bit fields && data tearing

Paul E. McKenney paulmck at linux.vnet.ibm.com
Sat Sep 6 06:09:26 EST 2014


On Fri, Sep 05, 2014 at 03:24:35PM -0400, Peter Hurley wrote:
> On 09/05/2014 03:05 PM, Paul E. McKenney wrote:
> > On Fri, Sep 05, 2014 at 02:50:31PM -0400, Peter Hurley wrote:
> >> On 09/05/2014 02:09 PM, Paul E. McKenney wrote:
> 
> [cut]
> 
> >>> ------------------------------------------------------------------------
> >>>
> >>> documentation: Record limitations of bitfields and small variables
> >>>
> >>> This commit documents the fact that it is not safe to use bitfields as
> >>> shared variables in synchronization algorithms.  It also documents that
> >>> CPUs must provide one-byte and two-byte load and store instructions
> >>                    ^
> >>                 atomic
> > 
> > Here you meant non-atomic?  My guess is that you are referring to the
> > fact that you could emulate a one-byte store on pre-EV56 Alpha CPUs
> > using the ll and sc atomic-read-modify-write instructions, correct?
> 
> Yes, that's what I meant. I must be tired and am misreading the commit
> message, or misinterpreting it's meaning.

Very good, got it!

							Thanx, Paul



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