From: Peter Zijlstra <peterz@infradead.org>
To: Daniel Thompson <daniel.thompson@linaro.org>
Cc: sumit.garg@linaro.org, jason.wessel@windriver.com,
dianders@chromium.org, kgdb-bugreport@lists.sourceforge.net,
linux-kernel@vger.kernel.org, patches@linaro.org,
pmladek@suse.com, sergey.senozhatsky@gmail.com,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
Subject: Re: [RFC PATCH 2/2] locking/spinlock/debug: Add checks for kgdb trap safety
Date: Fri, 22 May 2020 18:35:04 +0200 [thread overview]
Message-ID: <20200522163504.GX317569@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200522145510.2109799-3-daniel.thompson@linaro.org>
On Fri, May 22, 2020 at 03:55:10PM +0100, Daniel Thompson wrote:
> In general it is not safe to call spin_lock() whilst executing in the
> kgdb trap handler. The trap can be entered from all sorts of execution
> context (NMI, IRQ, irqs disabled, etc) and the kgdb/kdb needs to be
> as resillient as possible.
>
> Currently it is difficult to spot mistakes in the kgdb/kdb logic
> (especially so for kdb because it uses more kernel features than
> pure-kgdb). Let's provide a means to bring attention to deadlock
> risks in the debug code.
I really dislike this thing. Also, commit:
f6f48e180404 ("lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions")
should be able to trigger here when the kgdb traps are marked as NMI.
x86 will soon have that.
prev parent reply other threads:[~2020-05-22 16:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-22 14:55 [RFC PATCH 0/2] Introduce KGDB_DEBUG_SPINLOCKS Daniel Thompson
2020-05-22 14:55 ` [RFC PATCH 1/2] debug: Convert dbg_slave_lock to an atomic Daniel Thompson
2020-05-22 16:26 ` Peter Zijlstra
2020-05-22 14:55 ` [RFC PATCH 2/2] locking/spinlock/debug: Add checks for kgdb trap safety Daniel Thompson
2020-05-22 16:35 ` Peter Zijlstra [this message]
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