthread_attr_init (&Main_Exec_attr);

	pthread_attr_setinheritsched(&Main_Exec_attr, 1);
 	pthread_attr_setschedpolicy(&Main_Exec_attr, SCHED_FIFO);
	pthread_attr_setstacksize(&Main_Exec_attr, MAIN_STACK_SIZE);
 	Main_Exec_parm.sched_priority = MAIN_TASK_PRI;
  	pthread_attr_setschedparam(&Main_Exec_attr, &Main_Exec_parm);

	pthread_create (&Main_Exec_thread_id, &Main_Exec_attr, (void*(*)(void*))MainExecThread, 0); 

	while (true)
		pause ();

	printf ("MAIN PAUSE RETURNED\n") ;
	
}

void parent (void)
{
	while (true)
		pause ();
}

void split (void)
{
	int pid = fork ();

	if (pid == 0) // child
	{
		child ();
	}
	else // parent
	{

		Child_PID = pid;
		parent ();
	}
}
		

int main (int argc, char *argv[])
{

	Mains_Parent = getpid ();
	
#if 1
	split ();
#endif

#if 0
	child ();
#endif

}
***********************************************************************************
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***********************************************************************************

Re: [Xenomai-help] kernel oops using mq_open after fork

[Gilles Chanteperdrix]

Landau, Bracha wrote:
 > I'm using xenomai 2.2 rc3 on a MPC8247, on linux 2.6.14.
 >  
 > I have a problem using mq_open. Please see the attached code.
 > If I fork before the mq_open the kernel, I get a kernel oops.
 > 
 > Why this behaviour?

The child process has not "bound" the interface, so, it has no
per-process data. If this is the cause of the oops, the solution is to
add a pthread_atfork call in xeno_user_skin_init in order for the
process children to also call xeno_user_skin_init.

-- 


					    Gilles Chanteperdrix.

Re: [Xenomai-help] kernel oops using mq_open after fork

[Philippe Gerum]

On Wed, 2006-07-19 at 13:51 +0200, Gilles Chanteperdrix wrote:
> Landau, Bracha wrote:
>  > I'm using xenomai 2.2 rc3 on a MPC8247, on linux 2.6.14.
>  >  
>  > I have a problem using mq_open. Please see the attached code.
>  > If I fork before the mq_open the kernel, I get a kernel oops.
>  > 
>  > Why this behaviour?
> 
> The child process has not "bound" the interface, so, it has no
> per-process data. If this is the cause of the oops, the solution is to
> add a pthread_atfork call in xeno_user_skin_init in order for the
> process children to also call xeno_user_skin_init.

Additionally, don't fiddle with SIGCHLD: we use it internally.

> 
-- 
Philippe.

Re: [Xenomai-help] kernel oops using mq_open after fork

[Gilles Chanteperdrix]

[-- Attachment #1: message body and .signature --]
[-- Type: text/plain, Size: 897 bytes --]

Gilles Chanteperdrix wrote:
 > Landau, Bracha wrote:
 >  > I'm using xenomai 2.2 rc3 on a MPC8247, on linux 2.6.14.
 >  >  
 >  > I have a problem using mq_open. Please see the attached code.
 >  > If I fork before the mq_open the kernel, I get a kernel oops.
 >  > 
 >  > Why this behaviour?
 > 
 > The child process has not "bound" the interface, so, it has no
 > per-process data. If this is the cause of the oops, the solution is to
 > add a pthread_atfork call in xeno_user_skin_init in order for the
 > process children to also call xeno_user_skin_init.

Actually, this issue is specific to skins using the per-process data
feature, i.e. only the posix skin now. So, here is a fix that only fixes
the posix skin initialization. If it solve your issue I will commit it.
You only have to rebuild the user-space support, kernel-space support is
unchanged.

-- 


					    Gilles Chanteperdrix.

[-- Attachment #2: xeno-posix-fork-handler.diff --]
[-- Type: text/plain, Size: 5285 bytes --]

Index: src/skins/posix/init.c
===================================================================
--- src/skins/posix/init.c	(revision 1357)
+++ src/skins/posix/init.c	(working copy)
@@ -30,6 +30,7 @@
 int __pse51_muxid = -1;
 int __rtdm_muxid = -1;
 int __rtdm_fd_start = INT_MAX;
+static int fork_handler_registered;
 
 int __wrap_pthread_setschedparam(pthread_t, int, const struct sched_param *);
 
@@ -58,9 +59,9 @@
 	}
 
 	parm.sched_priority = 0;
-	if ((err =
-	     __wrap_pthread_setschedparam(pthread_self(), SCHED_OTHER,
-					  &parm))) {
+	err = __wrap_pthread_setschedparam(pthread_self(), SCHED_OTHER,
+					   &parm);
+	if (err) {
 		fprintf(stderr, "Xenomai Posix skin init: "
 			"pthread_setschedparam: %s\n", strerror(err));
 		exit(EXIT_FAILURE);
@@ -70,4 +71,14 @@
 		perror("Xenomai Posix skin init: munlockall");
 		exit(EXIT_FAILURE);
 	}
+
+	if (!fork_handler_registered) {
+		err = pthread_atfork(NULL, NULL, &__init_posix_interface);
+		if (err) {
+			fprintf(stderr, "Xenomai Posix skin init: "
+				"pthread_atfork: %s\n", strerror(err));
+			exit(EXIT_FAILURE);
+		}
+		fork_handler_registered = 1;
+	}
 }
Index: src/testsuite/switchtest/Makefile.am
===================================================================
--- src/testsuite/switchtest/Makefile.am	(revision 1357)
+++ src/testsuite/switchtest/Makefile.am	(working copy)
@@ -9,8 +9,7 @@
 switch_LDFLAGS =  $(XENO_POSIX_WRAPPERS) $(XENO_USER_LDFLAGS)
 
 switch_LDADD = \
-	-lpthread -lrt \
-	../../skins/posix/.libs/libpthread_rt.a
+	../../skins/posix/.libs/libpthread_rt.a	-lpthread -lrt
 
 install-data-local:
 	$(mkinstalldirs) $(DESTDIR)$(testdir)
Index: src/testsuite/switchtest/Makefile.in
===================================================================
--- src/testsuite/switchtest/Makefile.in	(revision 1357)
+++ src/testsuite/switchtest/Makefile.in	(working copy)
@@ -1,4 +1,4 @@
-# Makefile.in generated by automake 1.9.6 from Makefile.am.
+# Makefile.in generated by automake 1.9.5 from Makefile.am.
 # @configure_input@
 
 # Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
@@ -14,6 +14,8 @@
 
 @SET_MAKE@
 
+SOURCES = $(switch_SOURCES)
+
 srcdir = @srcdir@
 top_srcdir = @top_srcdir@
 VPATH = @srcdir@
@@ -229,8 +231,7 @@
 switch_CPPFLAGS = -I$(top_srcdir)/include/posix $(XENO_USER_CFLAGS) -g -I$(top_srcdir)/include
 switch_LDFLAGS = $(XENO_POSIX_WRAPPERS) $(XENO_USER_LDFLAGS)
 switch_LDADD = \
-	-lpthread -lrt \
-	../../skins/posix/.libs/libpthread_rt.a
+	../../skins/posix/.libs/libpthread_rt.a	-lpthread -lrt
 
 EXTRA_DIST = runinfo
 all: all-am
Index: src/testsuite/cyclic/Makefile.am
===================================================================
--- src/testsuite/cyclic/Makefile.am	(revision 1357)
+++ src/testsuite/cyclic/Makefile.am	(working copy)
@@ -9,8 +9,7 @@
 cyclictest_LDFLAGS = $(XENO_POSIX_WRAPPERS) $(XENO_USER_LDFLAGS)
 
 cyclictest_LDADD = \
-	-lpthread -lrt \
-	../../skins/posix/.libs/libpthread_rt.a
+	../../skins/posix/.libs/libpthread_rt.a -lpthread -lrt
 
 install-data-local:
 	$(mkinstalldirs) $(DESTDIR)$(testdir)
Index: src/testsuite/cyclic/Makefile.in
===================================================================
--- src/testsuite/cyclic/Makefile.in	(revision 1357)
+++ src/testsuite/cyclic/Makefile.in	(working copy)
@@ -1,4 +1,4 @@
-# Makefile.in generated by automake 1.9.6 from Makefile.am.
+# Makefile.in generated by automake 1.9.5 from Makefile.am.
 # @configure_input@
 
 # Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
@@ -14,6 +14,8 @@
 
 @SET_MAKE@
 
+SOURCES = $(cyclictest_SOURCES)
+
 srcdir = @srcdir@
 top_srcdir = @top_srcdir@
 VPATH = @srcdir@
@@ -229,8 +231,7 @@
 cyclictest_CPPFLAGS = -I$(top_srcdir)/include/posix $(XENO_USER_CFLAGS) -DIPIPE_TRACE=1 -I$(top_srcdir)/include
 cyclictest_LDFLAGS = $(XENO_POSIX_WRAPPERS) $(XENO_USER_LDFLAGS)
 cyclictest_LDADD = \
-	-lpthread -lrt \
-	../../skins/posix/.libs/libpthread_rt.a
+	../../skins/posix/.libs/libpthread_rt.a -lpthread -lrt
 
 EXTRA_DIST = runinfo
 all: all-am
Index: src/testsuite/irqbench/Makefile.am
===================================================================
--- src/testsuite/irqbench/Makefile.am	(revision 1357)
+++ src/testsuite/irqbench/Makefile.am	(working copy)
@@ -19,8 +19,7 @@
 	$(XENO_USER_LDFLAGS)
 
 irqloop_LDADD = \
-	-lpthread \
-	../../skins/posix/.libs/libpthread_rt.a
+	../../skins/posix/.libs/libpthread_rt.a -lpthread
 
 
 irqbench_SOURCES = irqbench.c
Index: src/testsuite/irqbench/Makefile.in
===================================================================
--- src/testsuite/irqbench/Makefile.in	(revision 1357)
+++ src/testsuite/irqbench/Makefile.in	(working copy)
@@ -1,4 +1,4 @@
-# Makefile.in generated by automake 1.9.6 from Makefile.am.
+# Makefile.in generated by automake 1.9.5 from Makefile.am.
 # @configure_input@
 
 # Copyright (C) 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002,
@@ -14,6 +14,8 @@
 
 @SET_MAKE@
 
+SOURCES = $(irqbench_SOURCES) $(irqloop_SOURCES)
+
 srcdir = @srcdir@
 top_srcdir = @top_srcdir@
 VPATH = @srcdir@
@@ -241,8 +243,7 @@
 	$(XENO_USER_LDFLAGS)
 
 irqloop_LDADD = \
-	-lpthread \
-	../../skins/posix/.libs/libpthread_rt.a
+	../../skins/posix/.libs/libpthread_rt.a -lpthread
 
 irqbench_SOURCES = irqbench.c
 irqbench_CPPFLAGS = \