[Ocfs2-devel] [PATCH] ocfs2/dlm: fix a dead lock

[Sunil Mushran]

Acked-by: Sunil Mushran <sunil.mushran at oracle.com>

On 07/19/2010 07:31 PM, Wengang Wang wrote:
> Just a reminder.
>
> wengang.
> On 10-07-16 23:13, Wengang Wang wrote:
>    
>> When we have to take both dlm->master_lock and lockres->spinlock,
>> take them in order
>>
>> lockres->spinlock and then dlm->master_lock.
>>
>> The patch fixes a violation of the rule.
>> We can simply move taking dlm->master_lock to where we have dropped res->spinlock
>> since when we access res->state and free mle memory we don't need master_lock's
>> protection.
>>
>> Signed-off-by: Wengang Wang<wen.gang.wang at oracle.com>
>> ---
>>   fs/ocfs2/dlm/dlmmaster.c |    5 ++---
>>   1 files changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
>> index 94b97fc..6d098b8 100644
>> --- a/fs/ocfs2/dlm/dlmmaster.c
>> +++ b/fs/ocfs2/dlm/dlmmaster.c
>> @@ -3050,8 +3050,6 @@ int dlm_migrate_request_handler(struct o2net_msg *msg, u32 len, void *data,
>>   	/* check for pre-existing lock */
>>   	spin_lock(&dlm->spinlock);
>>   	res = __dlm_lookup_lockres(dlm, name, namelen, hash);
>> -	spin_lock(&dlm->master_lock);
>> -
>>   	if (res) {
>>   		spin_lock(&res->spinlock);
>>   		if (res->state&  DLM_LOCK_RES_RECOVERING) {
>> @@ -3069,14 +3067,15 @@ int dlm_migrate_request_handler(struct o2net_msg *msg, u32 len, void *data,
>>   		spin_unlock(&res->spinlock);
>>   	}
>>
>> +	spin_lock(&dlm->master_lock);
>>   	/* ignore status.  only nonzero status would BUG. */
>>   	ret = dlm_add_migration_mle(dlm, res, mle,&oldmle,
>>   				    name, namelen,
>>   				    migrate->new_master,
>>   				    migrate->master);
>>
>> -unlock:
>>   	spin_unlock(&dlm->master_lock);
>> +unlock:
>>   	spin_unlock(&dlm->spinlock);
>>
>>   	if (oldmle) {
>> -- 
>> 1.6.6.1
>>
>>
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>>      
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