Re: [PATCH 2/3] iommu/iova: don't disable preempt around this_cpu_ptr()

2017-06-28 Thread Joerg Roedel
On Wed, Jun 28, 2017 at 11:31:55AM +0200, Sebastian Andrzej Siewior wrote: > It really does. The spin_lock() does disable preemption but this is not > the problem. The thing is that the preempt_disable() is superfluous and > it hurts Preempt-RT (and this is how I noticed it). Also the > get_cpu_ptr

Re: [PATCH 2/3] iommu/iova: don't disable preempt around this_cpu_ptr()

2017-06-28 Thread Sebastian Andrzej Siewior
On 2017-06-28 11:22:05 [+0200], Joerg Roedel wrote: > On Tue, Jun 27, 2017 at 06:16:47PM +0200, Sebastian Andrzej Siewior wrote: > > Commit 583248e6620a ("iommu/iova: Disable preemption around use of > > this_cpu_ptr()") disables preemption while accessing a per-CPU variable. > > This does keep loc

Re: [PATCH 2/3] iommu/iova: don't disable preempt around this_cpu_ptr()

2017-06-28 Thread Joerg Roedel
On Tue, Jun 27, 2017 at 06:16:47PM +0200, Sebastian Andrzej Siewior wrote: > Commit 583248e6620a ("iommu/iova: Disable preemption around use of > this_cpu_ptr()") disables preemption while accessing a per-CPU variable. > This does keep lockdep quiet. However I don't see the point why it is > bad if

[PATCH 2/3] iommu/iova: don't disable preempt around this_cpu_ptr()

2017-06-27 Thread Sebastian Andrzej Siewior
Commit 583248e6620a ("iommu/iova: Disable preemption around use of this_cpu_ptr()") disables preemption while accessing a per-CPU variable. This does keep lockdep quiet. However I don't see the point why it is bad if we get migrated after its access to another CPU. __iova_rcache_insert() and __iova