The documentation of msecs_to_jiffies() says:
* - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
*
* - 'too large' values [that would result in larger than
* MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
But when you pass in e.g. MAX_JIFFY_OFFSET + 1000 for HZ = 1000 it will not
return MAX_JIFFY_OFFSET, but the bigger value. This makes sure that the value
returned from this function can never be bigger than MAX_JIFFY_OFFSET. Also
use DIV_ROUND_UP() in one place where that is open coded.
Signed-off-by: Rolf Eike Beer <[email protected]>
---
kernel/time.c | 8 +++++---
1 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/time.c b/kernel/time.c
index 8e8dc6d..1ccec53 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -433,6 +433,7 @@ EXPORT_SYMBOL(ns_to_timeval);
*/
unsigned long msecs_to_jiffies(const unsigned int m)
{
+ unsigned long r;
/*
* Negative value, means infinite timeout:
*/
@@ -445,7 +446,7 @@ unsigned long msecs_to_jiffies(const unsigned int m)
* round multiple of HZ, divide with the factor between them,
* but round upwards:
*/
- return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
+ r = DIV_ROUND_UP(m, MSEC_PER_SEC / HZ);
#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
/*
* HZ is larger than 1000, and HZ is a nice round multiple of
@@ -457,7 +458,7 @@ unsigned long msecs_to_jiffies(const unsigned int m)
if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
return MAX_JIFFY_OFFSET;
- return m * (HZ / MSEC_PER_SEC);
+ r = m * (HZ / MSEC_PER_SEC);
#else
/*
* Generic case - multiply, round and divide. But first
@@ -467,9 +468,10 @@ unsigned long msecs_to_jiffies(const unsigned int m)
if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
return MAX_JIFFY_OFFSET;
- return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
+ r = (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
>> MSEC_TO_HZ_SHR32;
#endif
+ return min_t(unsigned long, r, MAX_JIFFY_OFFSET);
}
EXPORT_SYMBOL(msecs_to_jiffies);
--
1.7.3.2
On Tue, 29 Mar 2011, Rolf Eike Beer wrote:
> The documentation of msecs_to_jiffies() says:
>
> * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
> *
> * - 'too large' values [that would result in larger than
> * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
>
> But when you pass in e.g. MAX_JIFFY_OFFSET + 1000 for HZ = 1000 it will not
> return MAX_JIFFY_OFFSET, but the bigger value. This makes sure that the value
That's only true for 32 bit.
> returned from this function can never be bigger than MAX_JIFFY_OFFSET. Also
> use DIV_ROUND_UP() in one place where that is open coded.
> unsigned long msecs_to_jiffies(const unsigned int m)
> {
> + unsigned long r;
> /*
> * Negative value, means infinite timeout:
> */
> @@ -445,7 +446,7 @@ unsigned long msecs_to_jiffies(const unsigned int m)
> * round multiple of HZ, divide with the factor between them,
> * but round upwards:
> */
> - return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
> + r = DIV_ROUND_UP(m, MSEC_PER_SEC / HZ);
> #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
> /*
> * HZ is larger than 1000, and HZ is a nice round multiple of
> @@ -457,7 +458,7 @@ unsigned long msecs_to_jiffies(const unsigned int m)
> if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
> return MAX_JIFFY_OFFSET;
>
> - return m * (HZ / MSEC_PER_SEC);
> + r = m * (HZ / MSEC_PER_SEC);
For this case the jiffies_to_msec() check should be sufficient.
> #else
> /*
> * Generic case - multiply, round and divide. But first
> @@ -467,9 +468,10 @@ unsigned long msecs_to_jiffies(const unsigned int m)
> if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
> return MAX_JIFFY_OFFSET;
Hmm, this check is silly. MUL32 is chosen, so that we cannot overflow.
> - return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
> + r = (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
>> MSEC_TO_HZ_SHR32;
> #endif
> + return min_t(unsigned long, r, MAX_JIFFY_OFFSET);
> }
> EXPORT_SYMBOL(msecs_to_jiffies);
I start to wonder whether we really need these three variants or
whether we just could go with that MUL/SHIFT based implementation and
a final check for MAX_JIFFY_OFFSET. That would boil down to:
unsigned long msecs_to_jiffies(const unsigned int m)
{
u64 res = (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32;
return min_t(unsigned long, (unsigned long)res, MAX_JIFFY_OFFSET);
}
That'd avoid the whole division and msecs_to_jiffies() is not really a
high precision function.
Thanks,
tglx
Am Dienstag, 29. M?rz 2011, 21:42:59 schrieb Thomas Gleixner:
> On Tue, 29 Mar 2011, Rolf Eike Beer wrote:
> > @@ -467,9 +468,10 @@ unsigned long msecs_to_jiffies(const unsigned int m)
> >
> > if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
> >
> > return MAX_JIFFY_OFFSET;
>
> Hmm, this check is silly. MUL32 is chosen, so that we cannot overflow.
IMHO the second part of the check should be enough, no? If m is greater than
j2m(MAX) then it's irrelevant what's up else, it's too big. Period.
Eike
Am Dienstag, 29. M?rz 2011, 21:42:59 schrieb Thomas Gleixner:
> On Tue, 29 Mar 2011, Rolf Eike Beer wrote:
> > The documentation of msecs_to_jiffies() says:
> > * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET)
> > *
> > * - 'too large' values [that would result in larger than
> > * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too.
> >
> > But when you pass in e.g. MAX_JIFFY_OFFSET + 1000 for HZ = 1000 it will
> > not return MAX_JIFFY_OFFSET, but the bigger value. This makes sure that
> > the value
>
> That's only true for 32 bit.
>
> > returned from this function can never be bigger than MAX_JIFFY_OFFSET.
> > Also use DIV_ROUND_UP() in one place where that is open coded.
> >
> > unsigned long msecs_to_jiffies(const unsigned int m)
> > {
> >
> > + unsigned long r;
> >
> > /*
> >
> > * Negative value, means infinite timeout:
> > */
> >
> > @@ -445,7 +446,7 @@ unsigned long msecs_to_jiffies(const unsigned int m)
> >
> > * round multiple of HZ, divide with the factor between them,
> > * but round upwards:
> > */
> >
> > - return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
> > + r = DIV_ROUND_UP(m, MSEC_PER_SEC / HZ);
> >
> > #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
> >
> > /*
> >
> > * HZ is larger than 1000, and HZ is a nice round multiple of
> >
> > @@ -457,7 +458,7 @@ unsigned long msecs_to_jiffies(const unsigned int m)
> >
> > if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
> >
> > return MAX_JIFFY_OFFSET;
> >
> > - return m * (HZ / MSEC_PER_SEC);
> > + r = m * (HZ / MSEC_PER_SEC);
>
> For this case the jiffies_to_msec() check should be sufficient.
>
> > #else
> >
> > /*
> >
> > * Generic case - multiply, round and divide. But first
> >
> > @@ -467,9 +468,10 @@ unsigned long msecs_to_jiffies(const unsigned int
> > m)
> >
> > if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
> >
> > return MAX_JIFFY_OFFSET;
>
> Hmm, this check is silly. MUL32 is chosen, so that we cannot overflow.
>
> > - return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
> > + r = (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
> >
> >> MSEC_TO_HZ_SHR32;
> >
> > #endif
> >
> > + return min_t(unsigned long, r, MAX_JIFFY_OFFSET);
> >
> > }
> > EXPORT_SYMBOL(msecs_to_jiffies);
>
> I start to wonder whether we really need these three variants or
> whether we just could go with that MUL/SHIFT based implementation and
> a final check for MAX_JIFFY_OFFSET. That would boil down to:
>
> unsigned long msecs_to_jiffies(const unsigned int m)
> {
> u64 res = (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32;
>
> return min_t(unsigned long, (unsigned long)res, MAX_JIFFY_OFFSET);
> }
>
> That'd avoid the whole division and msecs_to_jiffies() is not really a
> high precision function.
Ping? Is anyone going to either take my patch or do it's own reworking of that
function?
Eike