From: Peter Zijlstra <peterz@infradead.org>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Sven Schnelle <svens@linux.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [GIT pull] locking/urgent for v5.10-rc6
Date: Wed, 2 Dec 2020 13:27:34 +0100 [thread overview]
Message-ID: <20201202122734.GH3021@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201202105649.GB6202@osiris>
On Wed, Dec 02, 2020 at 11:56:49AM +0100, Heiko Carstens wrote:
> From 7bd86fb3eb039a4163281472ca79b9158e726526 Mon Sep 17 00:00:00 2001
> From: Heiko Carstens <hca@linux.ibm.com>
> Date: Wed, 2 Dec 2020 11:46:01 +0100
> Subject: [PATCH] s390: fix irq state tracing
>
> With commit 58c644ba512c ("sched/idle: Fix arch_cpu_idle() vs
> tracing") common code calls arch_cpu_idle() with a lockdep state that
> tells irqs are on.
>
> This doesn't work very well for s390: psw_idle() will enable interrupts
> to wait for an interrupt. As soon as an interrupt occurs the interrupt
> handler will verify if the old context was psw_idle(). If that is the
> case the interrupt enablement bits in the old program status word will
> be cleared.
>
> A subsequent test in both the external as well as the io interrupt
> handler checks if in the old context interrupts were enabled. Due to
> the above patching of the old program status word it is assumed the
> old context had interrupts disabled, and therefore a call to
> TRACE_IRQS_OFF (aka trace_hardirqs_off_caller) is skipped. Which in
> turn makes lockdep incorrectly "think" that interrupts are enabled
> within the interrupt handler.
>
> Fix this by unconditionally calling TRACE_IRQS_OFF when entering
> interrupt handlers. Also call unconditionally TRACE_IRQS_ON when
> leaving interrupts handlers.
>
> This leaves the special psw_idle() case, which now returns with
> interrupts disabled, but has an "irqs on" lockdep state. So callers of
> psw_idle() must adjust the state on their own, if required. This is
> currently only __udelay_disabled().
>
> Fixes: 58c644ba512c ("sched/idle: Fix arch_cpu_idle() vs tracing")
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Thanks for sorting this Heiko!
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
next prev parent reply other threads:[~2020-12-02 12:28 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-29 13:37 [GIT pull] irq/urgent for v5.10-rc6 Thomas Gleixner
2020-11-29 13:38 ` [GIT pull] locking/urgent " Thomas Gleixner
2020-11-29 19:31 ` Linus Torvalds
2020-11-30 0:29 ` Paul E. McKenney
2020-11-30 7:56 ` Peter Zijlstra
2020-11-30 8:23 ` Sven Schnelle
2020-11-30 12:31 ` Sven Schnelle
2020-11-30 12:52 ` Peter Zijlstra
2020-11-30 13:03 ` Peter Zijlstra
2020-11-30 18:04 ` Linus Torvalds
2020-11-30 19:31 ` Christian Borntraeger
2020-12-01 8:07 ` Peter Zijlstra
2020-12-01 11:07 ` Peter Zijlstra
2020-12-01 14:46 ` Paul E. McKenney
2020-12-01 14:55 ` Peter Zijlstra
2020-12-01 16:53 ` Paul E. McKenney
2020-12-01 18:15 ` Peter Zijlstra
2020-12-01 18:48 ` Peter Zijlstra
2020-12-01 18:57 ` Mark Rutland
2020-12-01 19:14 ` Peter Zijlstra
2020-12-01 19:18 ` Heiko Carstens
2020-12-02 9:21 ` Peter Zijlstra
2020-12-02 10:56 ` Heiko Carstens
2020-12-02 11:16 ` Mark Rutland
2020-12-02 13:46 ` Heiko Carstens
2020-12-02 12:27 ` Peter Zijlstra [this message]
2020-12-01 7:48 ` Sven Schnelle
2020-12-02 7:54 ` Heiko Carstens
2020-12-02 9:38 ` Peter Zijlstra
2020-12-02 10:52 ` Heiko Carstens
2020-11-30 8:36 ` Peter Zijlstra
2020-11-30 17:55 ` Linus Torvalds
2020-12-01 7:39 ` Peter Zijlstra
2020-12-01 7:56 ` Peter Zijlstra
2020-12-01 19:45 ` Linus Torvalds
2020-12-02 7:53 ` Peter Zijlstra
2020-11-29 20:06 ` pr-tracker-bot
2020-11-29 20:06 ` [GIT pull] irq/urgent " pr-tracker-bot
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