2014-04-21 13:40:42

by Chen Gang

Subject: [PATCH] kernel/power/hibernate.c: be sure of 'start' is not bigger than 'stop'

For do_div(), it need 'u64' type, which means the outside must be sure
of 'start' is not bigger than 'stop', or it will report warning.

The related warning (with allmodconfig for unicore32):

CC kernel/power/hibernate.o
kernel/power/hibernate.c: In function ?swsusp_show_speed?:
kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast

Signed-off-by: Chen Gang <[email protected]>
---
kernel/power/hibernate.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index f4f2073..0dec9b7 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -228,12 +228,17 @@ static void platform_recover(int platform_mode)
void swsusp_show_speed(struct timeval *start, struct timeval *stop,
unsigned nr_pages, char *msg)
{
- s64 elapsed_centisecs64;
+ u64 elapsed_centisecs64;
int centisecs;
int k;
int kps;

elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
+ if ((s64)elapsed_centisecs64 < 0) {
+ printk(KERN_ERR "PM: stop: %llu < start %llu\n",
+ timeval_to_ns(stop), timeval_to_ns(start));
+ return;
+ }
do_div(elapsed_centisecs64, NSEC_PER_SEC / 100);
centisecs = elapsed_centisecs64;
if (centisecs == 0)
--
1.9.2.459.g68773ac

2014-04-21 20:09:35

by Pavel Machek

Subject: Re: [PATCH] kernel/power/hibernate.c: be sure of 'start' is not bigger than 'stop'

On Mon 2014-04-21 21:40:27, Chen Gang wrote:
> For do_div(), it need 'u64' type, which means the outside must be sure
> of 'start' is not bigger than 'stop', or it will report warning.
>
> The related warning (with allmodconfig for unicore32):
>
> CC kernel/power/hibernate.o
> kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
> kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast
>
> Signed-off-by: Chen Gang <[email protected]>

> {
> - s64 elapsed_centisecs64;
> + u64 elapsed_centisecs64;
> int centisecs;
> int k;
> int kps;
>
> elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
> + if ((s64)elapsed_centisecs64 < 0) {
> + printk(KERN_ERR "PM: stop: %llu < start %llu\n",
> + timeval_to_ns(stop), timeval_to_ns(start));
> + return;
> + }
> do_div(elapsed_centisecs64, NSEC_PER_SEC / 100);
> centisecs = elapsed_centisecs64;
> if (centisecs == 0)

Quite a lot of code to shut up warning in mostly debugging
function... is there alternative method of shutting it up? Have you
seen < 0 values in wild? Is it worth handing that situation?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

2014-04-21 20:26:54

by Rafael J. Wysocki

Subject: Re: [PATCH] kernel/power/hibernate.c: be sure of 'start' is not bigger than 'stop'

On Monday, April 21, 2014 10:09:30 PM Pavel Machek wrote:
> On Mon 2014-04-21 21:40:27, Chen Gang wrote:
> > For do_div(), it need 'u64' type, which means the outside must be sure
> > of 'start' is not bigger than 'stop', or it will report warning.
> >
> > The related warning (with allmodconfig for unicore32):
> >
> > CC kernel/power/hibernate.o
> > kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
> > kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast
> >
> > Signed-off-by: Chen Gang <[email protected]>
>
> > {
> > - s64 elapsed_centisecs64;
> > + u64 elapsed_centisecs64;
> > int centisecs;
> > int k;
> > int kps;
> >
> > elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
> > + if ((s64)elapsed_centisecs64 < 0) {
> > + printk(KERN_ERR "PM: stop: %llu < start %llu\n",
> > + timeval_to_ns(stop), timeval_to_ns(start));
> > + return;
> > + }
> > do_div(elapsed_centisecs64, NSEC_PER_SEC / 100);
> > centisecs = elapsed_centisecs64;
> > if (centisecs == 0)
>
> Quite a lot of code to shut up warning in mostly debugging
> function... is there alternative method of shutting it up? Have you
> seen < 0 values in wild?

No, I don't think so. This is a purely theoretical problem that never
happens in practice, because all of the callers do the right thing.

Rafael

2014-04-22 00:58:42

by Chen Gang

Subject: Re: [PATCH] kernel/power/hibernate.c: be sure of 'start' is not bigger than 'stop'

On 04/22/2014 04:43 AM, Rafael J. Wysocki wrote:
> On Monday, April 21, 2014 10:09:30 PM Pavel Machek wrote:
>> On Mon 2014-04-21 21:40:27, Chen Gang wrote:
>>> For do_div(), it need 'u64' type, which means the outside must be sure
>>> of 'start' is not bigger than 'stop', or it will report warning.
>>>
>>> The related warning (with allmodconfig for unicore32):
>>>
>>> CC kernel/power/hibernate.o
>>> kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
>>> kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast
>>>
>>> Signed-off-by: Chen Gang <[email protected]>
>>
>>> {
>>> - s64 elapsed_centisecs64;
>>> + u64 elapsed_centisecs64;
>>> int centisecs;
>>> int k;
>>> int kps;
>>>
>>> elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
>>> + if ((s64)elapsed_centisecs64 < 0) {
>>> + printk(KERN_ERR "PM: stop: %llu < start %llu\n",
>>> + timeval_to_ns(stop), timeval_to_ns(start));
>>> + return;
>>> + }
>>> do_div(elapsed_centisecs64, NSEC_PER_SEC / 100);
>>> centisecs = elapsed_centisecs64;
>>> if (centisecs == 0)
>>
>> Quite a lot of code to shut up warning in mostly debugging
>> function... is there alternative method of shutting it up? Have you
>> seen < 0 values in wild?
>
> No, I don't think so. This is a purely theoretical problem that never
> happens in practice, because all of the callers do the right thing.
>
> Rafael
>

OK, it sounds fine to me, I shall send patch v2 for it.

Thanks.
--
Chen Gang

Open, share, and attitude like air, water, and life which God blessed