Messages in this thread | | | Date | Wed, 5 Nov 2008 11:20:06 -0500 (EST) | From | Alan Stern <> | Subject | Re: [PATCH 1/2] Add round_jiffies_up and related routines |
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On Wed, 5 Nov 2008, Tejun Heo wrote:
> Alan Stern wrote: > > This patch (as1158) adds round_jiffies_up() and friends. These > > routines work like the analogous round_jiffies() functions, except > > that they will never round down. > > > > The new routines will be useful for timeouts where we don't care > > exactly when the timer expires, provided it doesn't expire too soon. > > > > Signed-off-by: Alan Stern <stern@rowland.harvard.edu> > > Heh... I have exactly the same patches but mines were named > round_up_jiffies().
To an American, "round_up_jiffies" sounds like something a cowboy might do. :-)
I haven't bothered to look throughout the kernel to see where round_jiffies_up() could be used. Have you done this?
> > + unsigned long j0 = jiffies; > > + > > + barrier(); /* Prevent the compiler from aliasing j0 and jiffies */ > > + return round_jiffies_common(j + j0, cpu, false) - j0; > > jiffies is volatile. No need for explicit barrier,
I didn't realize that. Good, it makes things easier.
> but this part is > necessary for correct operation as if jiffies go up by two the > calculation will wrap and the returned value will be very large. I > think this fix deserves a separate patch and proper explanation.
How about if I remove the barrier() call? Should this new code still go in a separate patch?
Alan Stern
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