* [dpdk-dev] [PATCH] eal/reciprocal: fix off by one when divisor is 32bit
@ 2019-09-03 19:16 pbhagavatula
2019-10-15 8:45 ` David Marchand
2019-10-26 14:33 ` [dpdk-dev] " David Marchand
0 siblings, 2 replies; 5+ messages in thread
From: pbhagavatula @ 2019-09-03 19:16 UTC (permalink / raw)
To: stephen, jerinj; +Cc: dev, Pavan Nikhilesh, stable
From: Pavan Nikhilesh <pbhagavatula@marvell.com>
Fix off by one error in 64bit reciprocal division when divisor is 32bit.
Fixes: 6d45659eacb8 ("eal: add u64-bit variant for reciprocal divide")
Cc: stable@dpdk.org
Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
---
Example:
Division failed, 17358247066007716387/244 =
expected 71140356827900476 result 71140356827900477
Division failed, 17541123788887206374/41475 =
expected 422932460250444 result 422932460250445
lib/librte_eal/common/rte_reciprocal.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/lib/librte_eal/common/rte_reciprocal.c b/lib/librte_eal/common/rte_reciprocal.c
index f017d0c28..1c6d10e73 100644
--- a/lib/librte_eal/common/rte_reciprocal.c
+++ b/lib/librte_eal/common/rte_reciprocal.c
@@ -133,12 +133,15 @@ rte_reciprocal_value_u64(uint64_t d)
{
struct rte_reciprocal_u64 R;
uint64_t m;
+ uint64_t r;
int l;
l = 63 - __builtin_clzll(d);
- m = divide_128_div_64_to_64((1ULL << l), 0, d, NULL) << 1;
- m = (1ULL << l) - d ? m + 2 : 1;
+ m = divide_128_div_64_to_64((1ULL << l), 0, d, &r) << 1;
+ if (r << 1 < r || r << 1 >= d)
+ m++;
+ m = (1ULL << l) - d ? m + 1 : 1;
R.m = m;
R.sh1 = l > 1 ? 1 : l;
--
2.23.0
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [dpdk-dev] [PATCH] eal/reciprocal: fix off by one when divisor is 32bit
2019-09-03 19:16 [dpdk-dev] [PATCH] eal/reciprocal: fix off by one when divisor is 32bit pbhagavatula
@ 2019-10-15 8:45 ` David Marchand
2019-10-15 8:56 ` [dpdk-dev] [EXT] " Pavan Nikhilesh Bhagavatula
2019-10-26 14:33 ` [dpdk-dev] " David Marchand
1 sibling, 1 reply; 5+ messages in thread
From: David Marchand @ 2019-10-15 8:45 UTC (permalink / raw)
To: Jerin Jacob Kollanukkaran, Stephen Hemminger
Cc: dev, Pavan Nikhilesh, dpdk stable, Aaron Conole
On Tue, Sep 3, 2019 at 9:17 PM <pbhagavatula@marvell.com> wrote:
>
> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>
> Fix off by one error in 64bit reciprocal division when divisor is 32bit.
>
> Fixes: 6d45659eacb8 ("eal: add u64-bit variant for reciprocal divide")
> Cc: stable@dpdk.org
>
> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
Any review?
Are we missing an update in the unit test to catch this issue?
Thanks.
--
David Marchand
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [dpdk-dev] [EXT] Re: [PATCH] eal/reciprocal: fix off by one when divisor is 32bit
2019-10-15 8:45 ` David Marchand
@ 2019-10-15 8:56 ` Pavan Nikhilesh Bhagavatula
2019-10-15 9:06 ` David Marchand
0 siblings, 1 reply; 5+ messages in thread
From: Pavan Nikhilesh Bhagavatula @ 2019-10-15 8:56 UTC (permalink / raw)
To: David Marchand, Jerin Jacob Kollanukkaran, Stephen Hemminger
Cc: dev, dpdk stable, Aaron Conole
>-----Original Message-----
>From: David Marchand <david.marchand@redhat.com>
>Sent: Tuesday, October 15, 2019 2:16 PM
>To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; Stephen
>Hemminger <stephen@networkplumber.org>
>Cc: dev <dev@dpdk.org>; Pavan Nikhilesh Bhagavatula
><pbhagavatula@marvell.com>; dpdk stable <stable@dpdk.org>; Aaron
>Conole <aconole@redhat.com>
>Subject: Re: [dpdk-dev] [PATCH] eal/reciprocal: fix off by one
>when divisor is 32bit
>On Tue, Sep 3, 2019 at 9:17 PM <pbhagavatula@marvell.com> wrote:
>>
>> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>>
>> Fix off by one error in 64bit reciprocal division when divisor is 32bit.
>>
>> Fixes: 6d45659eacb8 ("eal: add u64-bit variant for reciprocal divide")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
>
>Any review?
>
>Are we missing an update in the unit test to catch this issue?
>Thanks.
We actually caught it in a unit test
>test_reciprocal_division
>
>--
>David Marchand
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [dpdk-dev] [EXT] Re: [PATCH] eal/reciprocal: fix off by one when divisor is 32bit
2019-10-15 8:56 ` [dpdk-dev] [EXT] " Pavan Nikhilesh Bhagavatula
@ 2019-10-15 9:06 ` David Marchand
0 siblings, 0 replies; 5+ messages in thread
From: David Marchand @ 2019-10-15 9:06 UTC (permalink / raw)
To: Pavan Nikhilesh Bhagavatula
Cc: Jerin Jacob Kollanukkaran, Stephen Hemminger, dev, dpdk stable,
Aaron Conole
On Tue, Oct 15, 2019 at 10:56 AM Pavan Nikhilesh Bhagavatula
<pbhagavatula@marvell.com> wrote:
>
>
>
> >-----Original Message-----
> >From: David Marchand <david.marchand@redhat.com>
> >Sent: Tuesday, October 15, 2019 2:16 PM
> >To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; Stephen
> >Hemminger <stephen@networkplumber.org>
> >Cc: dev <dev@dpdk.org>; Pavan Nikhilesh Bhagavatula
> ><pbhagavatula@marvell.com>; dpdk stable <stable@dpdk.org>; Aaron
> >Conole <aconole@redhat.com>
> >Subject: Re: [dpdk-dev] [PATCH] eal/reciprocal: fix off by one
> >when divisor is 32bit
> >On Tue, Sep 3, 2019 at 9:17 PM <pbhagavatula@marvell.com> wrote:
> >>
> >> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> >>
> >> Fix off by one error in 64bit reciprocal division when divisor is 32bit.
> >>
> >> Fixes: 6d45659eacb8 ("eal: add u64-bit variant for reciprocal divide")
> >> Cc: stable@dpdk.org
> >>
> >> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> >
> >Any review?
> >
> >Are we missing an update in the unit test to catch this issue?
> >Thanks.
>
> We actually caught it in a unit test
> >test_reciprocal_division
We had this problem since the very start then.
Both reciprocal_division and reciprocal_division_perf are in the "perf" list.
Can they be promoted to the standard list?
--
David Marchand
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [dpdk-dev] [PATCH] eal/reciprocal: fix off by one when divisor is 32bit
2019-09-03 19:16 [dpdk-dev] [PATCH] eal/reciprocal: fix off by one when divisor is 32bit pbhagavatula
2019-10-15 8:45 ` David Marchand
@ 2019-10-26 14:33 ` David Marchand
1 sibling, 0 replies; 5+ messages in thread
From: David Marchand @ 2019-10-26 14:33 UTC (permalink / raw)
To: Pavan Nikhilesh
Cc: Stephen Hemminger, Jerin Jacob Kollanukkaran, dev, dpdk stable,
Aaron Conole, hannes
On Tue, Sep 3, 2019 at 9:17 PM <pbhagavatula@marvell.com> wrote:
>
> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>
> Fix off by one error in 64bit reciprocal division when divisor is 32bit.
Added log from unit test:
RTE>>reciprocal_division
Validating unsigned 32bit division.
Validating unsigned 64bit division.
Validating unsigned 64bit division with 32bit divisor.
Division failed, 16983222950483802557/819 = expected 20736535959076681
result 20736535959076682
Validating division by power of 2.
Test Failed
>
> Fixes: 6d45659eacb8 ("eal: add u64-bit variant for reciprocal divide")
> Cc: stable@dpdk.org
>
> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
Please continue working on enhancing the functional test so that it
can be part of the standard unit test list.
Thanks.
--
David Marchand
^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-09-03 19:16 [dpdk-dev] [PATCH] eal/reciprocal: fix off by one when divisor is 32bit pbhagavatula
2019-10-15 8:45 ` David Marchand
2019-10-15 8:56 ` [dpdk-dev] [EXT] " Pavan Nikhilesh Bhagavatula
2019-10-15 9:06 ` David Marchand
2019-10-26 14:33 ` [dpdk-dev] " David Marchand
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