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From: Philippe Gerum <rpm@xenomai.org>
Message-ID: <56969AF7.6040505@xenomai.org>
Date: Wed, 13 Jan 2016 19:44:07 +0100
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Subject: Re: [Xenomai] [Xenomai-git] Jan Kiszka : cobalt/kernel: Fix
 invalidation of cond shadow
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To: "Kiszka, Jan" <jan.kiszka@siemens.com>
Cc: xenomai@xenomai.org

On 01/13/2016 07:33 PM, git repository hosting wrote:
> Module: xenomai-jki
> Branch: for-forge
> Commit: b7d37dab571df0c0cd42aae094c3d5d1bc71db80
> URL:    http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=b7d37dab571df0c0cd42aae094c3d5d1bc71db80
> 
> Author: Jan Kiszka <jan.kiszka@siemens.com>
> Date:   Wed Jan 13 19:31:23 2016 +0100
> 
> cobalt/kernel: Fix invalidation of cond shadow
> 
> pthread_cond_destroy fails to invalidate also the shadow object. This
> can cause spurious -EBUSY errors on re-initialization of the very same
> shadow as condition variable later on.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> 
> ---
> 
>  kernel/cobalt/posix/cond.c |    2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/cobalt/posix/cond.c b/kernel/cobalt/posix/cond.c
> index 7e115cf..84ae8fd 100644
> --- a/kernel/cobalt/posix/cond.c
> +++ b/kernel/cobalt/posix/cond.c
> @@ -117,6 +117,8 @@ static inline int pthread_cond_destroy(struct cobalt_cond_shadow *cnd)
>  
>  	cobalt_cond_reclaim(&cond->resnode, s); /* drops lock */
>  
> +	cobalt_mark_deleted(cnd);
> +
>  	return 0;
>  }
>  
>

cobalt_cond_reclaim() invalidates the shadow object already. Did you
observe -EBUSY already? If so, maybe a rescheduling happens early when
flushing the synchro object, before the invalidation takes place in that
routine.

i.e.

diff --git a/kernel/cobalt/posix/cond.c b/kernel/cobalt/posix/cond.c
index 7e115cf..3f81b47 100644
--- a/kernel/cobalt/posix/cond.c
+++ b/kernel/cobalt/posix/cond.c
@@ -414,8 +414,8 @@ void cobalt_cond_reclaim(struct cobalt_resnode
*node, spl_t s)
 	cond = container_of(node, struct cobalt_cond, resnode);
 	xnregistry_remove(node->handle);
 	cobalt_del_resource(node);
-	xnsynch_destroy(&cond->synchbase);
 	cobalt_mark_deleted(cond);
+	xnsynch_destroy(&cond->synchbase);
 	xnlock_put_irqrestore(&nklock, s);

 	cobalt_umm_free(&cobalt_ppd_get(cond->attr.pshared)->umm,

-- 
Philippe.