Messages in this thread | | | Subject | Re: [PATCH] s390/vfio-ap: do not use open locks during VFIO_GROUP_NOTIFY_SET_KVM notification | From | Tony Krowiak <> | Date | Tue, 6 Jul 2021 18:43:39 -0400 |
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On 7/6/21 9:49 AM, Jason Gunthorpe wrote: > On Tue, Jul 06, 2021 at 09:39:29AM -0400, Tony Krowiak wrote: >> >> On 7/5/21 10:13 AM, Jason Gunthorpe wrote: >>> On Thu, Jul 01, 2021 at 10:28:52AM -0400, Tony Krowiak wrote: >>> >>>>> I think Jason was talking about open coding locks in general. >>>> That may be so, but his comments were in support of his >>>> statement that the mutex + wait_queue did not resolve >>>> the issue reported vai the lockdep splat because it turned >>>> off lockdep. >>> Rgiht, if this used to be proper locks and lockdep complained then >>> whatever potential deadlock it found is not magically removed by going >>> to a wait_queue. It just removes the lockdep annotations that would >>> identify the issue early. >>> >>> This is why people should not open code locks, it completely defeats >>> lockdep. That alone is merit enough for this patch. >> When you use the phrase "open code locks", to what are you >> specifically referring? I am confused by the use of the phrase >> "open code" in this context because open coding, at least as >> I understand it, has to do with data analysis. > "open code" here means you write the algorithm of a standard lock in > your own functions instead of calling the standard library. > > Testing/setting the busy and sleeping on a wait_event is exactly a > standard lock. > > Ie if I write > > for (len = 0; str[len] != 0; len++) > ; > > Then I have open coded strlen() > > Jason
Thanks for the explanation.
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