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.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); >> } _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com http://oss.oracle.com/mailman/listinfo/ocfs2-devel