linux-kernel - Re: [PATCH] clocksource/arm_arch_timer: mark arch_timer_read

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Message-ID: <9a68f57b-98f4-c2ba-25cb-20ad745f6af5@arm.com>
Date:   Tue, 11 Jun 2019 16:25:26 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Wei Li <liwei391@...wei.com>, mark.rutland@....com,
        daniel.lezcano@...aro.org, tglx@...utronix.de
Cc:     huawei.libin@...wei.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clocksource/arm_arch_timer: mark
 arch_timer_read_counter() as notrace to avoid deadloop

Hi Wei,

On 11/06/2019 16:21, Wei Li wrote:
> According to arch_counter_register(), mark arch_counter_get_*() what
> arch_timer_read_counter() can be as notrace to avoid deadloop when using
> function_graph tracer.
> 
>  0xffff80028af23250 0xffff000010195e00 sched_clock+64
>  0xffff80028af23290 0xffff0000101e83ec trace_clock_local+12
>  0xffff80028af232a0 0xffff00001020e52c function_graph_enter+116
>  0xffff80028af23300 0xffff00001009af9c prepare_ftrace_return+44
>  0xffff80028af23320 0xffff00001009b0a8 ftrace_graph_caller+28
>  0xffff80028af23330 0xffff000010b01918 arch_counter_get_cntvct+16
>  0xffff80028af23340 0xffff000010195e00 sched_clock+64
>  0xffff80028af23380 0xffff0000101e83ec trace_clock_local+12
>  0xffff80028af23390 0xffff00001020e52c function_graph_enter+116
>  0xffff80028af233f0 0xffff00001009af9c prepare_ftrace_return+44
>  0xffff80028af23410 0xffff00001009b0a8 ftrace_graph_caller+28
>  0xffff80028af23420 0xffff000010b01918 arch_counter_get_cntvct+16
>  ...
> 
> Fixes: 0ea415390cd3 ("clocksource/arm_arch_timer: Use arch_timer_read_counter to access stable counters")
> Signed-off-by: Wei Li <liwei391@...wei.com>

There is already a patch[1] queued for that. Hopefully Daniel
and Thomas will get this into mainline shortly.

Thanks,

	M.

[1] https://lore.kernel.org/lkml/20190524093600.11ca3cb2@gandalf.local.home/T/
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