Messages in this thread | | | Date | Thu, 11 Aug 2016 23:26:30 +0000 (UTC) | From | Mathieu Desnoyers <> | Subject | Re: [RFC PATCH v7 7/7] Restartable sequences: self-tests |
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----- On Jul 24, 2016, at 2:01 PM, Dave Watson davejwatson@fb.com wrote:
>>> +static inline __attribute__((always_inline)) >>> +bool rseq_finish(struct rseq_lock *rlock, >>> + intptr_t *p, intptr_t to_write, >>> + struct rseq_state start_value) > >>> This ABI looks like it will work fine for our use case. I don't think it >>> has been mentioned yet, but we may still need multiple asm blocks >>> for differing numbers of writes. For example, an array-based freelist push: > >>> void push(void *obj) { >>> if (index < maxlen) { >>> freelist[index++] = obj; >>> } >>> } > >>> would be more efficiently implemented with a two-write rseq_finish: > >>> rseq_finish2(&freelist[index], obj, // first write >>> &index, index + 1, // second write >>> ...); > >> Would pairing one rseq_start with two rseq_finish do the trick >> there ? > > Yes, two rseq_finish works, as long as the extra rseq management overhead > is not substantial.
I've added a commit implementing rseq_finish2() in my rseq volatile dev branch. You can fetch it at:
https://github.com/compudj/linux-percpu-dev/tree/rseq-fallback
I also have a separate test and benchmark tree in addition to the kernel selftests here:
https://github.com/compudj/rseq-test
I named the first write a "speculative" write, and the second write the "final" write.
Would you like to extend the test cases to cover your intended use-case ?
Thanks,
Mathieu
-- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
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