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@xxxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> ---
> 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 ]
