When a task needs to accept memory it will scan the accepting_list
to see if any ranges already being processed by other tasks overlap
with its range. Due to an off-by-one in the range comparisons, a task
might falsely determine that an overlapping range is being accepted,
leading to an unnecessary delay before it begins processing the range.
Fix the off-by-one in the range comparison to prevent this and slightly
improve performance.
Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
Link: https://lore.kernel.org/linux-mm/[email protected]/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
Reviewed-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Michael Roth <[email protected]>
---
v2:
* Improve commit message terminology (Kirill)
---
drivers/firmware/efi/unaccepted_memory.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
index 135278ddaf62..79fb687bb90f 100644
--- a/drivers/firmware/efi/unaccepted_memory.c
+++ b/drivers/firmware/efi/unaccepted_memory.c
@@ -100,7 +100,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
* overlap on physical address level.
*/
list_for_each_entry(entry, &accepting_list, list) {
- if (entry->end < range.start)
+ if (entry->end <= range.start)
continue;
if (entry->start >= range.end)
continue;
--
2.25.1
On 11/3/23 16:13, Michael Roth wrote:
> When a task needs to accept memory it will scan the accepting_list
> to see if any ranges already being processed by other tasks overlap
> with its range. Due to an off-by-one in the range comparisons, a task
> might falsely determine that an overlapping range is being accepted,
> leading to an unnecessary delay before it begins processing the range.
>
> Fix the off-by-one in the range comparison to prevent this and slightly
> improve performance.
>
> Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
> Link: https://lore.kernel.org/linux-mm/[email protected]/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
> Reviewed-by: Kirill A. Shutemov <[email protected]>
> Signed-off-by: Michael Roth <[email protected]>
More justification for introducing a common ranges_overlap() helper somewhere :)
Acked-by: Vlastimil Babka <[email protected]>
> ---
> v2:
> * Improve commit message terminology (Kirill)
> ---
> drivers/firmware/efi/unaccepted_memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
> index 135278ddaf62..79fb687bb90f 100644
> --- a/drivers/firmware/efi/unaccepted_memory.c
> +++ b/drivers/firmware/efi/unaccepted_memory.c
> @@ -100,7 +100,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
> * overlap on physical address level.
> */
> list_for_each_entry(entry, &accepting_list, list) {
> - if (entry->end < range.start)
> + if (entry->end <= range.start)
> continue;
> if (entry->start >= range.end)
> continue;
On 11/8/23 12:21, Ard Biesheuvel wrote:
> On Fri, 3 Nov 2023 at 16:30, Vlastimil Babka <[email protected]> wrote:
>>
>> On 11/3/23 16:13, Michael Roth wrote:
>> > When a task needs to accept memory it will scan the accepting_list
>> > to see if any ranges already being processed by other tasks overlap
>> > with its range. Due to an off-by-one in the range comparisons, a task
>> > might falsely determine that an overlapping range is being accepted,
>> > leading to an unnecessary delay before it begins processing the range.
>> >
>> > Fix the off-by-one in the range comparison to prevent this and slightly
>> > improve performance.
>> >
>> > Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
>> > Link: https://lore.kernel.org/linux-mm/[email protected]/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
>> > Reviewed-by: Kirill A. Shutemov <[email protected]>
>> > Signed-off-by: Michael Roth <[email protected]>
>>
>> More justification for introducing a common ranges_overlap() helper somewhere :)
>>
>> Acked-by: Vlastimil Babka <[email protected]>
>>
>
> Thanks, I'll take this as a fix.
Ping, can't see it in mainline nor -next?
>
>> > ---
>> > v2:
>> > * Improve commit message terminology (Kirill)
>> > ---
>> > drivers/firmware/efi/unaccepted_memory.c | 2 +-
>> > 1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
>> > index 135278ddaf62..79fb687bb90f 100644
>> > --- a/drivers/firmware/efi/unaccepted_memory.c
>> > +++ b/drivers/firmware/efi/unaccepted_memory.c
>> > @@ -100,7 +100,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
>> > * overlap on physical address level.
>> > */
>> > list_for_each_entry(entry, &accepting_list, list) {
>> > - if (entry->end < range.start)
>> > + if (entry->end <= range.start)
>> > continue;
>> > if (entry->start >= range.end)
>> > continue;
>>
>
On Tue, 28 Nov 2023 at 12:25, Vlastimil Babka <[email protected]> wrote:
>
> On 11/8/23 12:21, Ard Biesheuvel wrote:
> > On Fri, 3 Nov 2023 at 16:30, Vlastimil Babka <[email protected]> wrote:
> >>
> >> On 11/3/23 16:13, Michael Roth wrote:
> >> > When a task needs to accept memory it will scan the accepting_list
> >> > to see if any ranges already being processed by other tasks overlap
> >> > with its range. Due to an off-by-one in the range comparisons, a task
> >> > might falsely determine that an overlapping range is being accepted,
> >> > leading to an unnecessary delay before it begins processing the range.
> >> >
> >> > Fix the off-by-one in the range comparison to prevent this and slightly
> >> > improve performance.
> >> >
> >> > Fixes: 50e782a86c98 ("efi/unaccepted: Fix soft lockups caused by parallel memory acceptance")
> >> > Link: https://lore.kernel.org/linux-mm/[email protected]/T/#me2eceb9906fcae5fe958b3fe88e41f920f8335b6
> >> > Reviewed-by: Kirill A. Shutemov <[email protected]>
> >> > Signed-off-by: Michael Roth <[email protected]>
> >>
> >> More justification for introducing a common ranges_overlap() helper somewhere :)
> >>
> >> Acked-by: Vlastimil Babka <[email protected]>
> >>
> >
> > Thanks, I'll take this as a fix.
>
> Ping, can't see it in mainline nor -next?
>
Apologies - queued up now.