Re: [PATCH v3 07/11] tpm: Replace device number bitmap with IDR

["Stefan Berger" <stefanb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

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Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> wrote on 02/22/2016 
02:06:29 PM:


> 
> On Fri, Feb 19, 2016 at 07:42:04AM -0500, Stefan Berger wrote:
> > +   if (chip_num == TPM_ANY_NUM)
> > +      chip_next = 0;
> > +
> > +   mutex_lock(&idr_lock);
> > +
> > +   do {
> > +      if (chip_num == TPM_ANY_NUM) {
> > +         chip_prev = chip_next;
> > +         chip = idr_get_next(&dev_nums_idr, &chip_next);
> > +      } else
> > +         chip = idr_find_slowpath(&dev_nums_idr, chip_num);
> > +
> > +      if (chip && !tpm_try_get_ops(chip))
> > +         break;
> > +   } while (chip_num == TPM_ANY_NUM && chip_prev != chip_next);
> 
> This while loop doesn't look very good if tpm_try_get_ops fails?
> 
> Maybe like this?
> 
> struct tpm_chip *tpm_chip_find_get(int chip_num)
> {
>    struct tpm_chip *res = NULL;
> 
>    mutex_lock(&idr_lock);
> 
>    if (chip_num == TPM_ANY_NUM) {
>       struct tpm_chip *chip;
> 
>       chip_num = 0;
>       do {
>          chip = idr_get_next(&dev_nums_idr, &chip_num);
>          if (res && !tpm_try_get_ops(chip)) {
>             res = chip;
>             break;
>          }
>       }
>       while (chip);
>    } else {
>       res = idr_find_slowpath(&dev_nums_idr, chip_num);
>       if (res && tpm_try_get_ops(chip))
>          res = NULL;
>    }
> 
>    mutex_unlock(&idr_lock);
> 
>    return res;
> }

        mutex_lock(&idr_lock);

        if (chip_num == TPM_ANY_NUM) {
                chip_num = 0;
                do {
                        chip_prev = chip_num;
                        chip = idr_get_next(&dev_nums_idr, &chip_num);
                        if (chip && !tpm_try_get_ops(chip)) {
                                res = chip;
                                break;
                        }
                } while (chip_prev != chip_num);
        } else {
                chip = idr_find_slowpath(&dev_nums_idr, chip_num);
                if (chip && !tpm_try_get_ops(chip))
                        res = chip;
        }

        mutex_unlock(&idr_lock);



FYI: idr_get_next will return NULL for a chip->dev_num that has nothing 
(NULL) registered; we *may* find something after that again.

   Stefan



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