RE: [PATCH v5 07/10] scsi: ufshpb: Add "Cold" regions timer

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> 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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