linux-kernel - Re: [PATCH] ipmi_si: use smi_num for init

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Message-ID: <516358b2-28f9-c036-65ab-aa05fd5ed6b7@redhat.com>
Date:   Mon, 10 Apr 2017 13:48:23 -0400
From:   Tony Camuso <tcamuso@...hat.com>
To:     minyard@....org
Cc:     openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Corey Minyard <cminyard@...sta.com>
Subject: Re: [PATCH] ipmi_si: use smi_num for init_name

On 04/10/2017 01:43 PM, minyard@....org wrote:
> From: Tony Camuso <tcamuso@...hat.com>
>
> Commit 1abf71e moved the creation of new_smi->dev to earlier in the init
> sequence in order to provide infrastructure for log printing.
>
> However, the init_name was created with a hard-coded value of zero. This
> presents a problem in systems with more than one interface, producing a
> call trace in dmesg.
>
> To correct the problem, simply use smi_num instead of the hard-coded
> value of zero.
>
> Tested on a lenovo x3950.
>
> Signed-off-by: Tony Camuso <tcamuso@...hat.com>
>
> There was actually a more general problem, the platform device wasn't
> being set correctly, either, and there was a possible (though extremely
> unlikely) race on smi_num.  Add locks to clean up the race and use the
> proper value for the platform device, too.

Ouch! I thought smi_num was already locked by smi_infos. Now I see that
it wasn't.

Thanks!

Regards,
tony

>
> Tested on qemu in various configurations.
>
> Signed-off-by: Corey Minyard <cminyard@...sta.com>
> ---
>
> I reworked this a bit, I think I've covered all the problems with
> smi_num.  Tony, does this work for you?
>
> Thanks
>
>  drivers/char/ipmi/ipmi_si_intf.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
> index 2a7c425..b2b618f 100644
> --- a/drivers/char/ipmi/ipmi_si_intf.c
> +++ b/drivers/char/ipmi/ipmi_si_intf.c
> @@ -1954,7 +1954,9 @@ static int hotmod_handler(const char *val, struct kernel_param *kp)
>  				kfree(info);
>  				goto out;
>  			}
> +			mutex_lock(&smi_infos_lock);
>  			rv = try_smi_init(info);
> +			mutex_unlock(&smi_infos_lock);
>  			if (rv) {
>  				cleanup_one_si(info);
>  				goto out;
> @@ -2042,8 +2044,10 @@ static int hardcode_find_bmc(void)
>  		info->slave_addr = slave_addrs[i];
>
>  		if (!add_smi(info)) {
> +			mutex_lock(&smi_infos_lock);
>  			if (try_smi_init(info))
>  				cleanup_one_si(info);
> +			mutex_unlock(&smi_infos_lock);
>  			ret = 0;
>  		} else {
>  			kfree(info);
> @@ -3492,6 +3496,11 @@ static int add_smi(struct smi_info *new_smi)
>  	return rv;
>  }
>
> +/*
> + * Try to start up an interface.  Must be called with smi_infos_lock
> + * held, primarily to keep smi_num consistent, we only one to do these
> + * one at a time.
> + */
>  static int try_smi_init(struct smi_info *new_smi)
>  {
>  	int rv = 0;
> @@ -3524,9 +3533,12 @@ static int try_smi_init(struct smi_info *new_smi)
>  		goto out_err;
>  	}
>
> +	new_smi->intf_num = smi_num;
> +
>  	/* Do this early so it's available for logs. */
>  	if (!new_smi->dev) {
> -		init_name = kasprintf(GFP_KERNEL, "ipmi_si.%d", 0);
> +		init_name = kasprintf(GFP_KERNEL, "ipmi_si.%d",
> +				      new_smi->intf_num);
>
>  		/*
>  		 * If we don't already have a device from something
> @@ -3593,8 +3605,6 @@ static int try_smi_init(struct smi_info *new_smi)
>
>  	new_smi->interrupt_disabled = true;
>  	atomic_set(&new_smi->need_watch, 0);
> -	new_smi->intf_num = smi_num;
> -	smi_num++;
>
>  	rv = try_enable_event_buffer(new_smi);
>  	if (rv == 0)
> @@ -3661,6 +3671,9 @@ static int try_smi_init(struct smi_info *new_smi)
>  		goto out_err_stop_timer;
>  	}
>
> +	/* Don't increment till we know we have succeeded. */
> +	smi_num++;
> +
>  	dev_info(new_smi->dev, "IPMI %s interface initialized\n",
>  		 si_to_str[new_smi->si_type]);
>
>