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Date: Wed, 17 Mar 2021 10:45:14 +0800
From: Can Guo <cang@...eaurora.org>
To: Avri Altman <Avri.Altman@....com>
Cc: "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
"Martin K . Petersen" <martin.petersen@...cle.com>,
linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
gregkh@...uxfoundation.org, Bart Van Assche <bvanassche@....org>,
yongmyung lee <ymhungry.lee@...sung.com>,
Daejun Park <daejun7.park@...sung.com>,
alim.akhtar@...sung.com, asutoshd@...eaurora.org,
Zang Leigang <zangleigang@...ilicon.com>,
Avi Shchislowski <Avi.Shchislowski@....com>,
Bean Huo <beanhuo@...ron.com>, stanley.chu@...iatek.com
Subject: Re: [PATCH v5 07/10] scsi: ufshpb: Add "Cold" regions timer
On 2021-03-16 17:21, Avri Altman wrote:
>> > +static void ufshpb_read_to_handler(struct work_struct *work)
>> > +{
>> > + struct delayed_work *dwork = to_delayed_work(work);
>> > + struct ufshpb_lu *hpb;
>> > + struct victim_select_info *lru_info;
>> > + struct ufshpb_region *rgn;
>> > + unsigned long flags;
>> > + LIST_HEAD(expired_list);
>> > +
>> > + hpb = container_of(dwork, struct ufshpb_lu, ufshpb_read_to_work);
>> > +
>> > + spin_lock_irqsave(&hpb->rgn_state_lock, flags);
>> > +
>> > + lru_info = &hpb->lru_info;
>> > +
>> > + list_for_each_entry(rgn, &lru_info->lh_lru_rgn, list_lru_rgn) {
>> > + bool timedout = ktime_after(ktime_get(), rgn->read_timeout);
>> > +
>> > + if (timedout) {
>> > + rgn->read_timeout_expiries--;
>> > + if (is_rgn_dirty(rgn) ||
>> > + rgn->read_timeout_expiries == 0)
>> > + list_add(&rgn->list_expired_rgn, &expired_list);
>> > + else
>> > + rgn->read_timeout = ktime_add_ms(ktime_get(),
>> > + READ_TO_MS);
>> > + }
>> > + }
>> > +
>> > + spin_unlock_irqrestore(&hpb->rgn_state_lock, flags);
>> > +
>> > + list_for_each_entry(rgn, &expired_list, list_expired_rgn) {
>>
>> Here can be problematic - since you don't have the native expired_list
>> initialized
>> before use, if above loop did not insert anything to expired_list, it
>> shall become
>> a dead loop here.
> Not sure what you meant by native initialization.
> LIST_HEAD is statically initializing an empty list, resulting the same
> outcome as INIT_LIST_HEAD.
>
Sorry for making you confused, you should use list_for_each_entry_safe()
instead of list_for_each_entry() as you are deleting entries within the
loop,
otherwise, this can become an infinite loop. Again, have you tested this
patch
before upload? I am sure this is problematic - when it becomes an
inifinite
loop, below path will hang...
ufshcd_suspend()->ufshpb_suspend()->cancel_jobs()->cancel_delayed_work()
>>
>> And, which lock is protecting rgn->list_expired_rgn? If two
>> read_to_handler works
>> are running in parallel, one can be inserting it to its expired_list
>> while another
>> can be deleting it.
> The timeout handler, being a delayed work, is meant to run every
> polling period.
> Originally, I had it protected from 2 handlers running concurrently,
> But I removed it following Daejun's comment, which I accepted,
> Since it is always scheduled using the same polling period.
But one can set the delay to 0 through sysfs, right?
Thanks,
Can Guo.
>
> Thanks,
> Avri
>
>>
>> Can Guo.
>>
>> > + list_del_init(&rgn->list_expired_rgn);
>> > + spin_lock_irqsave(&hpb->rsp_list_lock, flags);
>> > + ufshpb_update_inactive_info(hpb, rgn->rgn_idx);
>> > + hpb->stats.rb_inactive_cnt++;
>> > + spin_unlock_irqrestore(&hpb->rsp_list_lock, flags);
>> > + }
>> > +
>> > + ufshpb_kick_map_work(hpb);
>> > +
>> > + schedule_delayed_work(&hpb->ufshpb_read_to_work,
>> > + msecs_to_jiffies(POLLING_INTERVAL_MS));
>> > +}
>> > +
>> > static void ufshpb_add_lru_info(struct victim_select_info *lru_info,
>> > struct ufshpb_region *rgn)
>> > {
>> > rgn->rgn_state = HPB_RGN_ACTIVE;
>> > list_add_tail(&rgn->list_lru_rgn, &lru_info->lh_lru_rgn);
>> > atomic_inc(&lru_info->active_cnt);
>> > + if (rgn->hpb->is_hcm) {
>> > + rgn->read_timeout = ktime_add_ms(ktime_get(), READ_TO_MS);
>> > + rgn->read_timeout_expiries = READ_TO_EXPIRIES;
>> > + }
>> > }
>> >
>> > static void ufshpb_hit_lru_info(struct victim_select_info *lru_info,
>> > @@ -1813,6 +1865,7 @@ static int ufshpb_alloc_region_tbl(struct
>> > ufs_hba *hba, struct ufshpb_lu *hpb)
>> >
>> > INIT_LIST_HEAD(&rgn->list_inact_rgn);
>> > INIT_LIST_HEAD(&rgn->list_lru_rgn);
>> > + INIT_LIST_HEAD(&rgn->list_expired_rgn);
>> >
>> > if (rgn_idx == hpb->rgns_per_lu - 1) {
>> > srgn_cnt = ((hpb->srgns_per_lu - 1) %
>> > @@ -1834,6 +1887,7 @@ static int ufshpb_alloc_region_tbl(struct
>> > ufs_hba *hba, struct ufshpb_lu *hpb)
>> > }
>> >
>> > rgn->rgn_flags = 0;
>> > + rgn->hpb = hpb;
>> > }
>> >
>> > return 0;
>> > @@ -2053,6 +2107,8 @@ static int ufshpb_lu_hpb_init(struct ufs_hba
>> > *hba, struct ufshpb_lu *hpb)
>> > ufshpb_normalization_work_handler);
>> > INIT_WORK(&hpb->ufshpb_lun_reset_work,
>> > ufshpb_reset_work_handler);
>> > + INIT_DELAYED_WORK(&hpb->ufshpb_read_to_work,
>> > + ufshpb_read_to_handler);
>> > }
>> >
>> > hpb->map_req_cache = kmem_cache_create("ufshpb_req_cache",
>> > @@ -2087,6 +2143,10 @@ static int ufshpb_lu_hpb_init(struct ufs_hba
>> > *hba, struct ufshpb_lu *hpb)
>> > ufshpb_stat_init(hpb);
>> > ufshpb_param_init(hpb);
>> >
>> > + if (hpb->is_hcm)
>> > + schedule_delayed_work(&hpb->ufshpb_read_to_work,
>> > + msecs_to_jiffies(POLLING_INTERVAL_MS));
>> > +
>> > return 0;
>> >
>> > release_pre_req_mempool:
>> > @@ -2154,6 +2214,7 @@ static void ufshpb_discard_rsp_lists(struct
>> > ufshpb_lu *hpb)
>> > static void ufshpb_cancel_jobs(struct ufshpb_lu *hpb)
>> > {
>> > if (hpb->is_hcm) {
>> > + cancel_delayed_work_sync(&hpb->ufshpb_read_to_work);
>> > cancel_work_sync(&hpb->ufshpb_lun_reset_work);
>> > cancel_work_sync(&hpb->ufshpb_normalization_work);
>> > }
>> > @@ -2264,6 +2325,10 @@ void ufshpb_resume(struct ufs_hba *hba)
>> > continue;
>> > ufshpb_set_state(hpb, HPB_PRESENT);
>> > ufshpb_kick_map_work(hpb);
>> > + if (hpb->is_hcm)
>> > + schedule_delayed_work(&hpb->ufshpb_read_to_work,
>> > + msecs_to_jiffies(POLLING_INTERVAL_MS));
>> > +
>> > }
>> > }
>> >
>> > diff --git a/drivers/scsi/ufs/ufshpb.h b/drivers/scsi/ufs/ufshpb.h
>> > index 37c1b0ea0c0a..b49e9a34267f 100644
>> > --- a/drivers/scsi/ufs/ufshpb.h
>> > +++ b/drivers/scsi/ufs/ufshpb.h
>> > @@ -109,6 +109,7 @@ struct ufshpb_subregion {
>> > };
>> >
>> > struct ufshpb_region {
>> > + struct ufshpb_lu *hpb;
>> > struct ufshpb_subregion *srgn_tbl;
>> > enum HPB_RGN_STATE rgn_state;
>> > int rgn_idx;
>> > @@ -126,6 +127,10 @@ struct ufshpb_region {
>> > /* region reads - for host mode */
>> > spinlock_t rgn_lock;
>> > unsigned int reads;
>> > + /* region "cold" timer - for host mode */
>> > + ktime_t read_timeout;
>> > + unsigned int read_timeout_expiries;
>> > + struct list_head list_expired_rgn;
>> > };
>> >
>> > #define for_each_sub_region(rgn, i, srgn) \
>> > @@ -219,6 +224,7 @@ struct ufshpb_lu {
>> > struct victim_select_info lru_info;
>> > struct work_struct ufshpb_normalization_work;
>> > struct work_struct ufshpb_lun_reset_work;
>> > + struct delayed_work ufshpb_read_to_work;
>> >
>> > /* pinned region information */
>> > u32 lu_pinned_start;
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