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Date: Mon, 18 Nov 2013 14:26:04 +0100
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai] [Xenomai-git] Jan Kiszka : switchtest: Account for
 invalid last_switch.from field
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On 11/18/2013 01:41 PM, git repository hosting wrote:
> Module: xenomai-jki
> Branch: for-forge
> Commit: 3e6d8ff9a99262e78655329dc043aacc607eb158
> URL:    http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=3e6d8ff9a99262e78655329dc043aacc607eb158
>
> Author: Jan Kiszka <jan.kiszka@siemens.com>
> Date:   Mon Nov 18 13:19:34 2013 +0100
>
> switchtest: Account for invalid last_switch.from field
>
> If we close a test device early, no switch may have yet taken place when
> the first call to rtswitch_to_rt/nrt happens. This can cause to_idx to
> become -1, and the system will crash. Handle this corner case
> gracefully.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>
> ---
>
>   kernel/drivers/testing/switchtest.c |   10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/drivers/testing/switchtest.c b/kernel/drivers/testing/switchtest.c
> index 6f77ee9..7d17c5f 100644
> --- a/kernel/drivers/testing/switchtest.c
> +++ b/kernel/drivers/testing/switchtest.c
> @@ -147,8 +147,11 @@ static int rtswitch_to_rt(rtswitch_context_t *ctx,
>
>   	/* to == from is a special case which means
>   	   "return to the previous task". */
> -	if (to_idx == from_idx)
> +	if (to_idx == from_idx) {
>   		to_idx = ctx->error.last_switch.from;
> +		if (to_idx == -1)
> +			return -EINVAL;
> +	}

I do not see how we can reach rtswitch_to_rt without having switched 
context, since the first task to run is not an rt task.

-- 
					    Gilles.