RE: [PATCH 5/9] scsi: ufs: add reference counting for scsi block requests
> -Original Message- > From: linux-scsi-ow...@vger.kernel.org [mailto:linux-scsi- > ow...@vger.kernel.org] On Behalf Of Asutosh Das > Sent: Wednesday, February 21, 2018 6:57 AM > To: subha...@codeaurora.org; c...@codeaurora.org; > vivek.gau...@codeaurora.org; rna...@codeaurora.org; > vinholika...@gmail.com; j...@linux.vnet.ibm.com; > martin.peter...@oracle.com > Cc: linux-scsi@vger.kernel.org; Asutosh Das ; > open list > Subject: [PATCH 5/9] scsi: ufs: add reference counting for scsi block requests > > From: Subhash Jadavani > > Currently we call the scsi_block_requests()/scsi_unblock_requests() > whenever we want to block/unblock scsi requests but as there is no > reference counting, nesting of these calls could leave us in undesired state > sometime. Consider following call flow sequence: > 1. func1() calls scsi_block_requests() but calls func2() before >calling scsi_unblock_requests() > 2. func2() calls scsi_block_requests() > 3. func2() calls scsi_unblock_requests() 4. func1() calls > scsi_unblock_requests() > > As there is no reference counting, we will have scsi requests unblocked after > #3 instead of it to be unblocked only after #4. Though we may not have > failures seen with this, we might run into some failures in future. > Better solution would be to fix this by adding reference counting. > > Signed-off-by: Subhash Jadavani > Signed-off-by: Can Guo > Signed-off-by: Asutosh Das > --- > drivers/scsi/ufs/ufshcd.c | 44 > +--- > drivers/scsi/ufs/ufshcd.h | 5 + > 2 files changed, 42 insertions(+), 7 deletions(-) > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index > 7a4df95..987b81b 100644 > --- a/drivers/scsi/ufs/ufshcd.c > +++ b/drivers/scsi/ufs/ufshcd.c > @@ -264,6 +264,36 @@ static inline void ufshcd_disable_irq(struct ufs_hba > *hba) > } > } > > +void ufshcd_scsi_unblock_requests(struct ufs_hba *hba) { > + unsigned long flags; > + bool unblock = false; > + > + spin_lock_irqsave(hba->host->host_lock, flags); > + hba->scsi_block_reqs_cnt--; > + unblock = !hba->scsi_block_reqs_cnt; > + spin_unlock_irqrestore(hba->host->host_lock, flags); > + if (unblock) > + scsi_unblock_requests(hba->host); > +} > +EXPORT_SYMBOL(ufshcd_scsi_unblock_requests); > + > +static inline void __ufshcd_scsi_block_requests(struct ufs_hba *hba) { > + if (!hba->scsi_block_reqs_cnt++) > + scsi_block_requests(hba->host); > +} > + > +void ufshcd_scsi_block_requests(struct ufs_hba *hba) { > + unsigned long flags; > + > + spin_lock_irqsave(hba->host->host_lock, flags); > + __ufshcd_scsi_block_requests(hba); > + spin_unlock_irqrestore(hba->host->host_lock, flags); } > +EXPORT_SYMBOL(ufshcd_scsi_block_requests); > + > /* replace non-printable or non-ASCII characters with spaces */ static > inline > void ufshcd_remove_non_printable(char *val) { @@ -1079,12 +1109,12 @@ > static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba) >* make sure that there are no outstanding requests when >* clock scaling is in progress >*/ > - scsi_block_requests(hba->host); > + ufshcd_scsi_block_requests(hba); > down_write(&hba->clk_scaling_lock); > if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) { > ret = -EBUSY; > up_write(&hba->clk_scaling_lock); > - scsi_unblock_requests(hba->host); > + ufshcd_scsi_unblock_requests(hba); > } > > return ret; > @@ -1093,7 +1123,7 @@ static int ufshcd_clock_scaling_prepare(struct > ufs_hba *hba) static void ufshcd_clock_scaling_unprepare(struct ufs_hba > *hba) { > up_write(&hba->clk_scaling_lock); > - scsi_unblock_requests(hba->host); > + ufshcd_scsi_unblock_requests(hba); > } > > /** > @@ -1413,7 +1443,7 @@ static void ufshcd_ungate_work(struct work_struct > *work) > hba->clk_gating.is_suspended = false; > } > unblock_reqs: > - scsi_unblock_requests(hba->host); > + ufshcd_scsi_unblock_requests(hba); > } > > /** > @@ -1469,7 +1499,7 @@ int ufshcd_hold(struct ufs_hba *hba, bool async) >* work and to enable clocks. >*/ > case CLKS_OFF: > - scsi_block_requests(hba->host); > + __ufshcd_scsi_block_requests(hba); > hba->clk_gating.state = REQ_CLKS_ON; > trace_ufshcd_clk_gating(dev_name(hba->dev), > hba->clk_gating.state); > @@ -5197,7 +5227,7 @@ static void ufshcd_err_handler(struct work_struct > *work) > > out: > spin_unlock_irqrestore(hba->host->host_lock, flags); > - scsi_unblock_requests(hba->host); > + ufshcd_scsi_unblock_requests(hba); > ufshcd_release(hba); > pm_runtime_put_sync(hba->dev); > } > @@ -5299,7 +5329,7 @@ static void ufshcd_check_errors(struct ufs_hba > *hba) > /* handle fatal errors only w
Re: [PATCH 5/9] scsi: ufs: add reference counting for scsi block requests
On 2/21/2018 6:48 PM, Stanislav Nijnikov wrote: -Original Message- From: linux-scsi-ow...@vger.kernel.org [mailto:linux-scsi- ow...@vger.kernel.org] On Behalf Of Asutosh Das Sent: Wednesday, February 21, 2018 6:57 AM To: subha...@codeaurora.org; c...@codeaurora.org; vivek.gau...@codeaurora.org; rna...@codeaurora.org; vinholika...@gmail.com; j...@linux.vnet.ibm.com; martin.peter...@oracle.com Cc: linux-scsi@vger.kernel.org; Asutosh Das ; open list Subject: [PATCH 5/9] scsi: ufs: add reference counting for scsi block requests From: Subhash Jadavani Currently we call the scsi_block_requests()/scsi_unblock_requests() whenever we want to block/unblock scsi requests but as there is no reference counting, nesting of these calls could leave us in undesired state sometime. Consider following call flow sequence: 1. func1() calls scsi_block_requests() but calls func2() before calling scsi_unblock_requests() 2. func2() calls scsi_block_requests() 3. func2() calls scsi_unblock_requests() 4. func1() calls scsi_unblock_requests() As there is no reference counting, we will have scsi requests unblocked after #3 instead of it to be unblocked only after #4. Though we may not have failures seen with this, we might run into some failures in future. Better solution would be to fix this by adding reference counting. Signed-off-by: Subhash Jadavani Signed-off-by: Can Guo Signed-off-by: Asutosh Das --- drivers/scsi/ufs/ufshcd.c | 44 +--- drivers/scsi/ufs/ufshcd.h | 5 + 2 files changed, 42 insertions(+), 7 deletions(-) diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 7a4df95..987b81b 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -264,6 +264,36 @@ static inline void ufshcd_disable_irq(struct ufs_hba *hba) } } +void ufshcd_scsi_unblock_requests(struct ufs_hba *hba) { + unsigned long flags; + bool unblock = false; + + spin_lock_irqsave(hba->host->host_lock, flags); + hba->scsi_block_reqs_cnt--; + unblock = !hba->scsi_block_reqs_cnt; + spin_unlock_irqrestore(hba->host->host_lock, flags); + if (unblock) + scsi_unblock_requests(hba->host); +} +EXPORT_SYMBOL(ufshcd_scsi_unblock_requests); + +static inline void __ufshcd_scsi_block_requests(struct ufs_hba *hba) { + if (!hba->scsi_block_reqs_cnt++) + scsi_block_requests(hba->host); +} + +void ufshcd_scsi_block_requests(struct ufs_hba *hba) { + unsigned long flags; + + spin_lock_irqsave(hba->host->host_lock, flags); + __ufshcd_scsi_block_requests(hba); + spin_unlock_irqrestore(hba->host->host_lock, flags); } +EXPORT_SYMBOL(ufshcd_scsi_block_requests); + /* replace non-printable or non-ASCII characters with spaces */ static inline void ufshcd_remove_non_printable(char *val) { @@ -1079,12 +1109,12 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba) * make sure that there are no outstanding requests when * clock scaling is in progress */ - scsi_block_requests(hba->host); + ufshcd_scsi_block_requests(hba); down_write(&hba->clk_scaling_lock); if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) { ret = -EBUSY; up_write(&hba->clk_scaling_lock); - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); } return ret; @@ -1093,7 +1123,7 @@ static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba) static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba) { up_write(&hba->clk_scaling_lock); - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); } /** @@ -1413,7 +1443,7 @@ static void ufshcd_ungate_work(struct work_struct *work) hba->clk_gating.is_suspended = false; } unblock_reqs: - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); } /** @@ -1469,7 +1499,7 @@ int ufshcd_hold(struct ufs_hba *hba, bool async) * work and to enable clocks. */ case CLKS_OFF: - scsi_block_requests(hba->host); + __ufshcd_scsi_block_requests(hba); hba->clk_gating.state = REQ_CLKS_ON; trace_ufshcd_clk_gating(dev_name(hba->dev), hba->clk_gating.state); @@ -5197,7 +5227,7 @@ static void ufshcd_err_handler(struct work_struct *work) out: spin_unlock_irqrestore(hba->host->host_lock, flags); - scsi_unblock_requests(hba->host); + ufshcd_scsi_unblock_requests(hba); ufshcd_release(hba); pm_runtime_put_sync(hba->dev); } @@ -5299,7 +5329,7 @@ static void ufshcd_check_errors(struct ufs_hba *hba) /* handle fatal errors only when link is functional */ if (hba->ufshcd_state == UFSHCD_STATE_OPERATIONAL) {