Re: [PATCH 00/36] cpuidle,rcu: Cleanup the mess
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On Tue, Jun 14, 2022 at 06:58:30PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 14, 2022 at 12:19:29PM +0100, Mark Rutland wrote:
> > On Wed, Jun 08, 2022 at 04:27:23PM +0200, Peter Zijlstra wrote:
> > > Hi All! (omg so many)
> >
> > Hi Peter,
> >
> > Sorry for the delay; my plate has also been rather full recently. I'm
> > beginning
> > to page this in now.
>
> No worries; we all have too much to do ;-)
>
> > > These here few patches mostly clear out the utter mess that is cpuidle vs
> > > rcuidle.
> > >
> > > At the end of the ride there's only 2 real RCU_NONIDLE() users left
> > >
> > > arch/arm64/kernel/suspend.c:
> > > RCU_NONIDLE(__cpu_suspend_exit());
> > > drivers/perf/arm_pmu.c: RCU_NONIDLE(armpmu_start(event,
> > > PERF_EF_RELOAD));
> >
> > The latter of these is necessary because apparently PM notifiers are called
> > with RCU not watching. Is that still the case today (or at the end of this
> > series)? If so, that feels like fertile land for more issues (yaey...). If
> > not,
> > we should be able to drop this.
>
> That should be fixed; fingers crossed :-)
Cool; I'll try to give that a spin when I'm sat next to some relevant hardware.
:)
> > > kernel/cfi.c: RCU_NONIDLE({
> > >
> > > (the CFI one is likely dead in the kCFI rewrite) and there's only a hand
> > > full
> > > of trace_.*_rcuidle() left:
> > >
> > > kernel/trace/trace_preemptirq.c:
> > > trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
> > > kernel/trace/trace_preemptirq.c:
> > > trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
> > > kernel/trace/trace_preemptirq.c:
> > > trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
> > > kernel/trace/trace_preemptirq.c:
> > > trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
> > > kernel/trace/trace_preemptirq.c:
> > > trace_preempt_enable_rcuidle(a0, a1);
> > > kernel/trace/trace_preemptirq.c:
> > > trace_preempt_disable_rcuidle(a0, a1);
> > >
> > > All of them are in 'deprecated' code that is unused for GENERIC_ENTRY.
> > I think those are also unused on arm64 too?
> >
> > If not, I can go attack that.
>
> My grep spots:
>
> arch/arm64/kernel/entry-common.c: trace_hardirqs_on();
> arch/arm64/include/asm/daifflags.h: trace_hardirqs_off();
> arch/arm64/include/asm/daifflags.h: trace_hardirqs_off();
Ah; I hadn't realised those used trace_.*_rcuidle() behind the scenes.
That affects local_irq_{enable,disable,restore}() too (which is what the
daifflags.h bits are emulating), and also the generic entry code's
irqentry_exit().
So it feels to me like we should be fixing those more generally? e.g. say that
with a new STRICT_ENTRY[_RCU], we can only call trace_hardirqs_{on,off}() with
RCU watching, and alter the definition of those?
> The _on thing should be replaced with something like:
>
> trace_hardirqs_on_prepare();
> lockdep_hardirqs_on_prepare();
> instrumentation_end();
> rcu_irq_exit();
> lockdep_hardirqs_on(CALLER_ADDR0);
>
> (as I think you know, since you have some of that already). And
> something similar for the _off thing, but with _off_finish().
Sure; I knew that was necessary for the outermost parts of entry (and I think
that's all handled), I just hadn't realised that trace_hardirqs_{on,off} did
the rcuidle thing in the middle.
It'd be nice to not have to open-code the whole sequence everywhere for the
portions which run after entry and are instrumentable, so (as above) I reckon
we want to make trace_hardirqs_{on,off}() not do the rcuidle part
unnecessarily (which IIUC is an end-goal anyway)?
> > > I've touched a
Re: [PATCH 00/36] cpuidle,rcu: Cleanup the mess
arndb.de>, ulli.kr...@googlemail.com, vgu...@kernel.org,
linux-...@vger.kernel.org, j...@joshtriplett.org, rost...@goodmis.org,
r...@vger.kernel.org, b...@alien8.de, bc...@quicinc.com,
tsbog...@alpha.franken.de, linux-par...@vger.kernel.org, sudeep.ho...@arm.com,
shawn...@kernel.org, da...@davemloft.net, dal...@libc.org, t...@atomide.com,
amakha...@vmware.com, bjorn.anders...@linaro.org, h...@zytor.com,
sparcli...@vger.kernel.org, linux-hexa...@vger.kernel.org,
linux-ri...@lists.infradead.org, anton.iva...@cambridgegreys.com,
jo...@southpole.se, yury.no...@gmail.com, rich...@nod.at, x...@kernel.org,
li...@armlinux.org.uk, mi...@redhat.com, a...@eecs.berkeley.edu,
paul...@kernel.org, h...@linux.ibm.com, stefan.kristians...@saunalahti.fi,
openr...@lists.librecores.org, paul.walms...@sifive.com,
linux-te...@vger.kernel.org, namhy...@kernel.org,
andriy.shevche...@linux.intel.com, jpoim...@kernel.org, jgr...@suse.com,
mon...@monstr.eu, linux-m...@vger.kernel.org, pal...@dabbelt.com, anup@brainfa
ult.org, i...@jurassic.park.msu.ru, johan...@sipsolutions.net,
linuxppc-dev@lists.ozlabs.org
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On Tue, Jun 14, 2022 at 12:19:29PM +0100, Mark Rutland wrote:
> On Wed, Jun 08, 2022 at 04:27:23PM +0200, Peter Zijlstra wrote:
> > Hi All! (omg so many)
>
> Hi Peter,
>
> Sorry for the delay; my plate has also been rather full recently. I'm
> beginning
> to page this in now.
No worries; we all have too much to do ;-)
> > These here few patches mostly clear out the utter mess that is cpuidle vs
> > rcuidle.
> >
> > At the end of the ride there's only 2 real RCU_NONIDLE() users left
> >
> > arch/arm64/kernel/suspend.c:RCU_NONIDLE(__cpu_suspend_exit());
> > drivers/perf/arm_pmu.c: RCU_NONIDLE(armpmu_start(event,
> > PERF_EF_RELOAD));
>
> The latter of these is necessary because apparently PM notifiers are called
> with RCU not watching. Is that still the case today (or at the end of this
> series)? If so, that feels like fertile land for more issues (yaey...). If
> not,
> we should be able to drop this.
That should be fixed; fingers crossed :-)
> > kernel/cfi.c: RCU_NONIDLE({
> >
> > (the CFI one is likely dead in the kCFI rewrite) and there's only a hand
> > full
> > of trace_.*_rcuidle() left:
> >
> > kernel/trace/trace_preemptirq.c:
> > trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
> > kernel/trace/trace_preemptirq.c:
> > trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
> > kernel/trace/trace_preemptirq.c:
> > trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
> > kernel/trace/trace_preemptirq.c:
> > trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
> > kernel/trace/trace_preemptirq.c:
> > trace_preempt_enable_rcuidle(a0, a1);
> > kernel/trace/trace_preemptirq.c:
> > trace_preempt_disable_rcuidle(a0, a1);
> >
> > All of them are in 'deprecated' code that is unused for GENERIC_ENTRY.
>
> I think those are also unused on arm64 too?
>
> If not, I can go attack that.
My grep spots:
arch/arm64/kernel/entry-common.c: trace_hardirqs_on();
arch/arm64/include/asm/daifflags.h: trace_hardirqs_off();
arch/arm64/include/asm/daifflags.h: trace_hardirqs_off();
The _on thing should be replaced with something like:
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare();
instrumentation_end();
rcu_irq_exit();
lockdep_hardirqs_on(CALLER_ADDR0);
(as I think you know, since you have some of that already). And
something similar for the _off thing, but with _off_finish().
> > I've touched a _lot_ of code that I can't test and likely broken some of it
> > :/
> > In particular, the whole ARM cpuidle stuff was quite involved with OMAP
> > being
> > the absolute 'winner'.
> >
> > I'm hoping Mark can help me sort the remaining ARM64 bits as he moves that
> > to
> > GENERIC_ENTRY.
>
> Moving to GENERIC_ENTRY as a whole is going to take a tonne of work
> (refactoring both arm64 and the generic portion to be more amenable to each
> other), but we can certainly move closer to that for the bits that matter
> here.
I know ... been there etc.. :-)
> Maybe we want a STRICT_ENTRY option to get rid of all the deprecated stuff
> that
> we can select regardless of GENERIC_ENTRY to make that easier.
Possible yeah.
> > I've also got a note that says ARM64 can probably do a WFE based
> > idle state and employ TIF_POLLING_NRFLAG to avoid some IPIs.
>
> Possibly; I'm not sure how much of a win that'll be given that by default
> we'll
> have a ~10KHz WFE wakeup from the timer, but we could take a peek.
Ohh.. I didn't know it woke up *that* often. I just know Will made use
of it in things like smp_cond_load_relaxed() which would be somewhat
similar to a
Re: [PATCH 00/36] cpuidle,rcu: Cleanup the mess
arndb.de>, ulli.kr...@googlemail.com, vgu...@kernel.org,
linux-...@vger.kernel.org, j...@joshtriplett.org, rost...@goodmis.org,
r...@vger.kernel.org, b...@alien8.de, bc...@quicinc.com,
tsbog...@alpha.franken.de, linux-par...@vger.kernel.org, sudeep.ho...@arm.com,
shawn...@kernel.org, da...@davemloft.net, dal...@libc.org, t...@atomide.com,
amakha...@vmware.com, bjorn.anders...@linaro.org, h...@zytor.com,
sparcli...@vger.kernel.org, linux-hexa...@vger.kernel.org,
linux-ri...@lists.infradead.org, anton.iva...@cambridgegreys.com,
jo...@southpole.se, yury.no...@gmail.com, rich...@nod.at, x...@kernel.org,
li...@armlinux.org.uk, mi...@redhat.com, a...@eecs.berkeley.edu,
paul...@kernel.org, h...@linux.ibm.com, stefan.kristians...@saunalahti.fi,
openr...@lists.librecores.org, paul.walms...@sifive.com,
linux-te...@vger.kernel.org, namhy...@kernel.org,
andriy.shevche...@linux.intel.com, jpoim...@kernel.org, jgr...@suse.com,
mon...@monstr.eu, linux-m...@vger.kernel.org, pal...@dabbelt.com, anup@brainfa
ult.org, i...@jurassic.park.msu.ru, johan...@sipsolutions.net,
linuxppc-dev@lists.ozlabs.org
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Sender: "Linuxppc-dev"
On Wed, Jun 08, 2022 at 04:27:23PM +0200, Peter Zijlstra wrote:
> Hi All! (omg so many)
Hi Peter,
Sorry for the delay; my plate has also been rather full recently. I'm beginning
to page this in now.
> These here few patches mostly clear out the utter mess that is cpuidle vs
> rcuidle.
>
> At the end of the ride there's only 2 real RCU_NONIDLE() users left
>
> arch/arm64/kernel/suspend.c:RCU_NONIDLE(__cpu_suspend_exit());
> drivers/perf/arm_pmu.c: RCU_NONIDLE(armpmu_start(event,
> PERF_EF_RELOAD));
The latter of these is necessary because apparently PM notifiers are called
with RCU not watching. Is that still the case today (or at the end of this
series)? If so, that feels like fertile land for more issues (yaey...). If not,
we should be able to drop this.
I can go dig into that some more.
> kernel/cfi.c: RCU_NONIDLE({
>
> (the CFI one is likely dead in the kCFI rewrite) and there's only a hand full
> of trace_.*_rcuidle() left:
>
> kernel/trace/trace_preemptirq.c:
> trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
> kernel/trace/trace_preemptirq.c:
> trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
> kernel/trace/trace_preemptirq.c:
> trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
> kernel/trace/trace_preemptirq.c:
> trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
> kernel/trace/trace_preemptirq.c:
> trace_preempt_enable_rcuidle(a0, a1);
> kernel/trace/trace_preemptirq.c:
> trace_preempt_disable_rcuidle(a0, a1);
>
> All of them are in 'deprecated' code that is unused for GENERIC_ENTRY.
I think those are also unused on arm64 too?
If not, I can go attack that.
> I've touched a _lot_ of code that I can't test and likely broken some of it :/
> In particular, the whole ARM cpuidle stuff was quite involved with OMAP being
> the absolute 'winner'.
>
> I'm hoping Mark can help me sort the remaining ARM64 bits as he moves that to
> GENERIC_ENTRY.
Moving to GENERIC_ENTRY as a whole is going to take a tonne of work
(refactoring both arm64 and the generic portion to be more amenable to each
other), but we can certainly move closer to that for the bits that matter here.
Maybe we want a STRICT_ENTRY option to get rid of all the deprecated stuff that
we can select regardless of GENERIC_ENTRY to make that easier.
> I've also got a note that says ARM64 can probably do a WFE based
> idle state and employ TIF_POLLING_NRFLAG to avoid some IPIs.
Possibly; I'm not sure how much of a win that'll be given that by default we'll
have a ~10KHz WFE wakeup from the timer, but we could take a peek.
Thanks,
Mark.
[PATCH 00/36] cpuidle,rcu: Cleanup the mess
, Arnd Bergmann , ulli.kr...@googlemail.com, vgu...@kernel.org,
linux-...@vger.kernel.org, j...@joshtriplett.org, rost...@goodmis.org,
r...@vger.kernel.org, b...@alien8.de, bc...@quicinc.com,
tsbog...@alpha.franken.de, linux-par...@vger.kernel.org, sudeep.ho...@arm.com,
shawn...@kernel.org, da...@davemloft.net, dal...@libc.org, t...@atomide.com,
amakha...@vmware.com, bjorn.anders...@linaro.org, h...@zytor.com,
sparcli...@vger.kernel.org, linux-hexa...@vger.kernel.org,
linux-ri...@lists.infradead.org, anton.iva...@cambridgegreys.com,
jo...@southpole.se, yury.no...@gmail.com, rich...@nod.at, x...@kernel.org,
li...@armlinux.org.uk, mi...@redhat.com, a...@eecs.berkeley.edu,
paul...@kernel.org, h...@linux.ibm.com, stefan.kristians...@saunalahti.fi,
openr...@lists.librecores.org, paul.walms...@sifive.com,
linux-te...@vger.kernel.org, namhy...@kernel.org,
andriy.shevche...@linux.intel.com, jpoim...@kernel.org, jgr...@suse.com,
mon...@monstr.eu, linux-m...@vger.kernel.org, palmer@dab
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johan...@sipsolutions.net, linuxppc-dev@lists.ozlabs.org
Errors-To: linuxppc-dev-bounces+archive=mail-archive@lists.ozlabs.org
Sender: "Linuxppc-dev"
Hi All! (omg so many)
These here few patches mostly clear out the utter mess that is cpuidle vs
rcuidle.
At the end of the ride there's only 2 real RCU_NONIDLE() users left
arch/arm64/kernel/suspend.c:RCU_NONIDLE(__cpu_suspend_exit());
drivers/perf/arm_pmu.c: RCU_NONIDLE(armpmu_start(event,
PERF_EF_RELOAD));
kernel/cfi.c: RCU_NONIDLE({
(the CFI one is likely dead in the kCFI rewrite) and there's only a hand full
of trace_.*_rcuidle() left:
kernel/trace/trace_preemptirq.c:
trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
kernel/trace/trace_preemptirq.c:
trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
kernel/trace/trace_preemptirq.c:
trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr);
kernel/trace/trace_preemptirq.c:
trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr);
kernel/trace/trace_preemptirq.c:
trace_preempt_enable_rcuidle(a0, a1);
kernel/trace/trace_preemptirq.c:
trace_preempt_disable_rcuidle(a0, a1);
All of them are in 'deprecated' code that is unused for GENERIC_ENTRY.
I've touched a _lot_ of code that I can't test and likely broken some of it :/
In particular, the whole ARM cpuidle stuff was quite involved with OMAP being
the absolute 'winner'.
I'm hoping Mark can help me sort the remaining ARM64 bits as he moves that to
GENERIC_ENTRY. I've also got a note that says ARM64 can probably do a WFE based
idle state and employ TIF_POLLING_NRFLAG to avoid some IPIs.
---
arch/alpha/kernel/process.c |1
arch/alpha/kernel/vmlinux.lds.S |1
arch/arc/kernel/process.c|3 +
arch/arc/kernel/vmlinux.lds.S|1
arch/arm/include/asm/vmlinux.lds.h |1
arch/arm/kernel/process.c|1
arch/arm/kernel/smp.c|6 +--
arch/arm/mach-gemini/board-dt.c |3 +
arch/arm/mach-imx/cpuidle-imx6q.c|4 +-
arch/arm/mach-imx/cpuidle-imx6sx.c |5 ++
arch/arm/mach-omap2/cpuidle34xx.c| 16
arch/arm/mach-omap2/cpuidle44xx.c| 29 +--
arch/arm/mach-omap2/pm.h |2 -
arch/arm/mach-omap2/pm34xx.c | 14 +--
arch/arm/mach-omap2/powerdomain.c| 10 ++---
arch/arm64/kernel/idle.c |1
arch/arm64/kernel/smp.c |4 +-
arch/arm64/kernel/vmlinux.lds.S |1
arch/csky/kernel/process.c |1
arch/csky/kernel/smp.c |2 -
arch/csky/kernel/vmlinux.lds.S |1
arch/hexagon/kernel/process.c|1
arch/hexagon/kernel/vmlinux.lds.S|1
arch/ia64/kernel/process.c |1
arch/ia64/kernel/vmlinux.lds.S |1
arch/loongarch/kernel/vmlinux.lds.S |1
arch/m68k/kernel/vmlinux-nommu.lds |1
arch/m68k/kernel/vmlinux-std.lds |1
arch/m68k/kernel/vmlinux-sun3.lds|1
arch/microblaze/kernel/process.c |1
arch/microblaze/kernel/vmlinux.lds.S |1
arch/mips/kernel/idle.c |8 +---
arch/mips/kernel/vmlinux.lds.S |1
arch/nios2/kernel/process.c |1
arch/nios2/kernel/vmlinux.lds.S |1
arch/openrisc/kernel/process.c |1
arch/openrisc/kernel/vmlinux.lds.S |1
arch/parisc/kernel/process.c |2 -
arch/parisc/kernel/vmlinux.lds.S |1
arch/powerpc/kernel/idle.c |5 +-
arch/powerpc/kernel/vmlinux.lds.S|1
arch/riscv/kernel/process.c |1
arch/riscv/kernel/vmlinux-xip.lds.S |1
arch/riscv/kernel/vmlinux.lds.S |1
arch/s390/kernel/idle.c |1
arch/s390/kernel/vmlinux.lds.S |1
