Messages in this thread | | | Date | Mon, 16 Nov 2020 15:53:09 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 01/13] seqnum_ops: Introduce Sequence Number Ops |
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On Fri, Nov 13, 2020 at 10:46:03AM -0700, Shuah Khan wrote:
> +Increment interface > +------------------- > + > +Increments sequence number and returns the new value. :: > + > + seqnum32_inc_return() --> (u32) atomic_inc_return(seqnum) > + seqnum64_inc_return() --> (u64) atomic64_inc_return(seqnum)
Did you think about the ordering?
> +Fetch interface > +--------------- > + > +Fetched and returns current sequence number value. :: > + > + seqnum32_fetch() --> (u32) atomic_add_return(0, seqnum) > + seqnum64_fetch() --> (u64) atomic64_add_return(0, seqnum)
That's horrible. Please explain how that is not broken garbage.
Per the fact that it is atomic, nothing prevents the counter being incremented concurrently. There is no such thing as a 'current' sequence number.
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