[Devel] [PATCH rh7] block/ploop: Add resched points in ploop thread.
Maxim Patlasov
mpatlasov at virtuozzo.com
Tue Jun 6 02:03:35 MSK 2017
Acked-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
On 06/05/2017 05:45 AM, Konstantin Khorenko wrote:
> Maxim, please review the patch.
>
> --
> Best regards,
>
> Konstantin Khorenko,
> Virtuozzo Linux Kernel Team
>
> On 05/29/2017 12:32 PM, Andrey Ryabinin wrote:
>> Ploop thread may not reschedule for a long time and cause softlockup
>> warnings on a debug kernel:
>>
>> NMI watchdog: BUG: soft lockup - CPU#4 stuck for 22s!
>> [ploop56082:13917]
>> ...
>> RIP: 0010:[<ffffffff8256f426>] [<ffffffff8256f426>]
>> _raw_spin_unlock_irqrestore+0x46/0xc0
>> ...
>> Call Trace:
>> [<ffffffff816194f7>] __slab_free+0x207/0x2f0
>> [<ffffffff81619ff1>] kmem_cache_free+0x2d1/0x380
>> [<ffffffff81514412>] mempool_free_slab+0x22/0x30
>> [<ffffffff815159ae>] mempool_free+0x14e/0x1f0
>> [<ffffffff81747d6a>] bio_put+0x17a/0x270
>> [<ffffffff81735837>] end_bio_bh_io_sync+0xc7/0x120
>> [<ffffffff81747d6a>] bio_put+0x17a/0x270
>> [<ffffffff81735837>] end_bio_bh_io_sync+0xc7/0x120
>> [<ffffffff8174a5ac>] bio_endio+0x13c/0x220
>> [<ffffffffa0858a38>] ploop_complete_request+0x148/0x1c60 [ploop]
>> [<ffffffffa086b06d>] ploop_req_state_process+0x1f7d/0x3870 [ploop]
>> [<ffffffffa086cfce>] ploop_thread+0x66e/0x1170 [ploop]
>> [<ffffffff8121dcb6>] kthread+0x1e6/0x250
>> [<ffffffff8258ae58>] ret_from_fork+0x58/0x90
>>
>> Add cond_resched() on each iteration of the ploop_thread() to fix that.
>>
>> https://jira.sw.ru/browse/PSBM-66617
>> Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
>> ---
>> drivers/block/ploop/dev.c | 22 ++++++++++------------
>> drivers/block/ploop/discard.c | 2 +-
>> include/linux/ploop/ploop.h | 3 +--
>> 3 files changed, 12 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
>> index e7aec54172c0..eab6cb067708 100644
>> --- a/drivers/block/ploop/dev.c
>> +++ b/drivers/block/ploop/dev.c
>> @@ -230,8 +230,7 @@ static void ploop_test_and_clear_blockable(struct
>> ploop_device *plo,
>> }
>>
>> /* always called with plo->lock released */
>> -void ploop_preq_drop(struct ploop_device * plo, struct list_head
>> *drop_list,
>> - int keep_locked)
>> +void ploop_preq_drop(struct ploop_device * plo, struct list_head
>> *drop_list)
>> {
>> struct ploop_request * preq;
>> int drop_qlen = 0;
>> @@ -261,8 +260,7 @@ void ploop_preq_drop(struct ploop_device * plo,
>> struct list_head *drop_list,
>>
>> ploop_uncongest(plo);
>>
>> - if (!keep_locked)
>> - spin_unlock_irq(&plo->lock);
>> + spin_unlock_irq(&plo->lock);
>> }
>>
>> static void merge_rw_flags_to_req(unsigned long rw,
>> @@ -1066,7 +1064,7 @@ out:
>> blk_check_plugged(ploop_unplug, plo, sizeof(struct blk_plug_cb));
>>
>> if (!list_empty(&drop_list))
>> - ploop_preq_drop(plo, &drop_list, 0);
>> + ploop_preq_drop(plo, &drop_list);
>>
>> return;
>> }
>> @@ -2964,12 +2962,12 @@ static int ploop_thread(void * data)
>> set_user_nice(current, -20);
>>
>> blk_start_plug(&plug);
>> - spin_lock_irq(&plo->lock);
>> for (;;) {
>> /* Convert bios to preqs early (at least before processing
>> * entry queue) to increase chances of bio merge
>> */
>> - again:
>> + cond_resched();
>> + spin_lock_irq(&plo->lock);
>> BUG_ON (!list_empty(&drop_list));
>>
>> process_pending_bios(plo, &drop_list);
>> @@ -2978,8 +2976,8 @@ static int ploop_thread(void * data)
>>
>> if (!list_empty(&drop_list)) {
>> spin_unlock_irq(&plo->lock);
>> - ploop_preq_drop(plo, &drop_list, 1);
>> - goto again;
>> + ploop_preq_drop(plo, &drop_list);
>> + continue;
>> }
>>
>> if (!list_empty(&plo->ready_queue)) {
>> @@ -2991,7 +2989,6 @@ static int ploop_thread(void * data)
>>
>> ploop_req_state_process(preq);
>>
>> - spin_lock_irq(&plo->lock);
>> continue;
>> }
>>
>> @@ -3010,6 +3007,7 @@ static int ploop_thread(void * data)
>> set_bit(PLOOP_S_ATTENTION, &plo->state);
>> if (plo->active_reqs) {
>> list_add(&preq->list, &plo->entry_queue);
>> + spin_unlock_irq(&plo->lock);
>> continue;
>> }
>> plo->barrier_reqs--;
>> @@ -3042,8 +3040,6 @@ static int ploop_thread(void * data)
>> spin_unlock_irq(&plo->lock);
>>
>> ploop_req_state_process(preq);
>> -
>> - spin_lock_irq(&plo->lock);
>> continue;
>> }
>>
>> @@ -3058,8 +3054,10 @@ static int ploop_thread(void * data)
>>
>> wait_more:
>> ploop_wait(plo, once, &plug);
>> + spin_unlock_irq(&plo->lock);
>> once = 0;
>> }
>> +
>> spin_unlock_irq(&plo->lock);
>> blk_finish_plug(&plug);
>>
>> diff --git a/drivers/block/ploop/discard.c
>> b/drivers/block/ploop/discard.c
>> index 828ab3696469..33122497b9c5 100644
>> --- a/drivers/block/ploop/discard.c
>> +++ b/drivers/block/ploop/discard.c
>> @@ -66,7 +66,7 @@ int ploop_discard_fini_ioc(struct ploop_device *plo)
>> spin_unlock_irq(&plo->lock);
>>
>> if (!list_empty(&drop_list))
>> - ploop_preq_drop(plo, &drop_list, 0);
>> + ploop_preq_drop(plo, &drop_list);
>>
>> if (plo->maintenance_type != PLOOP_MNTN_DISCARD) {
>> ret = -EBUSY;
>> diff --git a/include/linux/ploop/ploop.h b/include/linux/ploop/ploop.h
>> index c7261c4bda57..f13b7caa4128 100644
>> --- a/include/linux/ploop/ploop.h
>> +++ b/include/linux/ploop/ploop.h
>> @@ -633,8 +633,7 @@ static inline struct ploop_delta *
>> map_top_delta(struct ploop_map * map)
>>
>> void ploop_complete_io_state(struct ploop_request * preq);
>> void ploop_fail_request(struct ploop_request * preq, int err);
>> -void ploop_preq_drop(struct ploop_device * plo, struct list_head
>> *drop_list,
>> - int keep_locked);
>> +void ploop_preq_drop(struct ploop_device * plo, struct list_head
>> *drop_list);
>>
>>
>> static inline int ploop_req_delay_fua_possible(struct ploop_request
>> *preq)
>>
More information about the Devel
mailing list