On 6/6/19 11:44 AM, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
>
> The wait_event_timeout macro already tests the condition as its first
> action, so there is no reason to open code another version of this, all
> that does is skip the might_sleep() debugging in common cases, which is
> not helpful.
>
> Further, based on prior patches, we can no simplify the required condition
"now simplify"
> test:
> - If range is valid memory then so is range->hmm
> - If hmm_release() has run then range->valid is set to false
> at the same time as dead, so no reason to check both.
> - A valid hmm has a valid hmm->mm.
>
> Also, add the READ_ONCE for range->valid as there is no lock held here.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
> Reviewed-by: Jérôme Glisse <jglisse@xxxxxxxxxx>
> ---
> include/linux/hmm.h | 12 ++----------
> 1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> index 4ee3acabe5ed22..2ab35b40992b24 100644
> --- a/include/linux/hmm.h
> +++ b/include/linux/hmm.h
> @@ -218,17 +218,9 @@ static inline unsigned long hmm_range_page_size(const struct hmm_range *range)
> static inline bool hmm_range_wait_until_valid(struct hmm_range *range,
> unsigned long timeout)
> {
> - /* Check if mm is dead ? */
> - if (range->hmm == NULL || range->hmm->dead || range->hmm->mm == NULL) {
> - range->valid = false;
> - return false;
> - }
> - if (range->valid)
> - return true;
> - wait_event_timeout(range->hmm->wq, range->valid || range->hmm->dead,
> + wait_event_timeout(range->hmm->wq, range->valid,
> msecs_to_jiffies(timeout));
> - /* Return current valid status just in case we get lucky */
> - return range->valid;
> + return READ_ONCE(range->valid);
Just to ensure that I actually understand the model: I'm assuming that the
READ_ONCE is there solely to ensure that range->valid is read *after* the
wait_event_timeout() returns. Is that correct?
> }
>
> /*
>
In any case, it looks good, so:
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
thanks,
--
John Hubbard
NVIDIA
