Messages in this thread Patch in this message | | | Date | Tue, 8 Jan 2008 23:15:07 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] system timer: fix crash in <100Hz system timer |
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On Sat, 5 Jan 2008 16:16:55 -0600 David Fries <david@fries.net> wrote:
> --- a/kernel/time.c > +++ b/kernel/time.c > @@ -565,7 +565,11 @@ EXPORT_SYMBOL(jiffies_to_timeval); > clock_t jiffies_to_clock_t(long x) > { > #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 > + #if HZ < USER_HZ > + return x * (USER_HZ / HZ); > + #else > return x / (HZ / USER_HZ); > + #endif > #else > u64 tmp = (u64)x * TICK_NSEC; > do_div(tmp, (NSEC_PER_SEC / USER_HZ)); > @@ -598,7 +602,12 @@ EXPORT_SYMBOL(clock_t_to_jiffies); > u64 jiffies_64_to_clock_t(u64 x) > { > #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 > - do_div(x, HZ / USER_HZ); > + #if HZ < USER_HZ > + x *= USER_HZ; > + do_div(x, HZ); > + #else > + do_div(x, HZ / USER_HZ); > + #endif > #else
Somwhat off-topic:
I guess HZ=USER_HZ is a not-uncommon case, and it's pretty silly calling do_div(x, 1) all the time. How about we optimise that case?
Perhaps there are other places...
--- a/kernel/time.c~speed-up-jiffies-conversion-functions-if-hz==user_hz +++ a/kernel/time.c @@ -618,8 +618,10 @@ u64 jiffies_64_to_clock_t(u64 x) # if HZ < USER_HZ x *= USER_HZ; do_div(x, HZ); -# else +# elif HZ > USER_HZ do_div(x, HZ / USER_HZ); +# else + /* Nothing to do */ # endif #else /* _
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