On Wed, Mar 01, 2017 at 04:07:43PM -0700, Jason Gunthorpe wrote: > On Wed, Mar 01, 2017 at 10:15:31PM +0000, Weiny, Ira wrote: > > > On the call we discussed that today there is no 'incarnation' > > > value exposed for the uverbs%. You suggested an optimization by > > > using the cdev's file creation timestamp as option for libibverbs > > > to understand that the driver did or did-not restart since mapping > > > of that ibv_device. > > Not the cdev, read the timestamp from /sys/class/infiniband/mlx4_0/hca_type > > > > Main pitfalls with this is if system time is being modified (admin > > > or ntp/ptp). In the rare case that we have a hoplug event and time > > > is rewinded we can accidentally reach a very hard debugging > > > exercise. > > You are only using it for direct equality comparision, so someone > would have to roll back the clock and hotplug the driver at the exact > same nano-second resolution timestamp. That is deeply unlikely to ever > happen by accident. Jason, I think that we are over engineering here, but it can occur with NTP clock hopping. Thanks > > Jason
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