From: peterz@infradead.org
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-kernel@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
Subject: Re: [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state
Date: Wed, 19 Aug 2020 17:39:49 +0200 [thread overview]
Message-ID: <20200819153949.GO35926@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200819153250.GF2674@hirez.programming.kicks-ass.net>
On Wed, Aug 19, 2020 at 05:32:50PM +0200, peterz@infradead.org wrote:
> On Wed, Aug 19, 2020 at 08:39:13PM +1000, Alexey Kardashevskiy wrote:
>
> > > or current upstream?
> >
> > The upstream 18445bf405cb (13 hours old) also shows the problem. Yours
> > 1/2 still fixes it.
>
> Afaict that just reduces the window.
>
> Isn't the problem that:
>
> arch/powerpc/kernel/exceptions-64e.S
>
> START_EXCEPTION(perfmon);
> NORMAL_EXCEPTION_PROLOG(0x260, BOOKE_INTERRUPT_PERFORMANCE_MONITOR,
> PROLOG_ADDITION_NONE)
> EXCEPTION_COMMON(0x260)
> INTS_DISABLE
> # RECONCILE_IRQ_STATE
> # TRACE_DISABLE_INTS
> # TRACE_WITH_FRAME_BUFFER(trace_hardirqs_off)
> #
> # but we haven't done nmi_enter() yet... whoopsy
>
> CHECK_NAPPING()
> addi r3,r1,STACK_FRAME_OVERHEAD
> bl performance_monitor_exception
> # perf_irq()
> # perf_event_interrupt
> # __perf_event_interrupt
> # nmi_enter()
>
>
>
> That is, afaict your entry code is buggered.
That is, patch 1/2 doesn't change the case:
local_irq_enable()
trace_hardirqs_on()
<NMI>
trace_hardirqs_off()
...
if (regs_irqs_disabled(regs)) // false
trace_hardirqs_on();
</NMI>
raw_local_irq_enable()
Where local_irq_enable() has done trace_hardirqs_on() and the NMI hits
and undoes it, but doesn't re-do it because the hardware state is still
disabled.
What's supposed to happen is:
<NMI>
nmi_enter()
trace_hardirqs_off() // no-op, because in_nmi() (or previously because lockdep_off())
...
</NMI>
prev parent reply other threads:[~2020-08-19 15:44 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 10:56 [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Nicholas Piggin
2020-07-23 10:56 ` [PATCH 2/2] lockdep: warn on redundant or incorrect irq state changes Nicholas Piggin
2020-07-24 2:57 ` kernel test robot
2020-08-04 10:00 ` Alexey Kardashevskiy
2020-07-23 11:40 ` [PATCH 1/2] lockdep: improve current->(hard|soft)irqs_enabled synchronisation with actual irq state Peter Zijlstra
2020-07-23 13:11 ` Nicholas Piggin
2020-07-23 14:59 ` Peter Zijlstra
2020-07-23 16:20 ` Nicholas Piggin
2020-07-24 4:16 ` Alexey Kardashevskiy
2020-07-24 5:59 ` Nicholas Piggin
2020-07-26 7:40 ` Alexey Kardashevskiy
2020-07-24 6:16 ` Athira Rajeev
2020-07-24 2:19 ` kernel test robot
2020-07-24 3:15 ` kernel test robot
2020-07-25 20:26 ` Peter Zijlstra
2020-07-26 4:14 ` Nicholas Piggin
2020-07-26 11:59 ` peterz
2020-07-26 12:11 ` peterz
2020-07-28 11:22 ` Nicholas Piggin
2020-08-07 11:11 ` peterz
2020-08-12 8:18 ` Nicholas Piggin
2020-08-12 10:35 ` peterz
2020-08-18 7:22 ` Nicholas Piggin
2020-08-18 15:41 ` peterz
2020-08-18 23:54 ` Nicholas Piggin
2020-08-19 10:39 ` Alexey Kardashevskiy
2020-08-19 15:32 ` peterz
2020-08-19 15:39 ` peterz [this message]
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