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Date: Wed, 17 Mar 2021 07:55:46 +0000
From: Avri Altman <Avri.Altman@....com>
To: Can Guo <cang@...eaurora.org>
CC: "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
"Martin K . Petersen" <martin.petersen@...cle.com>,
"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"gregkh@...uxfoundation.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" <alim.akhtar@...sung.com>,
"asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
Zang Leigang <zangleigang@...ilicon.com>,
Avi Shchislowski <Avi.Shchislowski@....com>,
Bean Huo <beanhuo@...ron.com>,
"stanley.chu@...iatek.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()
Ahh - yes. You are right. Originally I used list_for_each_entry_safe.
Not sure why I changed it here. Will fix it.
I openly disclosed that I am testing the code on gs20 and mi10.
Those are v4.19 platforms, and I am using a driver adopted from the original public hpb driver
Published by Samsung with the gs20 code.
I am also concern as those drivers are drifted apart as the review process commences.
Will try to bring-up a more advanced platform (gs21) and apply the mainline hpb driver.
>
> >>
> >> 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?
Will restore the protection. Thanks.
Thanks,
Avri
>
> 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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