linux-kernel - Re: [PATCH RFC 1/2] m68k: Add tracirqs

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Message-ID: <86eea4de-2696-4485-9c16-cd3fbbd1aae6@yoseli.org>
Date: Wed, 23 Oct 2024 07:53:39 +0200
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: Michael Schmitz <schmitzmic@...il.com>,
 Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, rostedt@...dmis.org
Subject: Re: [PATCH RFC 1/2] m68k: Add tracirqs

Hi Michael,

On 23/10/2024 05:53, Michael Schmitz wrote:
> Jean-Michel,
> 
> thanks for your patches!
> 
> Am 21.10.2024 um 22:44 schrieb Jean-Michel Hautbois:
>> The TRACE_IRQFLAGS_SUPPORT requires the architecture to call
>> trace_hardirqs_off() when interrupts are disabled and
>> trace_hardirqs_on() when they are enabled.
>> Add those calls to do_IRQ function.
> 
> You will also have to add these calls to the three sites in arch/m68k/ 
> coldfire/head.S where interrupts are enabled or disabled.

Thanks for this ! I prepared a v2 with those calls added. I am wondering 
if my second patch is ok, I think it is not, could you please review it 
? There may already be something related to the stack in the assembly 
part useful to implement arch_stack_walk() in a different way ?
> 
> Here:
>> ENTRY(system_call)
>>         SAVE_ALL_SYS
>>         move    #0x2000,%sr             /* enable intrs again */
>>         GET_CURRENT(%d2)
> 
> and here:
>> ret_from_exception:
>>         move    #0x2700,%sr             /* disable intrs */
>>         btst    #5,%sp@(PT_OFF_SR)      /* check if returning to 
>> kernel */
>>         jeq     Luser_return            /* if so, skip resched, 
>> signals */
> 
> and here:
>> Lwork_to_do:
>>         movel   %a0@(TINFO_FLAGS),%d1   /* get thread_info->flags */
>>         move    #0x2000,%sr             /* enable intrs again */
>>         btst    #TIF_NEED_RESCHED,%d1
>>         jne     reschedule
> 
> There's one similar site in arch/m68k/kernel/head.S (ret_from_exception) 
> where interrupts are enabled that would need a similar change, if you 
> want to enable this for all m68k.

I won't be able to test it though ;-).
I see there are a few interrupts disabling in 
arch/m68k/include/asm/entry.h too ?

> 
> Registers %d0-%d5 and %a0-%a2 are saved on the stack at this point and 
> can be clobbered if need be.

I don't know if they need to be clobbered...

Thanks,
JM

> 
> Cheers,
> 
>      Michael
> 
> 
>>
>> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
>> ---
>>  arch/m68k/Kconfig      | 1 +
>>  arch/m68k/kernel/irq.c | 2 ++
>>  2 files changed, 3 insertions(+)
>>
>> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
>> index 
>> cc26df907bfe3c8143a931d259eceabb16af7411..ab3375475721fa63418c40d4ba6ac76679ebc77d 100644
>> --- a/arch/m68k/Kconfig
>> +++ b/arch/m68k/Kconfig
>> @@ -39,6 +39,7 @@ config M68K
>>      select OLD_SIGSUSPEND3
>>      select UACCESS_MEMCPY if !MMU
>>      select ZONE_DMA
>> +    select TRACE_IRQFLAGS_SUPPORT
>>
>>  config CPU_BIG_ENDIAN
>>      def_bool y
>> diff --git a/arch/m68k/kernel/irq.c b/arch/m68k/kernel/irq.c
>> index 
>> 9ab4f550342e5de11c528f55781432675ffd66bf..74cf60ebbc4bca51f3caa4046dbd2bdb02355711 100644
>> --- a/arch/m68k/kernel/irq.c
>> +++ b/arch/m68k/kernel/irq.c
>> @@ -21,9 +21,11 @@ asmlinkage void do_IRQ(int irq, struct pt_regs *regs)
>>  {
>>      struct pt_regs *oldregs = set_irq_regs(regs);
>>
>> +    trace_hardirqs_off();
>>      irq_enter();
>>      generic_handle_irq(irq);
>>      irq_exit();
>> +    trace_hardirqs_on();
>>
>>      set_irq_regs(oldregs);
>>  }
>>