Re: [Xenomai] Issue with cobalt_monitor_wait()

[Philippe Gerum <rpm@xenomai.org>]

On 07/08/2014 06:10 PM, Matthias Schneider wrote:
> ----- Original Message -----
> 
>> From: Philippe Gerum <rpm@xenomai.org>
>> To: Matthias Schneider <ma30002000@yahoo.de>; "xenomai@xenomai.org" <xenomai@xenomai.org>
>> Cc:
>> Sent: Sunday, July 6, 2014 11:15 PM
>> Subject: Re: [Xenomai] Issue with cobalt_monitor_wait()
>>
>> On 07/06/2014 10:16 PM, Matthias Schneider wrote:
>>
>> [snip]
>>
>>>   On thing I do not understand is:
>>>
>>>   in kernel cobalt_monitor_wait(), the synch object is unlocked via
>>>   xnsynch_release(). What happens if this synchobj was locked via
>>>   mon->gate.fastlock ? Shouldnt that also be released?
>>>
>>
>> xnsynch_release() handles fastlocks as well.
>>
>>
>>>   What other reason could there be if the synch object was released
>>>   via xnsynch_release, xnsynch_acquire was interrupted for
>>>   xnsynch_release to block?
>>>
>>
>> Since the issue seems to be easily reproducible, could you send a
>> self-contained piece of code illustrating it?
>>
>> Also, please mention if you are seeing this issue only when running your
>> app over GDB, or if it currently happens without any debugger attached.
>>
>> TIA,
> 
> 
> It seems I have not described the problematic scenario completely -
> 
> there were two other threads that call called syncobj_lock()
> / cobalt_monitor_enter() at about the same time. (Actually there
> are three concurrent on the queue that is being tested, two receive
> operation and one send operation). I am pretty sure that the issue is
> extremely timing dependent.
> 
> Anyway, the testcase would be
> 
> queue_test_receive_peek_multiple_tasks()
> 
> in
> 
> freertos/lib/queue-1.c
> 
> I have already submitted as a patch. In case it helps, I can
> try tro reproduce the issue with another queue implementation
> (e.g. psos) and send a short code snippet.
> 

Ok, I'll tackle this bug tomorrow. Looking at the test code, the above change would avoid issues down the road:

diff --git a/lib/freertos/testsuite/queue-1.c b/lib/freertos/testsuite/queue-1.c
index cc2087d..ed81bc1 100644
--- a/lib/freertos/testsuite/queue-1.c
+++ b/lib/freertos/testsuite/queue-1.c
@@ -20,6 +20,7 @@
 #include <stdlib.h>
 #include <dirent.h>
 #include <copperplate/traceobj.h>
+#include <copperplate/clockobj.h>
 #include <boilerplate/time.h>
 
 #include <freertos/FreeRTOS.h>
@@ -27,13 +28,6 @@
 #include <freertos/queue.h>
 #include <freertos/semphr.h>
 
-#include <xeno_config.h>
-#ifdef CONFIG_XENO_RAW_CLOCK_ENABLED
-#define CLOCK_COPPERPLATE  CLOCK_MONOTONIC_RAW
-#else
-#define CLOCK_COPPERPLATE  CLOCK_MONOTONIC
-#endif
-
 #include "test_task.h"
 
 static struct traceobj trobj;

-- 
Philippe.