On Sun, 15 May, at 10:14:39AM, Yuyang Du wrote: > Hi Matt, > > Thanks for Ccing me. > > I am indeed interested, because I recently encountered an rq clock > issue, which is that the clock jumps about 200ms when I was > experimenting the "flat util hierarchy" patches, which really annoyed > me, and I had to stop to figure out what is wrong (but haven't yet > figured out ;)) > > First, this patchset does not solve my problem, but never mind, by > reviewing your patches, I have some comments: Thanks for the review. One gap that this patch series doesn't address is that some callers of update_rq_clock() do not pin rq->lock, which makes the diagnostic checks useless in that case.
I plan on handling that next, but I wanted to get this series out as soon as possible for review. > On Thu, May 12, 2016 at 08:49:53PM +0100, Matt Fleming wrote: > > > > - rq->clock_skip_update = 0; > > + /* Clear ACT, preserve everything else */ > > + rq->clock_update_flags ^= RQCF_ACT_SKIP; > > The comment says "Clear ACT", but this is really xor, and I am not sure > this is even what you want. Urgh, you're right. I'm not sure what I was thinking when I wrote that. > In addition, would it be simpler to do this? > > update_rq_clock() > if (flags & RQCF_ACT_SKIP) > flags <<= 1; /* effective skip is an update */ > return; > > flags = RQCF_UPDATED; No because if someone calls rq_clock() immediately after __schedule(), or even immediately after we clear RQCF_ACT_SKIP in __schedule(), we should trigger a warning since the clock has not actually been updated.
