Date: Fri, 1 Mar 2019 13:19:05 -0800 From: Mark Millard <marklmi@yahoo.com> To: Konstantin Belousov <kib@freebsd.org> Cc: Bruce Evans <brde@optusnet.com.au>, freebsd-hackers Hackers <freebsd-hackers@freebsd.org>, FreeBSD PowerPC ML <freebsd-ppc@freebsd.org> Subject: Re: powerpc64 head -r344018 stuck sleeping problems: th->th_scale * tc_delta(th) overflows unsigned 64 bits sometimes [patched failed] Message-ID: <87D6CBD5-AE55-4EC8-8797-D8A9DC3D5A5A@yahoo.com> In-Reply-To: <20190301194217.GB68879@kib.kiev.ua> References: <D3D7E9F4-9A5E-4320-B3C8-EC5CEF4A2764@yahoo.com> <20190228145542.GT2420@kib.kiev.ua> <20190228150811.GU2420@kib.kiev.ua> <962D78C3-65BE-40C1-BB50-A0088223C17B@yahoo.com> <28C2BB0A-3DAA-4D18-A317-49A8DD52778F@yahoo.com> <20190301112717.GW2420@kib.kiev.ua> <20190302043936.A4444@besplex.bde.org> <20190301194217.GB68879@kib.kiev.ua>
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On 2019-Mar-1, at 11:42, Konstantin Belousov <kib at freebsd.org> wrote:
> . . .
> +#ifdef _LP64
> + scale_bits = ffsl(scale);
> +#else
> + scale_bits = ffsll(scale);
> +#endif. . .
> + if (__predict_false(scale_bits + fls(delta) > 63)) {
The patch from yesterday uniformly used:
int
fls(int mask)
{
int bit;
if (mask == 0)
return (0);
for (bit = 1; mask != 1; bit++)
mask = (unsigned int)mask >> 1;
return (bit);
}
that looks for the most significant 1 bit.
The new patch uses in some places:
int
ffsl(long mask)
{
int bit;
if (mask == 0)
return (0);
for (bit = 1; !(mask & 1); bit++)
mask = (unsigned long)mask >> 1;
return (bit);
}
that looks for the least significant 1 bit. Similarly
for:
int
ffsll(long long mask)
{
int bit;
if (mask == 0)
return (0);
for (bit = 1; !(mask & 1); bit++)
mask = (unsigned long long)mask >> 1;
return (bit);
}
Was that deliberate?
===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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