Messages in this thread | | | Date | Sat, 1 Dec 2007 13:33:59 +0000 | From | Alan Cox <> | Subject | Re: [PATCH] Avoid overflows in kernel/time.c |
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On Sat, 1 Dec 2007 13:20:47 +0000 Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> On Sat, 1 Dec 2007 01:33:33 +0100 > Adrian Bunk <bunk@kernel.org> wrote: > > > On Thu, Nov 29, 2007 at 04:19:51PM -0800, H. Peter Anvin wrote: > > > When the conversion factor between jiffies and milli- or microseconds > > > is not a single multiply or divide, as for the case of HZ == 300, we > > > currently do a multiply followed by a divide. The intervening > > > result, however, is subject to overflows, especially since the > > > fraction is not simplified (for HZ == 300, we multiply by 300 and > > > divide by 1000). > > >... > > > kernel/Makefile | 8 +++ > > > kernel/time.c | 29 +++++++++--- > > > kernel/timeconst.bc | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++ > > > 3 files changed, 152 insertions(+), 8 deletions(-) > > > create mode 100644 kernel/timeconst.bc > > >... > > > > I have read the hep text, but are the advantages of HZ == 300 really > > visible or was this more theoretical? > > Its visibile for people doing PAL media processing and TV sync work.
Wake up Alan - NTSC for 300HZ, PAL is OK at 250HZ setting.
Alan
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