| Message ID | 1579764349-15578-2-git-send-email-cang@codeaurora.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | UFS driver general fixes bundle 4 | expand |
Hi, Can > /* TODO: handle Reject UPIU Response */ @@ -5215,7 > +5222,14 @@ static void ufshcd_exception_event_handler(struct work_struct > *work) > > out: > scsi_unblock_requests(hba->host); > - pm_runtime_put_sync(hba->dev); > + /* > + * pm_runtime_get_noresume is called while scheduling > + * eeh_work to avoid suspend racing with exception work. > + * Hence decrement usage counter using pm_runtime_put_noidle > + * to allow suspend on completion of exception event handler. > + */ > + pm_runtime_put_noidle(hba->dev); > + pm_runtime_put(hba->dev); > return; > } > Rebased this patch. Thanks, //Bean
On 2020-01-22 23:25, Can Guo wrote: > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > index 1201578..c2de29f 100644 > --- a/drivers/scsi/ufs/ufshcd.c > +++ b/drivers/scsi/ufs/ufshcd.c > @@ -4760,8 +4760,15 @@ static void ufshcd_slave_destroy(struct scsi_device *sdev) > * UFS device needs urgent BKOPs. > */ > if (!hba->pm_op_in_progress && > - ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) > - schedule_work(&hba->eeh_work); > + ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) { > + /* > + * Prevent suspend once eeh_work is scheduled > + * to avoid deadlock between ufshcd_suspend > + * and exception event handler. > + */ > + if (schedule_work(&hba->eeh_work)) > + pm_runtime_get_noresume(hba->dev); > + } Please combine the two logical tests with "&&" instead of nesting two if-statements inside each other. > break; > case UPIU_TRANSACTION_REJECT_UPIU: > /* TODO: handle Reject UPIU Response */ > @@ -5215,7 +5222,14 @@ static void ufshcd_exception_event_handler(struct work_struct *work) > > out: > scsi_unblock_requests(hba->host); > - pm_runtime_put_sync(hba->dev); > + /* > + * pm_runtime_get_noresume is called while scheduling > + * eeh_work to avoid suspend racing with exception work. > + * Hence decrement usage counter using pm_runtime_put_noidle > + * to allow suspend on completion of exception event handler. > + */ > + pm_runtime_put_noidle(hba->dev); > + pm_runtime_put(hba->dev); > return; > } > > @@ -7901,6 +7915,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op) > goto enable_gating; > } > > + flush_work(&hba->eeh_work); > ret = ufshcd_link_state_transition(hba, req_link_state, 1); > if (ret) > goto set_dev_active; I think this patch introduces a new race condition, namely the following: - ufshcd_slave_destroy() tests pm_op_in_progress and reads the value zero from that variable. - ufshcd_suspend() sets hba->pm_op_in_progress to one. - ufshcd_slave_destroy() calls schedule_work(). How about fixing this race condition by calling pm_runtime_get_noresume() before checking pm_op_in_progress and by reallowing resume if no work is scheduled? Thanks, Bart.
On 2020-01-26 11:29, Bart Van Assche wrote: > On 2020-01-22 23:25, Can Guo wrote: >> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c >> index 1201578..c2de29f 100644 >> --- a/drivers/scsi/ufs/ufshcd.c >> +++ b/drivers/scsi/ufs/ufshcd.c >> @@ -4760,8 +4760,15 @@ static void ufshcd_slave_destroy(struct >> scsi_device *sdev) >> * UFS device needs urgent BKOPs. >> */ >> if (!hba->pm_op_in_progress && >> - ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) >> - schedule_work(&hba->eeh_work); >> + ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) { >> + /* >> + * Prevent suspend once eeh_work is scheduled >> + * to avoid deadlock between ufshcd_suspend >> + * and exception event handler. >> + */ >> + if (schedule_work(&hba->eeh_work)) >> + pm_runtime_get_noresume(hba->dev); >> + } > > Please combine the two logical tests with "&&" instead of nesting two > if-statements inside each other. > >> break; >> case UPIU_TRANSACTION_REJECT_UPIU: >> /* TODO: handle Reject UPIU Response */ >> @@ -5215,7 +5222,14 @@ static void >> ufshcd_exception_event_handler(struct work_struct *work) >> >> out: >> scsi_unblock_requests(hba->host); >> - pm_runtime_put_sync(hba->dev); >> + /* >> + * pm_runtime_get_noresume is called while scheduling >> + * eeh_work to avoid suspend racing with exception work. >> + * Hence decrement usage counter using pm_runtime_put_noidle >> + * to allow suspend on completion of exception event handler. >> + */ >> + pm_runtime_put_noidle(hba->dev); >> + pm_runtime_put(hba->dev); >> return; >> } >> >> @@ -7901,6 +7915,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, >> enum ufs_pm_op pm_op) >> goto enable_gating; >> } >> >> + flush_work(&hba->eeh_work); >> ret = ufshcd_link_state_transition(hba, req_link_state, 1); >> if (ret) >> goto set_dev_active; > > I think this patch introduces a new race condition, namely the > following: > - ufshcd_slave_destroy() tests pm_op_in_progress and reads the value > zero from that variable. > - ufshcd_suspend() sets hba->pm_op_in_progress to one. > - ufshcd_slave_destroy() calls schedule_work(). > > How about fixing this race condition by calling > pm_runtime_get_noresume() before checking pm_op_in_progress and by > reallowing resume if no work is scheduled? > > Thanks, > > Bart. Hi Bart, If you apply this patch, you will find the change is not in ufshcd_slave_destroy(), but in ufshcd_transfer_rsp_status(). So the racing you mentioned above does not exist. Thanks, Can Guo.
On 2020-02-02 22:23, Can Guo wrote: > On 2020-01-26 11:29, Bart Van Assche wrote: >> On 2020-01-22 23:25, Can Guo wrote: >>> break; >>> case UPIU_TRANSACTION_REJECT_UPIU: >>> /* TODO: handle Reject UPIU Response */ >>> @@ -5215,7 +5222,14 @@ static void >>> ufshcd_exception_event_handler(struct work_struct *work) >>> >>> out: >>> scsi_unblock_requests(hba->host); >>> - pm_runtime_put_sync(hba->dev); >>> + /* >>> + * pm_runtime_get_noresume is called while scheduling >>> + * eeh_work to avoid suspend racing with exception work. >>> + * Hence decrement usage counter using pm_runtime_put_noidle >>> + * to allow suspend on completion of exception event handler. >>> + */ >>> + pm_runtime_put_noidle(hba->dev); >>> + pm_runtime_put(hba->dev); >>> return; >>> } >>> >>> @@ -7901,6 +7915,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, >>> enum ufs_pm_op pm_op) >>> goto enable_gating; >>> } >>> >>> + flush_work(&hba->eeh_work); >>> ret = ufshcd_link_state_transition(hba, req_link_state, 1); >>> if (ret) >>> goto set_dev_active; >> >> I think this patch introduces a new race condition, namely the following: >> - ufshcd_slave_destroy() tests pm_op_in_progress and reads the value >> zero from that variable. >> - ufshcd_suspend() sets hba->pm_op_in_progress to one. >> - ufshcd_slave_destroy() calls schedule_work(). >> >> How about fixing this race condition by calling >> pm_runtime_get_noresume() before checking pm_op_in_progress and by >> reallowing resume if no work is scheduled? > > If you apply this patch, you will find the change is not in > ufshcd_slave_destroy(), but in ufshcd_transfer_rsp_status(). > So the racing you mentioned above does not exist. Hi Can, Apparently I got a function name wrong. Can the following race condition happen: - ufshcd_transfer_rsp_status() tests pm_op_in_progress and reads the value zero from that variable. - ufshcd_suspend() sets hba->pm_op_in_progress to one. - ufshcd_suspend() calls flush_work(&hba->eeh_work). - ufshcd_transfer_rsp_status() calls schedule_work(&hba->eeh_work). Thanks, Bart.
On 2020-02-04 11:12, Bart Van Assche wrote: > On 2020-02-02 22:23, Can Guo wrote: >> On 2020-01-26 11:29, Bart Van Assche wrote: >>> On 2020-01-22 23:25, Can Guo wrote: >>>> break; >>>> case UPIU_TRANSACTION_REJECT_UPIU: >>>> /* TODO: handle Reject UPIU Response */ >>>> @@ -5215,7 +5222,14 @@ static void >>>> ufshcd_exception_event_handler(struct work_struct *work) >>>> >>>> out: >>>> scsi_unblock_requests(hba->host); >>>> - pm_runtime_put_sync(hba->dev); >>>> + /* >>>> + * pm_runtime_get_noresume is called while scheduling >>>> + * eeh_work to avoid suspend racing with exception work. >>>> + * Hence decrement usage counter using pm_runtime_put_noidle >>>> + * to allow suspend on completion of exception event handler. >>>> + */ >>>> + pm_runtime_put_noidle(hba->dev); >>>> + pm_runtime_put(hba->dev); >>>> return; >>>> } >>>> >>>> @@ -7901,6 +7915,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, >>>> enum ufs_pm_op pm_op) >>>> goto enable_gating; >>>> } >>>> >>>> + flush_work(&hba->eeh_work); >>>> ret = ufshcd_link_state_transition(hba, req_link_state, 1); >>>> if (ret) >>>> goto set_dev_active; >>> >>> I think this patch introduces a new race condition, namely the >>> following: >>> - ufshcd_slave_destroy() tests pm_op_in_progress and reads the value >>> zero from that variable. >>> - ufshcd_suspend() sets hba->pm_op_in_progress to one. >>> - ufshcd_slave_destroy() calls schedule_work(). >>> >>> How about fixing this race condition by calling >>> pm_runtime_get_noresume() before checking pm_op_in_progress and by >>> reallowing resume if no work is scheduled? >> >> If you apply this patch, you will find the change is not in >> ufshcd_slave_destroy(), but in ufshcd_transfer_rsp_status(). >> So the racing you mentioned above does not exist. > > Hi Can, > > Apparently I got a function name wrong. Can the following race > condition > happen: > - ufshcd_transfer_rsp_status() tests pm_op_in_progress and reads the > value zero from that variable. > - ufshcd_suspend() sets hba->pm_op_in_progress to one. > - ufshcd_suspend() calls flush_work(&hba->eeh_work). > - ufshcd_transfer_rsp_status() calls schedule_work(&hba->eeh_work). > > Thanks, > > Bart. Hi Bart, The sequence you mentioned is not possible. In normal cases, before ufshcd_transfer_rsp_status() returns, ufshcd_suspend() would not be called (unless you intentionally call ufshcd_suspend() to screw it). Because ufshcd_transfer_rsp_status() is called from __ufshcd_transfer_req_compl(), which is being used by either UFS IRQ handler or err handler. Meanwhile, in __ufshcd_transfer_req_compl(), scsi_done() is called only after ufshcd_transfer_rsp_status() returns. When we are here, it means UFS driver is still handling requests/tasks, so suspend would not kick start at this moment, either runtime suspend or system suspend. And this is why below lines work, calling pm_runtime_get_noresume() within ufshcd_transfer_rsp_status() can prevent runtime suspend from happening after we leave ufshcd_transfer_rsp_status(). + if (schedule_work(&hba->eeh_work)) + pm_runtime_get_noresume(hba->dev); Thanks, Can Guo.
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index 1201578..c2de29f 100644 --- a/drivers/scsi/ufs/ufshcd.c +++ b/drivers/scsi/ufs/ufshcd.c @@ -4760,8 +4760,15 @@ static void ufshcd_slave_destroy(struct scsi_device *sdev) * UFS device needs urgent BKOPs. */ if (!hba->pm_op_in_progress && - ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) - schedule_work(&hba->eeh_work); + ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) { + /* + * Prevent suspend once eeh_work is scheduled + * to avoid deadlock between ufshcd_suspend + * and exception event handler. + */ + if (schedule_work(&hba->eeh_work)) + pm_runtime_get_noresume(hba->dev); + } break; case UPIU_TRANSACTION_REJECT_UPIU: /* TODO: handle Reject UPIU Response */ @@ -5215,7 +5222,14 @@ static void ufshcd_exception_event_handler(struct work_struct *work) out: scsi_unblock_requests(hba->host); - pm_runtime_put_sync(hba->dev); + /* + * pm_runtime_get_noresume is called while scheduling + * eeh_work to avoid suspend racing with exception work. + * Hence decrement usage counter using pm_runtime_put_noidle + * to allow suspend on completion of exception event handler. + */ + pm_runtime_put_noidle(hba->dev); + pm_runtime_put(hba->dev); return; } @@ -7901,6 +7915,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op) goto enable_gating; } + flush_work(&hba->eeh_work); ret = ufshcd_link_state_transition(hba, req_link_state, 1); if (ret) goto set_dev_active;