linux-kernel - Re: [PATCH] ARCv2: Additional trace IRQs to support locking correctness validator

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Date:	Tue, 12 Apr 2016 19:42:34 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Evgeny Voevodin <evgeny.voevodin@...el.com>
CC:	Sergey Samoylidi <sergey.n.samoylidi@...el.com>,
	<linux-snps-arc@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARCv2: Additional trace IRQs to support locking
 correctness validator

Hi Evgeny,

On Wednesday 23 March 2016 02:56 PM, Evgeny Voevodin wrote:
> Flags should be saved in the same format in which clri instruction saves
> them since they are passed directly to seti instruction over
> arch_local_save_flags/arch_local_irq_restore calls.
> Trace of all clri/seti assembly calls is added to support locking
> correctness validator properly.
> With this patch it is possible to use locking correctness framework which
> did stop itself due to incomplete support. Locking tests are also became
> available and work propely.

This is a nice patch !

> 
> Signed-off-by: Evgeny Voevodin <evgeny.voevodin@...el.com>
> ---
>  arch/arc/include/asm/irqflags-arcv2.h | 31 ++++++++++++++++++++++++++++++-
>  arch/arc/kernel/entry-arcv2.S         | 14 +++++++++++++-
>  2 files changed, 43 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arc/include/asm/irqflags-arcv2.h b/arch/arc/include/asm/irqflags-arcv2.h
> index 37c2f75..bb17044 100644
> --- a/arch/arc/include/asm/irqflags-arcv2.h
> +++ b/arch/arc/include/asm/irqflags-arcv2.h
> @@ -15,8 +15,13 @@
>  #define STATUS_AD_BIT	19   /* Disable Align chk: core supports non-aligned */
>  #define STATUS_IE_BIT	31
>  
> +/* status32 Bits stored on clri instruction */
> +#define CLRI_STATUS_IE_BIT	4
> +
>  #define STATUS_AD_MASK		(1<<STATUS_AD_BIT)
>  #define STATUS_IE_MASK		(1<<STATUS_IE_BIT)
> +#define CLRI_STATUS_E_MASK	(0xF)
> +#define CLRI_STATUS_IE_MASK	(1<<CLRI_STATUS_IE_BIT)
>  
>  #define AUX_USER_SP		0x00D
>  #define AUX_IRQ_CTRL		0x00E
> @@ -100,6 +105,9 @@ static inline long arch_local_save_flags(void)
>  	:
>  	: "memory");
>  
> +	temp = (1 << 5) |
> +		((!!(temp & STATUS_IE_MASK)) << CLRI_STATUS_IE_BIT) |
> +		(temp & CLRI_STATUS_E_MASK);
>  	return temp;
>  }
>  
> @@ -108,7 +116,7 @@ static inline long arch_local_save_flags(void)
>   */
>  static inline int arch_irqs_disabled_flags(unsigned long flags)
>  {
> -	return !(flags & (STATUS_IE_MASK));
> +	return !(flags & (CLRI_STATUS_IE_MASK));
>  }
>  
>  static inline int arch_irqs_disabled(void)
> @@ -128,11 +136,32 @@ static inline void arc_softirq_clear(int irq)
>  
>  #else
>  
> +#ifdef CONFIG_TRACE_IRQFLAGS
> +
> +.macro TRACE_ASM_IRQ_DISABLE
> +	bl	trace_hardirqs_off
> +.endm
> +
> +.macro TRACE_ASM_IRQ_ENABLE
> +	bl	trace_hardirqs_on
> +.endm
> +
> +#else
> +
> +.macro TRACE_ASM_IRQ_DISABLE
> +.endm
> +
> +.macro TRACE_ASM_IRQ_ENABLE
> +.endm
> +
> +#endif
>  .macro IRQ_DISABLE  scratch
>  	clri
> +	TRACE_ASM_IRQ_DISABLE
>  .endm
>  
>  .macro IRQ_ENABLE  scratch
> +	TRACE_ASM_IRQ_ENABLE
>  	seti
>  .endm
>  
> diff --git a/arch/arc/kernel/entry-arcv2.S b/arch/arc/kernel/entry-arcv2.S
> index c126460..24d9431 100644
> --- a/arch/arc/kernel/entry-arcv2.S
> +++ b/arch/arc/kernel/entry-arcv2.S
> @@ -69,8 +69,11 @@ ENTRY(handle_interrupt)
>  
>  	clri		; To make status32.IE agree with CPU internal state
>  
> -	lr  r0, [ICAUSE]
> +#ifdef CONFIG_TRACE_IRQFLAGS
> +	TRACE_ASM_IRQ_DISABLE
> +#endif
>  
> +	lr  r0, [ICAUSE]
>  	mov   blink, ret_from_exception
>  
>  	b.d  arch_do_IRQ
> @@ -173,6 +176,15 @@ END(EV_TLBProtV)
>  	lr	r10, [AUX_IRQ_ACT]
>  
>  	bmsk	r11, r10, 15	; AUX_IRQ_ACT.ACTIVE
> +#ifdef CONFIG_TRACE_IRQFLAGS
> +	push r0
> +	push r10
> +	push r11
> +	TRACE_ASM_IRQ_ENABLE
> +	pop r11
> +	pop r10
> +	pop r0
> +#endif
>  	breq	r11, 0, .Lexcept_ret	; No intr active, ret from Exception

Can we not call TRACE_ASM_IRQ_ENABLE right after .Lrestore_regs, before reading
any of these registers to avoid the push/pop dance. I don't see why it needs to be
done where u have placed it currently.

I will give it a spin at my end as well.

Thx,
-Vineet

>  
>  ;####### Return from Intr #######
>