Messages in this thread | | | From | Arnd Bergmann <> | Date | Tue, 14 Nov 2017 21:18:33 +0100 | Subject | Re: [PATCH] [RFC] time: Make sure jiffies_to_msecs() preserves non-zero time periods |
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On Tue, Nov 14, 2017 at 6:36 PM, Geert Uytterhoeven <geert@linux-m68k.org> wrote: > For the common cases where 1000 is a multiple of HZ, or HZ is a multiple > of 1000, jiffies_to_msecs() never returns zero when passed a non-zero > time period. > > However, if HZ > 1000 and not an integer multiple of 1000 (e.g. 2001), > jiffies_to_msecs() may return zero for small non-zero time periods. > This may break code that relies on receiving back a non-zero value, e.g. > drivers/char/tpm/tpm2-cmd.c:tpm2_do_selftest().
For reference, there are exactly three platforms that allow HZ to be larger than 1000, and they specifically use HZ=1024: alpha, itanium and mips/decstation.
> With the fix above, this becomes a false positive. > Nevertheless, it may be a good idea to preinitialize rc anyway, but I > have no idea what's the correct value (else I would have sent a patch > to do so ;-).
I think changing the while() loop into do{}while() would be appropriate here.
Arnd
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