Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread peterz
On Mon, Sep 21, 2020 at 09:27:57PM +0200, Thomas Gleixner wrote: > On Mon, Sep 21 2020 at 09:24, Linus Torvalds wrote: > > On Mon, Sep 21, 2020 at 12:39 AM Thomas Gleixner wrote: > >> > >> If a task is migrated to a different CPU then the mapping address will > >> change which will explode in colo

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread peterz
On Mon, Sep 21, 2020 at 09:27:57PM +0200, Thomas Gleixner wrote: > Alternatively this could of course be solved with per CPU page tables > which will come around some day anyway I fear. Previously (with PTI) we looked at making the entire kernel map per-CPU, and that takes a 2K copy on switch_mm()

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread Thomas Gleixner
On Wed, Sep 23 2020 at 12:19, peterz wrote: > On Mon, Sep 21, 2020 at 09:27:57PM +0200, Thomas Gleixner wrote: >> Alternatively this could of course be solved with per CPU page tables >> which will come around some day anyway I fear. > > Previously (with PTI) we looked at making the entire kernel m

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread Thomas Gleixner
On Wed, Sep 23 2020 at 10:40, peterz wrote: > Right, so I'm concerned. migrate_disable() wrecks pretty much all > Real-Time scheduler theory we have, and PREEMPRT_RT bringing it in is > somewhat ironic. It's even more ironic that the approach of PREEMPT_RT has been 'pragmatic ignorance of theory'

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread Thomas Gleixner
On Mon, Sep 21 2020 at 21:27, Thomas Gleixner wrote: > On Mon, Sep 21 2020 at 09:24, Linus Torvalds wrote: >> On Mon, Sep 21, 2020 at 12:39 AM Thomas Gleixner wrote: >> Maybe we really *could* call this new kmap functionality something >> like "kmap_percpu()" (or maybe "local" is good enough), and

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread Steven Rostedt
On Wed, 23 Sep 2020 10:40:32 +0200 pet...@infradead.org wrote: > However, with migrate_disable() we can have each task preempted in a > migrate_disable() region, worse we can stack them all on the _same_ CPU > (super ridiculous odds, sure). And then we end up only able to run one > task, with the

Re: [PATCH v5 4/6] dt-bindings: dw-apb-ictl: support hierarchy irq domain

2020-09-23 Thread Rob Herring
On Fri, 18 Sep 2020 19:22:00 +0800, Zhen Lei wrote: > Add support to use dw-apb-ictl as primary interrupt controller. > > Signed-off-by: Zhen Lei > --- > .../bindings/interrupt-controller/snps,dw-apb-ictl.txt | 14 > +- > 1 file changed, 13 insertions(+), 1 deletion(-) > Revie

Re: [PATCH v5 5/6] dt-bindings: dw-apb-ictl: convert to json-schema

2020-09-23 Thread Rob Herring
On Fri, Sep 18, 2020 at 07:22:01PM +0800, Zhen Lei wrote: > Convert the Synopsys DesignWare APB interrupt controller (dw_apb_ictl) > binding to DT schema format using json-schema. > > Signed-off-by: Zhen Lei > --- > .../interrupt-controller/snps,dw-apb-ictl.txt | 43 - > .../int

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread Thomas Gleixner
On Wed, Sep 23 2020 at 11:52, Steven Rostedt wrote: > On Wed, 23 Sep 2020 10:40:32 +0200 > pet...@infradead.org wrote: > >> However, with migrate_disable() we can have each task preempted in a >> migrate_disable() region, worse we can stack them all on the _same_ CPU >> (super ridiculous odds, sure

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread Steven Rostedt
On Wed, 23 Sep 2020 22:55:54 +0200 Thomas Gleixner wrote: > > Perhaps make migrate_disable() an anonymous local_lock()? > > > > This should lower the SHC in theory, if you can't have stacked migrate > > disables on the same CPU. > > I'm pretty sure this ends up in locking hell pretty fast and

Re: [PATCH v5 5/6] dt-bindings: dw-apb-ictl: convert to json-schema

2020-09-23 Thread Leizhen (ThunderTown)
On 2020/9/24 4:49, Rob Herring wrote: > On Fri, Sep 18, 2020 at 07:22:01PM +0800, Zhen Lei wrote: >> Convert the Synopsys DesignWare APB interrupt controller (dw_apb_ictl) >> binding to DT schema format using json-schema. >> >> Signed-off-by: Zhen Lei >> --- >> .../interrupt-controller/snps,dw

Re: [PATCH v5 5/6] dt-bindings: dw-apb-ictl: convert to json-schema

2020-09-23 Thread Leizhen (ThunderTown)
On 2020/9/24 11:26, Leizhen (ThunderTown) wrote: > > > On 2020/9/24 4:49, Rob Herring wrote: >> On Fri, Sep 18, 2020 at 07:22:01PM +0800, Zhen Lei wrote: >>> Convert the Synopsys DesignWare APB interrupt controller (dw_apb_ictl) >>> binding to DT schema format using json-schema. >>> >>> Signed-

ARC: allmodconfig: Error: inappropriate arguments for opcode 'mpyd'

2020-09-23 Thread Naresh Kamboju
arc:allmodconfig build failed with gcc-8, gcc-9 and gcc-10 on Linus's mainline tree. Build log: make -sk KBUILD_BUILD_USER=TuxBuild -C/linux ARCH=arc CROSS_COMPILE=arc-elf32- HOSTCC=gcc CC="sccache arc-elf32-gcc" O=build allmodconfig make -sk KBUILD_BUILD_USER=TuxBuild -C/linux -j16

Re: [patch RFC 00/15] mm/highmem: Provide a preemptible variant of kmap_atomic & friends

2020-09-23 Thread Thomas Gleixner
On Wed, Sep 23 2020 at 17:12, Steven Rostedt wrote: > On Wed, 23 Sep 2020 22:55:54 +0200 > Then scratch the idea of having anonymous local_lock() and just bring > local_lock in directly? Then have a kmap local lock, which would only > block those that need to do a kmap. That's still going to end u