Re: [PATCH v7 5/8] scsi: ufs: Fix ufshcd_hold() caused scheduling while atomic

[Can Guo]

On 2020-02-06 18:28, Avri Altman wrote:
> Hi,
>
> > The async version of ufshcd_hold(async == true), which is only called
> > in queuecommand path as for now, is expected to work in atomic 
> > context,
> > thus it should not sleep or schedule out. When it runs into the 
> > condition
> > that clocks are ON but link is still in hibern8 state, it should bail 
> > out
> > without flushing the clock ungate work.
>
> Fixes: f2a785ac2312 (scsi: ufshcd: Fix race between clk scaling and 
> ungate work)

Sorry, missed this one, if another version is needed, I will add this 
line.

> > Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
> > Reviewed-by: Hongwu Su <hongwus@xxxxxxxxxxxxxx>
> > Reviewed-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> > Reviewed-by: Bean Huo <beanhuo@xxxxxxxxxx>
> > Reviewed-by: Stanley Chu <stanley.chu@xxxxxxxxxxxx>
> > ---
> >  drivers/scsi/ufs/ufshcd.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > index bbc2607..e8f7f9d 100644
> > --- a/drivers/scsi/ufs/ufshcd.c
> > +++ b/drivers/scsi/ufs/ufshcd.c
> > @@ -1518,6 +1518,11 @@ int ufshcd_hold(struct ufs_hba *hba, bool 
> > async)
> >                  */
> >                 if (ufshcd_can_hibern8_during_gating(hba) &&
> >                     ufshcd_is_link_hibern8(hba)) {
> > +                       if (async) {
> > +                               rc = -EAGAIN;
> > +                               hba->clk_gating.active_reqs--;
> > +                               break;
> > +                       }
> >                         spin_unlock_irqrestore(hba->host->host_lock, 
> > flags);
> >                         flush_work(&hba->clk_gating.ungate_work);
> >                         spin_lock_irqsave(hba->host->host_lock, 
> > flags);
> Since now the above code is shared in all cases,
> Maybe find a more economical way to pack it?
>
> Thanks,
> Avri

There are only 2 of this same code pieces in ufshcd_hold() and located
in different cases, meanwhile there can be fall through, I don't see
a good way to pack it, can you suggest if you have any ideas?

Regards,
Can Guo.

> > --
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > Forum,
> > a Linux Foundation Collaborative Project