[Ocfs2-devel] [PATCH] ocfs2/dlm: fix a dead lock
Wengang Wang
wen.gang.wang at oracle.com
Mon Jul 19 19:31:18 PDT 2010
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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