From mboxrd@z Thu Jan  1 00:00:00 1970
From: Juergen Gross <jgross@suse.com>
Subject: Re: [PATCH Linux-2.6.18] scsifront: avoid aquiring same
 lock twice if ring is full
Date: Wed, 14 Jan 2015 05:27:12 +0100
Message-ID: <54B5F020.3080903@suse.com>
References: <1421166178-626-1-git-send-email-jgross@suse.com>
	<20150113185358.GE5962@reaktio.net>
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To: =?windows-1252?Q?Pasi_K=E4rkk=E4inen?= <pasik@iki.fi>
Cc: jbeulich@suse.com, xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

On 01/13/2015 07:53 PM, Pasi K=E4rkk=E4inen wrote:
> Hi,
>
> On Tue, Jan 13, 2015 at 05:22:58PM +0100, Juergen Gross wrote:
>> The locking in scsifront_dev_reset_handler() is obviously wrong. In
>> case of a full ring the host lock is aquired twice.
>>
>> Fixing this issue enables to get rid of the endless fo loop with an
>> explicit break statement.
>>
>
> Is this patch needed in upstream Linux kernel aswell, now that Xen PVSCSI=
 drivers are in upstream Linux ?

No, especially this part of the code was reorganized and doesn't
have that issue.

Juergen

>
>
> Thanks,
>
> -- Pasi
>
>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>>
>> diff -r 078f1bb69ea5 drivers/xen/scsifront/scsifront.c
>> --- a/drivers/xen/scsifront/scsifront.c	Wed Dec 10 10:22:39 2014 +0100
>> +++ b/drivers/xen/scsifront/scsifront.c	Tue Jan 13 14:32:33 2015 +0100
>> @@ -447,12 +447,10 @@ static int scsifront_dev_reset_handler(s
>>   	uint16_t rqid;
>>   	int err =3D 0;
>>
>> -	for (;;) {
>>   #if LINUX_VERSION_CODE >=3D KERNEL_VERSION(2,6,12)
>> -		spin_lock_irq(host->host_lock);
>> +	spin_lock_irq(host->host_lock);
>>   #endif
>> -		if (!RING_FULL(&info->ring))
>> -			break;
>> +	while (RING_FULL(&info->ring)) {
>>   		if (err) {
>>   #if LINUX_VERSION_CODE >=3D KERNEL_VERSION(2,6,12)
>>   			spin_unlock_irq(host->host_lock);
>>
>> _______________________________________________
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>