2023-04-12 03:14:14

by Yan Yan(cailing)

Subject: [PATCH v1 1/3] sched/debug: use int type and fix wrong print for rq->nr_uninterruptible

commit e6fe3f422be1 ("sched: Make multiple runqueue task counters
32-bit") changed rq->nr_uninterruptible from 'unsigned long'
to 'unsigned int', but left the wrong print to
/sys/kernel/debug/sched/debug and to the console.

For example:
Current type is 'unsigned int' and value is fffffff7, and the print
will run the sentences,
"do { \
if (sizeof(rq->x) == 4) \
SEQ_printf(m, " .%-30s: %ld\n", #x, (long)(rq->x)); \
else \
SEQ_printf(m, " .%-30s: %Ld\n", #x, (long long)(rq->x));\
} while (0)"

The result will be 4294967287 on 64-bit machines to print (long)(rq->x)
while old type 'unsigned long' will print -9.

And the other places that use its value will cast to int to return
expected output, so we convert its type from 'unsigned int' to int.

Signed-off-by: Yan Yan <[email protected]>
---
kernel/sched/loadavg.c | 2 +-
kernel/sched/sched.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c
index 52c8f8226b0d..b9867495fe8b 100644
--- a/kernel/sched/loadavg.c
+++ b/kernel/sched/loadavg.c
@@ -80,7 +80,7 @@ long calc_load_fold_active(struct rq *this_rq, long adjust)
long nr_active, delta = 0;

nr_active = this_rq->nr_running - adjust;
- nr_active += (int)this_rq->nr_uninterruptible;
+ nr_active += this_rq->nr_uninterruptible;

if (nr_active != this_rq->calc_load_active) {
delta = nr_active - this_rq->calc_load_active;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 060616944d7a..23c643948331 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1006,7 +1006,7 @@ struct rq {
* one CPU and if it got migrated afterwards it may decrease
* it on another CPU. Always updated under the runqueue lock:
*/
- unsigned int nr_uninterruptible;
+ int nr_uninterruptible;

struct task_struct __rcu *curr;
struct task_struct *idle;
--
2.32.0.3.g01195cf9f

2023-04-25 12:28:08

by Yan Yan(cailing)

Subject: Re: [PATCH v1 1/3] sched/debug: use int type and fix wrong print for rq->nr_uninterruptible

在 2023/4/19 15:46, 晏艳 写道:
>
>
> 在 2023/4/12 11:07, 晏艳(采苓) 写道:
>> commit e6fe3f422be1 ("sched: Make multiple runqueue task counters
>> 32-bit") changed rq->nr_uninterruptible from 'unsigned long'
>> to 'unsigned int', but left the wrong print to
>> /sys/kernel/debug/sched/debug and to the console.
>>
>> For example:
>> Current type is 'unsigned int' and value is fffffff7, and the print
>> will run the sentences,
>> "do { \
>> if (sizeof(rq->x) == 4) \
>> SEQ_printf(m, " .%-30s: %ld\n", #x, (long)(rq->x)); \
>> else \
>> SEQ_printf(m, " .%-30s: %Ld\n", #x, (long long)(rq->x));\
>> } while (0)"
>>
>> The result will be 4294967287 on 64-bit machines to print (long)(rq->x)
>> while old type 'unsigned long' will print -9.
>>
>> And the other places that use its value will cast to int to return
>> expected output, so we convert its type from 'unsigned int' to int.
>>
>> Signed-off-by: Yan Yan<[email protected]>
>> ---
>> kernel/sched/loadavg.c | 2 +-
>> kernel/sched/sched.h | 2 +-
>> 2 files changed, 2 insertions(+), 2 deletions(-)
> Ping, any comment?
>
> thanks,
> -Yan Yan

Ping, any comment?

thanks,

-Yan Yan

>> diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c
>> index 52c8f8226b0d..b9867495fe8b 100644
>> --- a/kernel/sched/loadavg.c
>> +++ b/kernel/sched/loadavg.c
>> @@ -80,7 +80,7 @@ long calc_load_fold_active(struct rq *this_rq, long adjust)
>> long nr_active, delta = 0;
>>
>> nr_active = this_rq->nr_running - adjust;
>> - nr_active += (int)this_rq->nr_uninterruptible;
>> + nr_active += this_rq->nr_uninterruptible;
>>
>> if (nr_active != this_rq->calc_load_active) {
>> delta = nr_active - this_rq->calc_load_active;
>> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
>> index 060616944d7a..23c643948331 100644
>> --- a/kernel/sched/sched.h
>> +++ b/kernel/sched/sched.h
>> @@ -1006,7 +1006,7 @@ struct rq {
>> * one CPU and if it got migrated afterwards it may decrease
>> * it on another CPU. Always updated under the runqueue lock:
>> */
>> - unsigned int nr_uninterruptible;
>> + int nr_uninterruptible;
>>
>> struct task_struct __rcu *curr;
>> struct task_struct *idle;

2023-04-25 12:52:48

by Peter Zijlstra

Subject: Re: [PATCH v1 1/3] sched/debug: use int type and fix wrong print for rq->nr_uninterruptible

On Wed, Apr 12, 2023 at 11:07:29AM +0800, 晏艳(采苓) wrote:
> commit e6fe3f422be1 ("sched: Make multiple runqueue task counters
> 32-bit") changed rq->nr_uninterruptible from 'unsigned long'
> to 'unsigned int', but left the wrong print to
> /sys/kernel/debug/sched/debug and to the console.
>
> For example:
> Current type is 'unsigned int' and value is fffffff7, and the print
> will run the sentences,
> "do { \
> if (sizeof(rq->x) == 4) \
> SEQ_printf(m, " .%-30s: %ld\n", #x, (long)(rq->x)); \

Arguably this is wrong, because LP64 has sizeof(long) != 4. This ought
to be something like:

+ SEQ_printf(m, " .%-30s: %d\n", #x, (int)(rq->x)); \

> else \
> SEQ_printf(m, " .%-30s: %Ld\n", #x, (long long)(rq->x));\
> } while (0)"
>
> The result will be 4294967287 on 64-bit machines to print (long)(rq->x)
> while old type 'unsigned long' will print -9.
>
> And the other places that use its value will cast to int to return
> expected output, so we convert its type from 'unsigned int' to int.
>
> Signed-off-by: Yan Yan <[email protected]>
> ---
> kernel/sched/loadavg.c | 2 +-
> kernel/sched/sched.h | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c
> index 52c8f8226b0d..b9867495fe8b 100644
> --- a/kernel/sched/loadavg.c
> +++ b/kernel/sched/loadavg.c
> @@ -80,7 +80,7 @@ long calc_load_fold_active(struct rq *this_rq, long adjust)
> long nr_active, delta = 0;
>
> nr_active = this_rq->nr_running - adjust;
> - nr_active += (int)this_rq->nr_uninterruptible;
> + nr_active += this_rq->nr_uninterruptible;
>
> if (nr_active != this_rq->calc_load_active) {
> delta = nr_active - this_rq->calc_load_active;
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 060616944d7a..23c643948331 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1006,7 +1006,7 @@ struct rq {
> * one CPU and if it got migrated afterwards it may decrease
> * it on another CPU. Always updated under the runqueue lock:
> */
> - unsigned int nr_uninterruptible;
> + int nr_uninterruptible;

Bit meh on this; but I suppose since calc_load_fold_active() already had
an explicit cast, it won't make the 'but signed overflow is UB' crowd
more unhappy.