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    SubjectRE: [PATCH 5.10 83/83] scsi: ufs: core: Fix task management completion
    Date
    Hi

    This doesn't work. Please drop. Sorry, no idea why I sent it before testing.

    Specifically, in v5.10, ufshcd_tmc_handler() can be called under the same spinlock
    it is using, which deadlocks.

    Regards
    Adrian

    > -----Original Message-----
    > From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > Sent: Monday, October 11, 2021 4:47 PM
    > To: linux-kernel@vger.kernel.org
    > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>;
    > stable@vger.kernel.org; Bart Van Assche <bvanassche@acm.org>; Hunter,
    > Adrian <adrian.hunter@intel.com>; Martin K. Petersen
    > <martin.petersen@oracle.com>
    > Subject: [PATCH 5.10 83/83] scsi: ufs: core: Fix task management completion
    >
    > From: Adrian Hunter <adrian.hunter@intel.com>
    >
    > commit f5ef336fd2e4c36dedae4e7ca66cf5349d6fda62 upstream.
    >
    > The UFS driver uses blk_mq_tagset_busy_iter() when identifying task
    > management requests to complete, however blk_mq_tagset_busy_iter()
    > doesn't
    > work.
    >
    > blk_mq_tagset_busy_iter() only iterates requests dispatched by the block
    > layer. That appears as if it might have started since commit 37f4a24c2469
    > ("blk-mq: centralise related handling into blk_mq_get_driver_tag") which
    > removed 'data->hctx->tags->rqs[rq->tag] = rq' from blk_mq_rq_ctx_init()
    > which gets called:
    >
    > blk_get_request
    > blk_mq_alloc_request
    > __blk_mq_alloc_request
    > blk_mq_rq_ctx_init
    >
    > Since UFS task management requests are not dispatched by the block layer,
    > hctx->tags->rqs[rq->tag] remains NULL, and since
    > blk_mq_tagset_busy_iter()
    > relies on finding requests using hctx->tags->rqs[rq->tag], UFS task
    > management requests are never found by blk_mq_tagset_busy_iter().
    >
    > By using blk_mq_tagset_busy_iter(), the UFS driver was relying on internal
    > details of the block layer, which was fragile and subsequently got
    > broken. Fix by removing the use of blk_mq_tagset_busy_iter() and having
    > the
    > driver keep track of task management requests.
    >
    > Link: https://lore.kernel.org/r/20210922091059.4040-1-
    > adrian.hunter@intel.com
    > Fixes: 1235fc569e0b ("scsi: ufs: core: Fix task management request
    > completion timeout")
    > Fixes: 69a6c269c097 ("scsi: ufs: Use blk_{get,put}_request() to allocate and
    > free TMFs")
    > Cc: stable@vger.kernel.org
    > Tested-by: Bart Van Assche <bvanassche@acm.org>
    > Reviewed-by: Bart Van Assche <bvanassche@acm.org>
    > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
    > Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    >
    > ---
    > drivers/scsi/ufs/ufshcd.c | 54 +++++++++++++++++++++----------------------
    > ---
    > drivers/scsi/ufs/ufshcd.h | 1
    > 2 files changed, 26 insertions(+), 29 deletions(-)
    >
    > --- a/drivers/scsi/ufs/ufshcd.c
    > +++ b/drivers/scsi/ufs/ufshcd.c
    > @@ -6105,27 +6105,6 @@ static irqreturn_t ufshcd_check_errors(s
    > return retval;
    > }
    >
    > -struct ctm_info {
    > - struct ufs_hba *hba;
    > - unsigned long pending;
    > - unsigned int ncpl;
    > -};
    > -
    > -static bool ufshcd_compl_tm(struct request *req, void *priv, bool reserved)
    > -{
    > - struct ctm_info *const ci = priv;
    > - struct completion *c;
    > -
    > - WARN_ON_ONCE(reserved);
    > - if (test_bit(req->tag, &ci->pending))
    > - return true;
    > - ci->ncpl++;
    > - c = req->end_io_data;
    > - if (c)
    > - complete(c);
    > - return true;
    > -}
    > -
    > /**
    > * ufshcd_tmc_handler - handle task management function completion
    > * @hba: per adapter instance
    > @@ -6136,14 +6115,24 @@ static bool ufshcd_compl_tm(struct reque
    > */
    > static irqreturn_t ufshcd_tmc_handler(struct ufs_hba *hba)
    > {
    > - struct request_queue *q = hba->tmf_queue;
    > - struct ctm_info ci = {
    > - .hba = hba,
    > - .pending = ufshcd_readl(hba,
    > REG_UTP_TASK_REQ_DOOR_BELL),
    > - };
    > + unsigned long flags, pending, issued;
    > + irqreturn_t ret = IRQ_NONE;
    > + int tag;
    >
    > - blk_mq_tagset_busy_iter(q->tag_set, ufshcd_compl_tm, &ci);
    > - return ci.ncpl ? IRQ_HANDLED : IRQ_NONE;
    > + pending = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
    > +
    > + spin_lock_irqsave(hba->host->host_lock, flags);
    > + issued = hba->outstanding_tasks & ~pending;
    > + for_each_set_bit(tag, &issued, hba->nutmrs) {
    > + struct request *req = hba->tmf_rqs[tag];
    > + struct completion *c = req->end_io_data;
    > +
    > + complete(c);
    > + ret = IRQ_HANDLED;
    > + }
    > + spin_unlock_irqrestore(hba->host->host_lock, flags);
    > +
    > + return ret;
    > }
    >
    > /**
    > @@ -6273,9 +6262,9 @@ static int __ufshcd_issue_tm_cmd(struct
    > ufshcd_hold(hba, false);
    >
    > spin_lock_irqsave(host->host_lock, flags);
    > - blk_mq_start_request(req);
    >
    > task_tag = req->tag;
    > + hba->tmf_rqs[req->tag] = req;
    > treq->req_header.dword_0 |= cpu_to_be32(task_tag);
    >
    > memcpy(hba->utmrdl_base_addr + task_tag, treq, sizeof(*treq));
    > @@ -6319,6 +6308,7 @@ static int __ufshcd_issue_tm_cmd(struct
    > }
    >
    > spin_lock_irqsave(hba->host->host_lock, flags);
    > + hba->tmf_rqs[req->tag] = NULL;
    > __clear_bit(task_tag, &hba->outstanding_tasks);
    > spin_unlock_irqrestore(hba->host->host_lock, flags);
    >
    > @@ -9246,6 +9236,12 @@ int ufshcd_init(struct ufs_hba *hba, voi
    > err = PTR_ERR(hba->tmf_queue);
    > goto free_tmf_tag_set;
    > }
    > + hba->tmf_rqs = devm_kcalloc(hba->dev, hba->nutmrs,
    > + sizeof(*hba->tmf_rqs), GFP_KERNEL);
    > + if (!hba->tmf_rqs) {
    > + err = -ENOMEM;
    > + goto free_tmf_queue;
    > + }
    >
    > /* Reset the attached device */
    > ufshcd_vops_device_reset(hba);
    > --- a/drivers/scsi/ufs/ufshcd.h
    > +++ b/drivers/scsi/ufs/ufshcd.h
    > @@ -731,6 +731,7 @@ struct ufs_hba {
    >
    > struct blk_mq_tag_set tmf_tag_set;
    > struct request_queue *tmf_queue;
    > + struct request **tmf_rqs;
    >
    > struct uic_command *active_uic_cmd;
    > struct mutex uic_cmd_mutex;
    >

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