[Xenomai-core] Linux lock-up with rtcanrecv

[Jan Kiszka <jan.kiszka@domain.hid>]

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Hi all,

fiddling with latest Xenomai trunk and 2.3.x on one of our robots (there
is still a bug in trunk /wrt broken timeouts of rt_dev_read on
xeno_16550A - different issue...), I ran into a weird behaviour of
rtcanrecv:

I have a continuous stream of a few thousand packets/s towards the
robot. When I start up two "rtcanrecv rtcan0 -p1000" instances (or one +
our own receiver application), the second one causes a Linux lock-up.
Sometimes this happens during startup of the second rtcanrecv, but at
latest on its termination. Other RT tasks are still running. I can
resolve the lock-up by pulling the CAN cable, everyone is fine
afterwards and can be cleaned up. I played with quite a few combinations
of recent ipipe patches and Xenomai revisions (even back to #1084 in
v2.3.x), no noticeable difference.

Seems like I have to take a closer look - once time permits and the
robot is available. So any ideas or attempts to reproduce this are
welcome, current .config attached (no magic knob found there yet).

Jan


PS: Wolfgang, any objections against "decoupling" -v from -p and
lowering the receiver priority to 0?

Index: src/utils/can/rtcanrecv.c
===================================================================
--- src/utils/can/rtcanrecv.c	(revision 2146)
+++ src/utils/can/rtcanrecv.c	(working copy)
@@ -192,6 +192,7 @@ int main(int argc, char **argv)

 	case 'p':
 	    print = strtoul(optarg, NULL, 0);
+	    break;

 	case 'v':
 	    verbose = 1;
@@ -312,7 +313,7 @@ int main(int argc, char **argv)
     }

     snprintf(name, sizeof(name), "rtcanrecv-%d", getpid());
-    ret = rt_task_shadow(&rt_task_desc, name, 1, 0);
+    ret = rt_task_shadow(&rt_task_desc, name, 0, 0);
     if (ret) {
 	fprintf(stderr, "rt_task_shadow: %s\n", strerror(-ret));
 	goto failure;


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