linux-kernel - Re: [PATCH] rtc: hid-sensor-time: Add missing spin_lock

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Date:	Thu, 17 Jan 2013 13:58:55 +0100
From:	Alexander Holler <holler@...oftware.de>
To:	Thiago Farina <tfransosi@...il.com>
CC:	Axel Lin <axel.lin@...ics.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: hid-sensor-time: Add missing spin_lock_init

Am 17.01.2013 02:58, schrieb Thiago Farina:
> On Wed, Jan 16, 2013 at 11:49 PM, Axel Lin <axel.lin@...ics.com> wrote:
>> Signed-off-by: Axel Lin <axel.lin@...ics.com>
>> ---
>>   drivers/rtc/rtc-hid-sensor-time.c |    1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/rtc/rtc-hid-sensor-time.c b/drivers/rtc/rtc-hid-sensor-time.c
>> index 0438c9e..31c5728 100644
>> --- a/drivers/rtc/rtc-hid-sensor-time.c
>> +++ b/drivers/rtc/rtc-hid-sensor-time.c
>> @@ -225,6 +225,7 @@ static int hid_time_probe(struct platform_device *pdev)
>>
>>          platform_set_drvdata(pdev, time_state);
>>
>> +       spin_lock_init(&time_state->lock_last_time);
> Can you explain in the commit message why it is missing?
>
> For people not familiar with this code that isn't obvious.
>

Every spinlock must be initialized once (to SPIN_LOCK_UNLOCKED or by 
using spin_lock_init()). On most architectures SPIN_LOCK_UNLOCKED is 
just zero, therefor  the kzalloc of the time_state does it (which likely 
is the case why I haven't spotted any error without the initialization), 
but that doesn't isn't true for all architectures.

Regards,

Alexander

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