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

[Wengang Wang <wen.gang.wang@oracle.com>]

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@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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