Messages in this thread | | | Date | Sun, 28 Apr 2024 12:13:11 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 1/3] x86/tsc: Use div64_ul instead of do_div() |
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On April 28, 2024 10:31:16 AM PDT, Jules Irenge <jbi.octave@gmail.com> wrote: >do_div() truncates a u64 divisor to 32 bit. >This can lead to non-zero being truncated to zero for division. > >Fix coccinelle warning >WARNING: do_div() does a 64-by-32 division, please consider using div64_ul instead > >Signed-off-by: Jules Irenge <jbi.octave@gmail.com> >--- > arch/x86/kernel/tsc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c >index 5a69a49acc96..2da37f33dd17 100644 >--- a/arch/x86/kernel/tsc.c >+++ b/arch/x86/kernel/tsc.c >@@ -484,7 +484,7 @@ static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin) > > /* Calculate the PIT value */ > delta = t2 - t1; >- do_div(delta, ms); >+ div64_ul(delta, ms); > return delta; > } >
Are you sure this is not a false positive? This is a *much* more expensive operation on 32 bits.
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