lkml.org 
[lkml]   [2015]   [Oct]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCHv2 1/1] SCSI: update hosts module to use idr index management
From
Date
On 10/06/2015 07:17 PM, James Bottomley wrote:
> On Tue, 2015-10-06 at 10:14 -0700, Lee Duncan wrote:
>> On 10/06/2015 02:40 AM, Christoph Hellwig wrote:
>>>> struct Scsi_Host *scsi_host_lookup(unsigned short hostnum)
>>>> {
>>>> - struct device *cdev;
>>>> - struct Scsi_Host *shost = NULL;
>>>> -
>>>> - cdev = class_find_device(&shost_class, NULL, &hostnum,
>>>> - __scsi_host_match);
>>>> - if (cdev) {
>>>> - shost = scsi_host_get(class_to_shost(cdev));
>>>> - put_device(cdev);
>>>> - }
>>>> + struct Scsi_Host *shost;
>>>> +
>>>> + spin_lock(&host_index_lock);
>>>> + shost = idr_find(&host_index_idr, hostnum);
>>>> + spin_unlock(&host_index_lock);
>>>> +
>>>> return shost;
>>>
>>> How does this actually grab a reference to the host?
>>
>> Good catch -- I should have noticed that.
>>
>> I will resubmit the patch.
>
> I'll wait to see what you produce, but I don't think, using a separate
> idr array, you can close the race window between lookup and get. One of
> the nice things about using the cdev iterator is that the get is part of
> the lookup process.
>
Hmm. Should be possible if you free up the IDR in scsi_remove_host(),
just after setting the state to SHOST_DEL.

Cheers,

Hannes



\
 
 \ /
  Last update: 2015-10-07 22:41    [W:0.062 / U:0.256 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site