From: Marco Elver <elver@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Ahmed S. Darwish" <a.darwish@linutronix.de>,
mingo@kernel.org, will@kernel.org, tglx@linutronix.de,
x86@kernel.org, linux-kernel@vger.kernel.org,
rostedt@goodmis.org, bigeasy@linutronix.de, davem@davemloft.net,
sparclinux@vger.kernel.org, mpe@ellerman.id.au,
linuxppc-dev@lists.ozlabs.org, heiko.carstens@de.ibm.com,
linux-s390@vger.kernel.org, linux@armlinux.org.uk
Subject: Re: [PATCH v4 7/8] lockdep: Change hardirq{s_enabled,_context} to per-cpu variables
Date: Tue, 23 Jun 2020 19:59:57 +0200 [thread overview]
Message-ID: <20200623175957.GA106514@elver.google.com> (raw)
In-Reply-To: <20200623163730.GA4800@hirez.programming.kicks-ass.net>
On Tue, Jun 23, 2020 at 06:37PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 23, 2020 at 06:13:21PM +0200, Ahmed S. Darwish wrote:
> > Well, freshly merged code is using it. For example, KCSAN:
> >
> > => f1bc96210c6a ("kcsan: Make KCSAN compatible with lockdep")
> > => kernel/kcsan/report.c:
> >
> > void kcsan_report(...)
> > {
> > ...
> > /*
> > * With TRACE_IRQFLAGS, lockdep's IRQ trace state becomes corrupted if
> > * we do not turn off lockdep here; this could happen due to recursion
> > * into lockdep via KCSAN if we detect a race in utilities used by
> > * lockdep.
> > */
> > lockdep_off();
> > ...
> > }
>
> Marco, do you remember what exactly happened there? Because I'm about to
> wreck that. That is, I'm going to make TRACE_IRQFLAGS ignore
> lockdep_off().
Yeah, I was trying to squash any kind of recursion:
lockdep -> other libs ->
-> KCSAN
-> print report
-> dump stack, printk and friends
-> lockdep -> other libs
-> KCSAN ...
Some history:
* Initial patch to fix:
https://lore.kernel.org/lkml/20200115162512.70807-1-elver@google.com/
* KCSAN+lockdep+ftrace:
https://lore.kernel.org/lkml/20200214211035.209972-1-elver@google.com/
lockdep now has KCSAN_SANITIZE := n, but we still need to ensure that
there are no paths out of lockdep, or the IRQ flags tracing code, that
might lead through other libs, through KCSAN, libs used to generate a
report, and back to lockdep.
I never quite figured out the exact trace that led to corruption, but
avoiding any kind of potential for recursion was the only thing that
would avoid the check_flags() warnings.
Thanks,
-- Marco
next prev parent reply other threads:[~2020-06-23 18:00 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 8:36 [PATCH v4 0/8] lockdep: Change IRQ state tracking to use per-cpu variables Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 1/8] lockdep: Prepare for NMI IRQ state tracking Peter Zijlstra
2020-07-11 10:09 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 2/8] x86/entry: Fix NMI vs " Peter Zijlstra
2020-07-11 10:09 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 3/8] sparc64: Fix asm/percpu.h build error Peter Zijlstra
2020-06-23 21:35 ` David Miller
2020-07-11 10:09 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 4/8] powerpc64: Break asm/percpu.h vs spinlock_types.h dependency Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 5/8] s390: Break cyclic percpu include Peter Zijlstra
2020-07-11 10:09 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 6/8] arm: " Peter Zijlstra
2020-06-23 9:02 ` Will Deacon
2020-06-24 17:53 ` Peter Zijlstra
2020-06-25 7:31 ` Will Deacon
2020-07-11 10:09 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 7/8] lockdep: Change hardirq{s_enabled,_context} to per-cpu variables Peter Zijlstra
2020-06-23 15:00 ` Ahmed S. Darwish
2020-06-23 15:24 ` Peter Zijlstra
2020-06-23 16:13 ` Ahmed S. Darwish
2020-06-23 16:37 ` Peter Zijlstra
2020-06-23 17:59 ` Marco Elver [this message]
2020-06-23 18:12 ` Peter Zijlstra
2020-06-23 18:39 ` Marco Elver
2020-06-23 19:13 ` Marco Elver
2020-06-23 19:41 ` Peter Zijlstra
2020-06-23 20:08 ` Peter Zijlstra
2020-06-23 20:24 ` Peter Zijlstra
2020-06-23 20:33 ` Peter Zijlstra
2020-06-24 9:00 ` Peter Zijlstra
2020-06-24 10:17 ` Marco Elver
2020-06-24 12:31 ` Peter Zijlstra
2020-06-24 11:32 ` Marco Elver
2020-06-24 15:18 ` Peter Zijlstra
2020-07-11 10:09 ` [tip: locking/core] kcsan: Make KCSAN compatible with new IRQ state tracking tip-bot2 for Marco Elver
2020-06-30 5:59 ` [PATCH v4 7/8] lockdep: Change hardirq{s_enabled,_context} to per-cpu variables Ahmed S. Darwish
2020-06-30 9:40 ` Peter Zijlstra
2020-07-11 10:09 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2020-06-23 8:36 ` [PATCH v4 8/8] lockdep: Remove lockdep_hardirq{s_enabled,_context}() argument Peter Zijlstra
2020-07-11 10:09 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
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