From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leon Romanovsky Subject: Re: [RFC] libibverbs IB device hotplug support Date: Thu, 2 Mar 2017 15:22:58 +0200 Message-ID: <20170302132258.GC9525@mtr-leonro.local> References: <20170301001023.GA3001@phlsvsds.ph.intel.com> <2807E5FD2F6FDA4886F6618EAC48510E67C5CA68@CRSMSX101.amr.corp.intel.com> <20170301230743.GC2820@obsidianresearch.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Sr1nOIr3CvdE5hEN" Return-path: Content-Disposition: inline In-Reply-To: <20170301230743.GC2820-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: "Weiny, Ira" , Alex Rosenbaum , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Yishai Hadas List-Id: linux-rdma@vger.kernel.org --Sr1nOIr3CvdE5hEN Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 --Sr1nOIr3CvdE5hEN Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkhr/r4Op1/04yqaB5GN7iDZyWKcFAli4HLIACgkQ5GN7iDZy WKexpRAAjwarY3GE97WLiu341MZjm4SR3UTyHC3IbC1TyEl7O8JS/g7eDfOwmFUl BolIZ10omkQbgJvbzygV9i7L0q+bRz7Hc7Trmyn4Or6U8FTAEXkK/F6qbvxh4wwB wAew+U6CxnwfOfgdw4GQzVqZFNEDJjs0Lo6ZP8PxJc1Za0itKQOdiq6QS/cXu5BN KfBeyQATJNXTfn8TaF8/NGh+u60Lk4tzzpIgDs3jr6/KnUGPTybqdhidQk2mleCg 1zrkd1cTgayXderxvVCVyNwA29QcBE0JBvkCaoLs0pnbkX+xmXiUcM5wXVlzCz8I sXviPJwLh0p2lux/rdrDh/VSG8VXn/kqOQ0k/T7sH3ofwVfWubFCFieCLsNRo1cE iWnLbI+c8YYKcttni2kSBrq469HfeAGq5i7+yw0s6wGwMQn2qxJmM7OSQUgIn2mo g71w+p3/3rBR//QyxUD3PUw473iovHguTKzl3RuXc4iUJEHZGPMxqMvtL3vOyBZv 66tYc4CHEYpb9QRMjQuwPhLqhAewzH33yo5u/BLDHAHv2cRp/C3/owJzf9HVcfLh UtpZGYq52ru9Ng2Rk8hWhW2WPyaHsTukV3THGQvsQW/JwEy7xB8SGss50fH6djC+ LxBo8jZpdeTgweqyJHerydfhUd62etplflt0L0EcFRtGO/i0bNA= =waBK -----END PGP SIGNATURE----- --Sr1nOIr3CvdE5hEN-- -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html