Messages in this thread | | | Date | Mon, 07 Jan 2008 15:51:09 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] system timer: fix crash in <100Hz system timer |
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Andrew Morton wrote: >> >> diff --git a/include/linux/acct.h b/include/linux/acct.h >> index 302eb72..86b848d 100644 >> --- a/include/linux/acct.h >> +++ b/include/linux/acct.h >> @@ -173,7 +173,11 @@ typedef struct acct acct_t; >> static inline u32 jiffies_to_AHZ(unsigned long x) >> { >> #if (TICK_NSEC % (NSEC_PER_SEC / AHZ)) == 0 >> - return x / (HZ / AHZ); >> + #if HZ < AHZ >> + return x * (AHZ / HZ); >> + #else >> + return x / (HZ / AHZ); >> + #endif >> #else >> u64 tmp = (u64)x * TICK_NSEC; >> do_div(tmp, (NSEC_PER_SEC / AHZ)); >> diff --git a/kernel/time.c b/kernel/time.c >> index 09d3c45..23af26f 100644 >> --- 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 >> /* >> * There are better ways that don't overflow early, > > Alas, I get 100% rejects due to conflicting changes from Peter's > avoid-overflows-in-kernel-timec.patch. > > Peter, did that patch propagate this failure, or might it have happily > fixed it? >
My patch doesn't touch any of these functions, nor touches any code within 70 lines of this patch -- the last line touched is line 478 -- and doesn't touch linux/acct.h at all, so how could it cause a conflict?
But no, it doesn't fix this particular problem, even if using a similar technique might very well be a better way to do this kind of conversion.
-hpa
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