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.e...@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);
> }
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