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Message-ID: <20241023052719.4c43b7af@rorschach.local.home>
Date: Wed, 23 Oct 2024 05:27:19 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
Cc: Michael Schmitz <schmitzmic@...il.com>, Geert Uytterhoeven
<geert@...ux-m68k.org>, linux-m68k@...ts.linux-m68k.org,
linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/2] m68k: Add tracirqs
On Wed, 23 Oct 2024 10:59:42 +0200
Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org> wrote:
>
> Sadly, not that straightforward.
> I have this patch right now:
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index b2a3093af677..fc4a2d124514 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -41,6 +41,7 @@ config M68K
> select ZONE_DMA
> select ARCH_SUPPORTS_RT
> select IRQ_FORCED_THREADING
> + select TRACE_IRQFLAGS_SUPPORT
>
> config CPU_BIG_ENDIAN
> def_bool y
> diff --git a/arch/m68k/coldfire/entry.S b/arch/m68k/coldfire/entry.S
> index 4ea08336e2fb..fbdc4404f29e 100644
> --- a/arch/m68k/coldfire/entry.S
> +++ b/arch/m68k/coldfire/entry.S
> @@ -57,6 +57,9 @@ enosys:
> ENTRY(system_call)
> SAVE_ALL_SYS
> move #0x2000,%sr /* enable intrs again */
> +#ifdef CONFIG_TRACE_IRQFLAGS
> + jbsr trace_hardirqs_on
> +#endif
Note, the trace_hardirqs_on/off() needs to be done when interrupts are
disabled. That is:
__local_irq_disable();
trace_hardirqs_off();
[..]
trace_hardirqs_on();
__local_irq_enable();
I don't know the m68k assembly, but from the comments it looks like you
are calling these with interrupts enabled.
-- Steve
> GET_CURRENT(%d2)
>
> cmpl #NR_syscalls,%d0
> @@ -99,6 +102,9 @@ ENTRY(system_call)
> addql #4,%sp
>
> ret_from_exception:
> +#ifdef CONFIG_TRACE_IRQFLAGS
> + jbsr trace_hardirqs_off
> +#endif
> move #0x2700,%sr /* disable intrs */
> btst #5,%sp@(PT_OFF_SR) /* check if returning to kernel */
> jeq Luser_return /* if so, skip resched, signals */
> @@ -140,6 +146,9 @@ Lreturn:
> Lwork_to_do:
> movel %a0@(TINFO_FLAGS),%d1 /* get thread_info->flags */
> move #0x2000,%sr /* enable intrs again */
> +#ifdef CONFIG_TRACE_IRQFLAGS
> + jbsr trace_hardirqs_on
> +#endif
> btst #TIF_NEED_RESCHED,%d1
> jne reschedule
>
> But it fails when init is called:
> [ 5.313000] Run /bin/bash as init process
> [ 5.314000] with arguments:
> [ 5.315000] /bin/bash
> [ 5.316000] with environment:
> [ 5.317000] HOME=/
> [ 5.318000] TERM=linux
> [ 5.684000] Kernel panic - not syncing: Attempted to kill init!
> exitcode=0x0000000b
> [ 5.684000] CPU: 0 UID: 0 PID: 1 Comm: bash Not tainted
> 6.12.0-rc4-00049-g4393ca34ead3 #364
> [ 5.684000] Stack from 41a03e18:
> [ 5.684000] 41a03e18 41540187 41540187 0000000a ffffffff
> 415a8fb4 4140dd90 41416588
> [ 5.684000] 41540187 4140d5de 4102ba84 4100b19c 4100b1a8
> 00000000 41a38000 4102ba3a
> [ 5.684000] 41a03ea0 4100c34a 4150e87e 0000000b 0000000b
> 41a03f80 0000000a 41a3c0d4
> [ 5.684000] 41a02000 400004d8 41a08000 4102ba3a 4102ba84
> 00000000 00000000 000000ff
> [ 5.684000] 00000000 00000000 41a03ef4 4100cb82 0000000b
> 0000000b 41a03f80 41a03f6c
> [ 5.684000] 41016cd2 0000000b 41a03f6c 0000001d 00000026
> 0000048c ffffffff 00000006
> [ 5.684000] Call Trace: [<4140dd90>] _printk+0x0/0x18
> [ 5.684000] [<41416588>] dump_stack+0xc/0x10
> [ 5.684000] [<4140d5de>] panic+0xf2/0x2d4
> [ 5.684000] [<4102ba84>] preempt_count_sub+0x0/0x2e
> [ 5.684000] [<4100b19c>] arch_local_irq_enable+0x0/0xc
> [ 5.684000] [<4100b1a8>] arch_irqs_disabled+0x0/0x10
> [ 5.684000] [<4102ba3a>] preempt_count_add+0x0/0x1e
> [ 5.684000] [<4100c34a>] do_exit+0x266/0x930
> [ 5.684000] [<4102ba3a>] preempt_count_add+0x0/0x1e
> [ 5.684000] [<4102ba84>] preempt_count_sub+0x0/0x2e
> [ 5.684000] [<4100cb82>] do_group_exit+0x26/0xba
> [ 5.684000] [<41016cd2>] get_signal+0x60e/0x76c
> [ 5.684000] [<410044e8>] test_ti_thread_flag+0x0/0x14
> [ 5.684000] [<4102ba94>] preempt_count_sub+0x10/0x2e
> [ 5.684000] [<41004b68>] do_notify_resume+0x3a/0x4c6
> [ 5.684000] [<41015d52>] force_sig_fault_to_task+0x32/0x3e
> [ 5.684000] [<41015d72>] force_sig_fault+0x14/0x1a
> [ 5.684000] [<41005606>] buserr_c+0x9a/0x188
> [ 5.684000] [<410065fc>] Lsignal_return+0x14/0x24
> [ 5.684000] [<410065de>] Lwork_to_do+0xe/0x18
> [ 5.684000]
> [ 5.684000] ---[ end Kernel panic - not syncing: Attempted to kill
> init! exitcode=0x0000000b ]---
>
>
> JM
>
> >>
> >>>
> >>> 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...
> >
> > I meant to say that if you need registers to prepare function arguments
> > for trace_irqs_on/off() on the stack, these can be used. But that may
> > not be necessary in this case.
> >
> > Cheers,
> >
> > Michael
> >
> >
> >>
> >> 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);
> >>>> }
> >>>>
> >>
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