linux-kernel - Re: [PATCH] drivers: qcom: rpmh-rsc: Use rcuidle tracepoints for rpmh

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Message-ID: <CAD=FV=XS4iPbxzBNHrmEQYCy5uEzce3Oucu-Jveoycc8hJn10A@mail.gmail.com>
Date:   Wed, 15 Jan 2020 10:18:55 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH] drivers: qcom: rpmh-rsc: Use rcuidle tracepoints for rpmh

Hi,

On Tue, Jan 14, 2020 at 5:37 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> This tracepoint is hit now that we call into the rpmh code from the cpu
> idle path. Let's move this to be an rcuidle tracepoint so that we avoid
> the RCU idle splat below
>
>  =============================
>  WARNING: suspicious RCU usage
>  5.4.10 #68 Tainted: G S
>  -----------------------------
>  drivers/soc/qcom/trace-rpmh.h:72 suspicious rcu_dereference_check() usage!
>
>  other info that might help us debug this:
>
>  RCU used illegally from idle CPU!
>  rcu_scheduler_active = 2, debug_locks = 1
>  RCU used illegally from extended quiescent state!
>  5 locks held by swapper/2/0:
>   #0: ffffff81745d6ee8 (&(&genpd->slock)->rlock){+.+.}, at: genpd_lock_spin+0x1c/0x2c
>   #1: ffffff81745da6e8 (&(&genpd->slock)->rlock/1){....}, at: genpd_lock_nested_spin+0x24/0x34
>   #2: ffffff8174f2ca20 (&(&genpd->slock)->rlock/2){....}, at: genpd_lock_nested_spin+0x24/0x34
>   #3: ffffff8174f2c300 (&(&drv->client.cache_lock)->rlock){....}, at: rpmh_flush+0x48/0x24c
>   #4: ffffff8174f2c150 (&(&tcs->lock)->rlock){+.+.}, at: rpmh_rsc_write_ctrl_data+0x74/0x270
>
>  stack backtrace:
>  CPU: 2 PID: 0 Comm: swapper/2 Tainted: G S                5.4.10 #68
>  Call trace:
>   dump_backtrace+0x0/0x174
>   show_stack+0x20/0x2c
>   dump_stack+0xc8/0x124
>   lockdep_rcu_suspicious+0xe4/0x104
>   __tcs_buffer_write+0x230/0x2d0
>   rpmh_rsc_write_ctrl_data+0x210/0x270
>   rpmh_flush+0x84/0x24c
>   rpmh_domain_power_off+0x78/0x98
>   _genpd_power_off+0x40/0xc0
>   genpd_power_off+0x168/0x208
>   genpd_power_off+0x1e0/0x208
>   genpd_power_off+0x1e0/0x208
>   genpd_runtime_suspend+0x1ac/0x220
>   __rpm_callback+0x70/0xfc
>   rpm_callback+0x34/0x8c
>   rpm_suspend+0x218/0x4a4
>   __pm_runtime_suspend+0x88/0xac
>   psci_enter_domain_idle_state+0x3c/0xb4
>   cpuidle_enter_state+0xb8/0x284
>   cpuidle_enter+0x38/0x4c
>   call_cpuidle+0x3c/0x68
>   do_idle+0x194/0x260
>   cpu_startup_entry+0x24/0x28
>   secondary_start_kernel+0x150/0x15c
>
> Fixes: a65a397f2451 ("cpuidle: psci: Add support for PM domains by using genpd")
> Reported-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>
> I think the commit that this is "Fixes"ing is a stable commit, but I'm
> not positive.
>
>  drivers/soc/qcom/rpmh-rsc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

I'm not an expert on these code path, but it looks sane to me.

Reviewed-by: Douglas Anderson <dianders@...omium.org>