Messages in this thread | | | Date | Sat, 19 Nov 2011 10:26:58 +0100 | From | Marco Stornelli <> | Subject | Re: [PATCH] include/log2.h: Fix rounddown_pow_of_two(1) |
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Il 18/11/2011 00:05, Andrew Morton ha scritto: > On Wed, 16 Nov 2011 14:56:06 -0500 > Andrei Warkentin<andreiw@vmware.com> wrote: > >> 1 is a power of two, therefore rounddown_pow_of_two(1) should return 1. It does >> in case the argument is a variable but in case it's a constant it behaves >> wrong and returns 0. Probably nobody ever did it so this was never noticed, >> however net/drivers/vmxnet3 with latest GCC does and breaks on unicpu systems. >> >> This is similar to Rolf's patch to roundup_pow_of_two(1). >> >> Cc: Rolf Eike Beer<eike-kernel@sf-tec.de> >> Cc: opensuse-kernel@opensuse.org >> Reviewed-by: Jesper Juhl<jj@chaosbits.net> >> Signed-off-by: Andrei Warkentin<andreiw@vmware.com> >> --- >> include/linux/log2.h | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/include/linux/log2.h b/include/linux/log2.h >> index 25b8086..ccda848 100644 >> --- a/include/linux/log2.h >> +++ b/include/linux/log2.h >> @@ -185,7 +185,7 @@ unsigned long __rounddown_pow_of_two(unsigned long n) >> #define rounddown_pow_of_two(n) \ >> ( \ >> __builtin_constant_p(n) ? ( \ >> - (n == 1) ? 0 : \ >> + (n == 1) ? 1 : \ >> (1UL<< ilog2(n))) : \ >> __rounddown_pow_of_two(n) \ >> ) > > I assume that nobody has gone off and checked whether all current > callers will survive this change. If they had, they'd have looked in > drivers/char/ramoops.c and seen: > > rounddown_pow_of_two(pdata->mem_size); > rounddown_pow_of_two(pdata->record_size); > > These operations are no-ops. It should be > > pdata->mem_size = rounddown_pow_of_two(pdata->mem_size); > pdata->record_size = rounddown_pow_of_two(pdata->record_size); > > Marco or Sergio: please fix, test and send it over sometime?
Ok, I'll look at it.
Marco
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