linux-kernel - [Race condition] Race condition at cpuidle_enter_s2idle & __cfi_slowpath

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Message-ID: <3bcf5d974b98acccde89e8d5567d3ddcdfb44800.camel@mediatek.com>
Date:   Thu, 11 Aug 2022 15:54:28 +0800
From:   Kuyo Chang <kuyo.chang@...iatek.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        "Vincent Guittot" <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Ben Segall" <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        "Daniel Bristot de Oliveira" <bristot@...hat.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, <rcu@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Daniel Lezcano" <daniel.lezcano@...aro.org>
CC:     <kuyo.chang@...iatek.com>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <wsd_upstream@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <rcu@...r.kernel.org>,
        <llvm@...ts.linux.dev>
Subject: [Race condition] Race condition at cpuidle_enter_s2idle &
 __cfi_slowpath_diag

Hi Sami,

During doing s2idle(Suspend-To-Idle) flow, I found a task will put into
runqueue by __cfi_slowpath_diag.
The code trace about fail case as below:

call_cpuidle_s2idle
->if (current_clr_polling_and_test()) //check resched flag
	return -EBUSY;
->cpuidle_enter_s2idle
->enter_s2idle_proper
->target_state->enter_s2idle(dev, drv, index);

Meanwhile the log shows the __cfi_slowpath_diag function will wake up a
task to CPU, below is the backtrace
__cfi_slowpath_diag
find_check_fn
rcu_irq_enter
rcu_nmi_enter
rcu_cleanup_after_idle
invoke_rcu_core
raise_softirq(RCU_SOFTIRQ)
raise_softirq_irqoff
    if (!in_interrupt() && should_wake_ksoftirqd())
        wakeup_softirqd();
//wake up flow
wake_up_process
try_to_wake_up
ttwu_queue
ttwu_do_activate
ttwu_do_wakeup
check_preempt_curr
resched_curr
set_tsk_need_resched(curr);
 

So It will violate the initial check at call_cpuidle_s2idle(Now it
exists a task at rq  and need reched, so it should not enter
cpuidle_enter_s2idle )
if (current_clr_polling_and_test())
	return -EBUSY;

I look the racing may be related to the following patch

57cd6d1 cfi: Fix __cfi_slowpath_diag RCU usage with cpuidle
https://android.googlesource.com/kernel/common/+/57cd6d1

Do you have any suggestion for this issue?
Thank you.