Messages in this thread | | | Date | Tue, 6 Jul 2021 10:49:39 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH] s390/vfio-ap: do not use open locks during VFIO_GROUP_NOTIFY_SET_KVM notification |
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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
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