[Ocfs2-devel] [PATCH 1/1] ocfs2: use spinlock irqsave for downconvert lock.patch

[Tao Ma]

Hi Srini,
On 01/29/2012 10:13 AM, Srinivas Eeda wrote:
> When ocfs2dc thread holds dc_task_lock spinlock and receives soft IRQ for
> I/O completion it deadlock itself trying to get same spinlock in
> ocfs2_wake_downconvert_thread
could you please describe it in more detail?

btw, if you are afraid of deadlocking in soft IRQ, I guess we should use
spin_lock_bh not spin_lock_irqsave?

Thanks
Tao
> 
> The patch disables interrupts when acquiring dc_task_lock spinlock
> 
> Signed-off-by: Srinivas Eeda <srinivas.eeda at oracle.com>
> ---
>  fs/ocfs2/dlmglue.c |   30 ++++++++++++++++++------------
>  1 files changed, 18 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
> index 81a4cd2..d8552a5 100644
> --- a/fs/ocfs2/dlmglue.c
> +++ b/fs/ocfs2/dlmglue.c
> @@ -3932,6 +3932,8 @@ unqueue:
>  static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
>  					struct ocfs2_lock_res *lockres)
>  {
> +	unsigned long flags;
> +
>  	assert_spin_locked(&lockres->l_lock);
>  
>  	if (lockres->l_flags & OCFS2_LOCK_FREEING) {
> @@ -3945,21 +3947,22 @@ static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
>  
>  	lockres_or_flags(lockres, OCFS2_LOCK_QUEUED);
>  
> -	spin_lock(&osb->dc_task_lock);
> +	spin_lock_irqsave(&osb->dc_task_lock, flags);
>  	if (list_empty(&lockres->l_blocked_list)) {
>  		list_add_tail(&lockres->l_blocked_list,
>  			      &osb->blocked_lock_list);
>  		osb->blocked_lock_count++;
>  	}
> -	spin_unlock(&osb->dc_task_lock);
> +	spin_unlock_irqrestore(&osb->dc_task_lock, flags);
>  }
>  
>  static void ocfs2_downconvert_thread_do_work(struct ocfs2_super *osb)
>  {
>  	unsigned long processed;
> +	unsigned long flags;
>  	struct ocfs2_lock_res *lockres;
>  
> -	spin_lock(&osb->dc_task_lock);
> +	spin_lock_irqsave(&osb->dc_task_lock, flags);
>  	/* grab this early so we know to try again if a state change and
>  	 * wake happens part-way through our work  */
>  	osb->dc_work_sequence = osb->dc_wake_sequence;
> @@ -3972,38 +3975,40 @@ static void ocfs2_downconvert_thread_do_work(struct ocfs2_super *osb)
>  				     struct ocfs2_lock_res, l_blocked_list);
>  		list_del_init(&lockres->l_blocked_list);
>  		osb->blocked_lock_count--;
> -		spin_unlock(&osb->dc_task_lock);
> +		spin_unlock_irqrestore(&osb->dc_task_lock, flags);
>  
>  		BUG_ON(!processed);
>  		processed--;
>  
>  		ocfs2_process_blocked_lock(osb, lockres);
>  
> -		spin_lock(&osb->dc_task_lock);
> +		spin_lock_irqsave(&osb->dc_task_lock, flags);
>  	}
> -	spin_unlock(&osb->dc_task_lock);
> +	spin_unlock_irqrestore(&osb->dc_task_lock, flags);
>  }
>  
>  static int ocfs2_downconvert_thread_lists_empty(struct ocfs2_super *osb)
>  {
>  	int empty = 0;
> +	unsigned long flags;
>  
> -	spin_lock(&osb->dc_task_lock);
> +	spin_lock_irqsave(&osb->dc_task_lock, flags);
>  	if (list_empty(&osb->blocked_lock_list))
>  		empty = 1;
>  
> -	spin_unlock(&osb->dc_task_lock);
> +	spin_unlock_irqrestore(&osb->dc_task_lock, flags);
>  	return empty;
>  }
>  
>  static int ocfs2_downconvert_thread_should_wake(struct ocfs2_super *osb)
>  {
>  	int should_wake = 0;
> +	unsigned long flags;
>  
> -	spin_lock(&osb->dc_task_lock);
> +	spin_lock_irqsave(&osb->dc_task_lock, flags);
>  	if (osb->dc_work_sequence != osb->dc_wake_sequence)
>  		should_wake = 1;
> -	spin_unlock(&osb->dc_task_lock);
> +	spin_unlock_irqrestore(&osb->dc_task_lock, flags);
>  
>  	return should_wake;
>  }
> @@ -4033,10 +4038,11 @@ static int ocfs2_downconvert_thread(void *arg)
>  
>  void ocfs2_wake_downconvert_thread(struct ocfs2_super *osb)
>  {
> -	spin_lock(&osb->dc_task_lock);
> +	unsigned long flags;
> +	spin_lock_irqsave(&osb->dc_task_lock, flags);
>  	/* make sure the voting thread gets a swipe at whatever changes
>  	 * the caller may have made to the voting state */
>  	osb->dc_wake_sequence++;
> -	spin_unlock(&osb->dc_task_lock);
> +	spin_unlock_irqrestore(&osb->dc_task_lock, flags);
>  	wake_up(&osb->dc_event);
>  }