From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
To: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
Xuefeng Li <lixuefeng@loongson.cn>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 2/2] MIPS: Fix kernel hang under FUNCTION_GRAPH_TRACER and PREEMPT_TRACER
Date: Tue, 25 May 2021 15:38:58 +0200 [thread overview]
Message-ID: <20210525133858.GA11166@alpha.franken.de> (raw)
In-Reply-To: <1621076521-22412-3-git-send-email-yangtiezhu@loongson.cn>
On Sat, May 15, 2021 at 07:02:01PM +0800, Tiezhu Yang wrote:
> When update the latest mainline kernel with the following three configs,
> the kernel hangs during startup:
>
> (1) CONFIG_FUNCTION_GRAPH_TRACER=y
> (2) CONFIG_PREEMPT_TRACER=y
> (3) CONFIG_FTRACE_STARTUP_TEST=y
>
> When update the latest mainline kernel with the above two configs (1)
> and (2), the kernel starts normally, but it still hangs when execute
> the following command:
>
> echo "function_graph" > /sys/kernel/debug/tracing/current_tracer
>
> Without CONFIG_PREEMPT_TRACER=y, the above two kinds of kernel hangs
> disappeared, so it seems that CONFIG_PREEMPT_TRACER has some influences
> with function_graph tracer at the first glance.
>
> I use ejtag to find out the epc address is related with preempt_enable()
> in the file arch/mips/lib/mips-atomic.c, because function tracing can
> trace the preempt_{enable,disable} calls that are traced, replace them
> with preempt_{enable,disable}_notrace to prevent function tracing from
> going into an infinite loop, and then it can fix the kernel hang issue.
>
> By the way, it seems that this commit is a complement and improvement of
> commit f93a1a00f2bd ("MIPS: Fix crash that occurs when function tracing
> is enabled").
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> ---
> arch/mips/lib/mips-atomic.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
applied to mips-fixes.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
prev parent reply other threads:[~2021-05-25 13:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-15 11:01 [PATCH 0/2] Update defconfig and fix kernel hang Tiezhu Yang
2021-05-15 11:02 ` [PATCH 1/2] MIPS: Loongson64: Update loongson3_defconfig Tiezhu Yang
2021-05-27 11:42 ` Thomas Bogendoerfer
2021-05-15 11:02 ` [PATCH 2/2] MIPS: Fix kernel hang under FUNCTION_GRAPH_TRACER and PREEMPT_TRACER Tiezhu Yang
2021-05-25 13:38 ` Thomas Bogendoerfer [this message]
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