[Ocfs2-devel] [PATCH 1/1] ocfs2: use spinlock irqsave for downconvert lock.patch
srinivas eeda
srinivas.eeda at oracle.com
Sun Jan 29 15:44:24 PST 2012
Hi Tao,
thanks for reviewing.
>> 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?
When ocfs2dc thread is running on a cpu and acquired dc_task_lock spin
lock, an interrupt came in for i/o completion. Interrupt handler then
tries to acquire same spinlock and ends up in deadlock. Below is the
stack that gives more details.
[<ffffffff814fd509>] default_do_nmi+0x39/0x200
[<ffffffff814fd750>] do_nmi+0x80/0xa0
[<ffffffff814fced0>] nmi+0x20/0x30
[<ffffffff8103ee83>] ? __ticket_spin_lock+0x13/0x20
<<EOE>> <IRQ> [<ffffffff814fc41e>] _raw_spin_lock+0xe/0x20
[<ffffffffa04e32e8>] ocfs2_wake_downconvert_thread+0x28/0x60 [ocfs2]
[<ffffffffa04eb388>] ocfs2_rw_unlock+0xe8/0x1a0 [ocfs2]
[<ffffffff8110c635>] ? mempool_free+0x95/0xa0
[<ffffffffa04d18c1>] ocfs2_dio_end_io+0x61/0xb0 [ocfs2]
[<ffffffff8119ebdb>] dio_complete+0xbb/0xe0
[<ffffffff8119ec6d>] dio_bio_end_aio+0x6d/0xc0
[<ffffffff8119a1bd>] bio_endio+0x1d/0x40
[<ffffffff81234643>] req_bio_endio+0xa3/0xe0
[<ffffffff8123589f>] blk_update_request+0xff/0x490
[<ffffffff8119bec4>] ? bio_free+0x64/0x70
[<ffffffffa000193a>] end_clone_bio+0x5a/0x90 [dm_mod]
[<ffffffff8119a1bd>] bio_endio+0x1d/0x40
[<ffffffff81234643>] req_bio_endio+0xa3/0xe0
[<ffffffff813558a6>] ? scsi_done+0x26/0x60
[<ffffffff8123589f>] blk_update_request+0xff/0x490
[<ffffffffa01ee77a>] ? qla2x00_process_completed_request+0x5a/0xe0 [qla2xxx]
[<ffffffff81235c57>] blk_update_bidi_request+0x27/0xb0
[<ffffffff81236d8f>] blk_end_bidi_request+0x2f/0x80
[<ffffffff81236e30>] blk_end_request+0x10/0x20
[<ffffffff8135d600>] scsi_end_request+0x40/0xb0
[<ffffffff8135d96f>] scsi_io_completion+0x9f/0x5c0
[<ffffffff8103ef19>] ? default_spin_lock_flags+0x9/0x10
[<ffffffff81354a59>] scsi_finish_command+0xc9/0x130
[<ffffffff8135dff7>] scsi_softirq_done+0x147/0x170
[<ffffffff8123ca32>] blk_done_softirq+0x82/0xa0
[<ffffffff8106f987>] __do_softirq+0xb7/0x210
[<ffffffff814fc41e>] ? _raw_spin_lock+0xe/0x20
[<ffffffff8150599c>] call_softirq+0x1c/0x30
[<ffffffff81016365>] do_softirq+0x65/0xa0
[<ffffffff8106f78d>] irq_exit+0xbd/0xe0
[<ffffffff815061f6>] do_IRQ+0x66/0xe0
@ [<ffffffff814fc953>] common_interrupt+0x13/0x13
<EOI> [<ffffffff81261625>] ? __list_del_entry+0x35/0xd0
[<ffffffffa04e9d53>] ocfs2_downconvert_thread+0x133/0x2a0 [ocfs2]
[<ffffffff814f9d10>] ? __schedule+0x3f0/0x800
[<ffffffff8108b930>] ? wake_up_bit+0x40/0x40
[<ffffffffa04e9c20>] ? ocfs2_process_blocked_lock+0x270/0x270 [ocfs2]
[<ffffffff8108b346>] kthread+0x96/0xa0
[<ffffffff815058a4>] kernel_thread_helper+0x4/0x10
[<ffffffff8108b2b0>] ? kthread_worker_fn+0x1a0/0x1a0
[<ffffffff815058a0>] ? gs_change+0x13/0x13
@ ---[ end trace 628bf423ee0bc8a8 ]---
> btw, if you are afraid of deadlocking in soft IRQ, I guess we should use
> spin_lock_bh not spin_lock_irqsave?
Yes, looks like we could, but I am not 100% sure if it will be safe?
> 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);
>> }
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