Re: [RFC PATCH 1/9] Add #defs for paca->soft_enabled flags

[Nicholas Piggin]

On Tue, 26 Jul 2016 11:35:16 +0530
Madhavan Srinivasan  wrote:

> On Tuesday 26 July 2016 10:57 AM, Nicholas Piggin wrote:
> > On Mon, 25 Jul 2016 20:22:14 +0530
> > Madhavan Srinivasan  wrote:
> >  
> >> Two #defs LAZY_INTERRUPT_ENABLED and
> >> LAZY_INTERRUPT_DISABLED are added to be used
> >> when updating paca->soft_enabled.  
> > This is a very nice patchset, but can this not be a new name?  
> 
> Thanks, but idea is from ben :)
> Regarding the name, I looked at the initial patchset posted by
> paul and took the name from it :).


I did this quick hack for doing nmi watchdog using masked
decrementer interrupts instead of perf.

I think it should allow us to trip on hangs in
local_irq_and_pmu_disable() regions where the existing
one would not. Of course local atomics will not be usable
in the watchdog code, but that's more tractable than PMU
interrupts (or we just do our own private NMI watchdog
like other arch's do so we control everything -- sparc's
implementation is only 270 lines).

Let me know if you find it useful.

Thanks,
Nick


diff --git a/arch/Kconfig b/arch/Kconfig
index d794384..a307407 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -35,7 +35,7 @@ config HAVE_OPROFILE
 
 config OPROFILE_NMI_TIMER
def_bool y
-   depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI && !PPC64
+   depends on PERF_EVENTS && HAVE_PERF_EVENTS_NMI
 
 config KPROBES
bool "Kprobes"
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 01f7464..87a0816 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -130,6 +130,7 @@ config PPC
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_CBPF_JIT
select HAVE_ARCH_JUMP_LABEL
+   select HAVE_NMI
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_HAS_GCOV_PROFILE_ALL
select GENERIC_SMP_IDLE_THREAD
@@ -154,8 +155,6 @@ config PPC
select DCACHE_WORD_ACCESS if PPC64 && CPU_LITTLE_ENDIAN
select NO_BOOTMEM
select HAVE_GENERIC_RCU_GUP
-   select HAVE_PERF_EVENTS_NMI if PPC64
-   select HAVE_NMI if PERF_EVENTS
select EDAC_SUPPORT
select EDAC_ATOMIC_SCRUB
select ARCH_HAS_DMA_SET_COHERENT_MASK
diff --git a/arch/powerpc/include/asm/nmi.h b/arch/powerpc/include/asm/nmi.h
index ff1ccb3..90ab2bb 100644
--- a/arch/powerpc/include/asm/nmi.h
+++ b/arch/powerpc/include/asm/nmi.h
@@ -1,4 +1,8 @@
 #ifndef _ASM_NMI_H
 #define _ASM_NMI_H
 
+extern int nmi_enable(u64 period);
+extern void nmi_disable(void);
+extern void nmi_interrupt(struct pt_regs *regs);
+
 #endif /* _ASM_NMI_H */
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index 546540b..6b3b041 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -153,6 +153,9 @@ struct paca_struct {
u64 saved_msr;  /* MSR saved here by enter_rtas */
u16 trap_save;  /* Used when bad stack is encountered */
u8 soft_enabled;/* irq soft-enable flag */
+#ifdef CONFIG_HARDLOCKUP_DETECTOR
+   u8 nmi_enabled; /* generate nmis when soft-disabled */
+#endif
u8 irq_happened;/* irq happened while soft-disabled */
u8 io_sync; /* writel() needs spin_unlock sync */
u8 irq_work_pending;/* IRQ_WORK interrupt while 
soft-disable */
diff --git a/arch/powerpc/kernel/asm-offsets.c 
b/arch/powerpc/kernel/asm-offsets.c
index 9ea0955..4bf327d 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -190,6 +190,9 @@ int main(void)
DEFINE(PACAKBASE, offsetof(struct paca_struct, kernelbase));
DEFINE(PACAKMSR, offsetof(struct paca_struct, kernel_msr));
DEFINE(PACASOFTIRQEN, offsetof(struct paca_struct, soft_enabled));
+#ifdef CONFIG_HARDLOCKUP_DETECTOR
+   DEFINE(PACANMIENABLED, offsetof(struct paca_struct, nmi_enabled));
+#endif
DEFINE(PACAIRQHAPPENED, offsetof(struct paca_struct, irq_happened));
 #ifdef CONFIG_PPC_BOOK3S
DEFINE(PACACONTEXTID, offsetof(struct paca_struct, mm_ctx_id));
diff --git a/arch/powerpc/kernel/exceptions-64s.S 
b/arch/powerpc/kernel/exceptions-64s.S
index 4c94406..972f368 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -634,6 +634,8 @@ masked_##_H##interrupt: 
\
lis r10,0x7fff; \
ori r10,r10,0x; \
mtspr   SPRN_DEC,r10;   \
+   /* XXX: test nmi enabled and depend CONFIG_HARDLOCKUP_DETECTOR */ \
+   b   masked_decrementer_##_H##interrupt; \
b   2f; \
 1: cmpwi   r10,PACA_IRQ_DBELL; \
beq 2f; \
@@ -650,9 +652,21 @@ masked_##_H##interrupt:

Re: [RFC PATCH 1/9] Add #defs for paca->soft_enabled flags

[Nicholas Piggin]

On Tue, 26 Jul 2016 11:35:16 +0530
Madhavan Srinivasan  wrote:

> On Tuesday 26 July 2016 10:57 AM, Nicholas Piggin wrote:
> > On Mon, 25 Jul 2016 20:22:14 +0530
> > Madhavan Srinivasan  wrote:
> >  
> >> Two #defs LAZY_INTERRUPT_ENABLED and
> >> LAZY_INTERRUPT_DISABLED are added to be used
> >> when updating paca->soft_enabled.  
> > This is a very nice patchset, but can this not be a new name?  
> 
> Thanks, but idea is from ben :)
> Regarding the name, I looked at the initial patchset posted by
> paul and took the name from it :).
> 
> But will work on that, any suggestion for the name?

I don't have a strong preference. LAZY_* is not horrible itself,
it's just that softe variant is used elsewhere. I don't mind if
you rename softe to something else completely (although Ben might).
Allow me to apply the first coat of paint to the bikeshed:

irq_disable_level

IRQ_DISABLE_LEVEL_NONE
IRQ_DISABLE_LEVEL_LINUX
IRQ_DISABLE_LEVEL_PMU

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Re: [RFC PATCH 1/9] Add #defs for paca->soft_enabled flags

[Madhavan Srinivasan]

On Tuesday 26 July 2016 10:57 AM, Nicholas Piggin wrote:

On Mon, 25 Jul 2016 20:22:14 +0530
Madhavan Srinivasan  wrote:


Two #defs LAZY_INTERRUPT_ENABLED and
LAZY_INTERRUPT_DISABLED are added to be used
when updating paca->soft_enabled.

This is a very nice patchset, but can this not be a new name?


Thanks, but idea is from ben :)
Regarding the name, I looked at the initial patchset posted by
paul and took the name from it :).

But will work on that, any suggestion for the name?

Maddy


We use "soft enabled/disabled" everywhere for it. I think lazy
is an implementation detail anyway because some interrupts don't
cause a hard disable at all.

Thanks,
Nick



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Re: [RFC PATCH 1/9] Add #defs for paca->soft_enabled flags

[Nicholas Piggin]

On Mon, 25 Jul 2016 20:22:14 +0530
Madhavan Srinivasan  wrote:

> Two #defs LAZY_INTERRUPT_ENABLED and
> LAZY_INTERRUPT_DISABLED are added to be used
> when updating paca->soft_enabled.

This is a very nice patchset, but can this not be a new name?
We use "soft enabled/disabled" everywhere for it. I think lazy
is an implementation detail anyway because some interrupts don't
cause a hard disable at all.

Thanks,
Nick
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[RFC PATCH 1/9] Add #defs for paca->soft_enabled flags

[Madhavan Srinivasan]

Two #defs LAZY_INTERRUPT_ENABLED and
LAZY_INTERRUPT_DISABLED are added to be used
when updating paca->soft_enabled.

Signed-off-by: Madhavan Srinivasan 
---
-If the macro names looks not right, kindly suggest

 arch/powerpc/include/asm/hw_irq.h | 7 +++
 1 file changed, 7 insertions(+)

diff --git a/arch/powerpc/include/asm/hw_irq.h 
b/arch/powerpc/include/asm/hw_irq.h
index b59ac27a6b7d..e58c9d95050a 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -27,6 +27,13 @@
 #define PACA_IRQ_EE_EDGE   0x10 /* BookE only */
 #define PACA_IRQ_HMI   0x20
 
+/*
+ * flags for paca->soft_enabled
+ */
+#define LAZY_INTERRUPT_ENABLED 1
+#define LAZY_INTERRUPT_DISABLED0
+
+
 #endif /* CONFIG_PPC64 */
 
 #ifndef __ASSEMBLY__
-- 
2.7.4

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