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Message-ID: <29eaed4d-c4e5-cf9b-113b-da146b719820@huawei.com>
Date: Tue, 9 Jan 2024 19:28:29 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: Chen Zhongjin <chenzhongjin@...wei.com>, <linux-kernel@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>
CC: <naveen.n.rao@...ux.ibm.com>, <anil.s.keshavamurthy@...el.com>,
<davem@...emloft.net>, <paulmck@...nel.org>, <mhiramat@...nel.org>,
<akpm@...ux-foundation.org>, <tglx@...utronix.de>, <peterz@...radead.org>,
<pmladek@...e.com>, <dianders@...omium.org>, <npiggin@...il.com>,
<mpe@...erman.id.au>, <jkl820.git@...il.com>,
<juerg.haefliger@...onical.com>, <rick.p.edgecombe@...el.com>,
<eric.devolder@...cle.com>, <mic@...ikod.net>
Subject: Re: [RFC PATCH] kprobes: Use synchronize_rcu_tasks_rude in
kprobe_optimizer
Hello,
PING.
I had a similar problem. Is this solution feasible?
Thanks,
Yang
On 2024/1/2 11:40, Chen Zhongjin wrote:
> There is a deadlock scenario in kprobe_optimizer():
>
> pid A pid B pid C
> kprobe_optimizer() do_exit() perf_kprobe_init()
> mutex_lock(&kprobe_mutex) exit_tasks_rcu_start() mutex_lock(&kprobe_mutex)
> synchronize_rcu_tasks() zap_pid_ns_processes() // waiting kprobe_mutex
> // waiting tasks_rcu_exit_srcu kernel_wait4()
> // waiting pid C exit
>
> To avoid this deadlock loop, use synchronize_rcu_tasks_rude() in kprobe_optimizer()
> rather than synchronize_rcu_tasks(). synchronize_rcu_tasks_rude() can also promise
> that all preempted tasks have scheduled, but it will not wait tasks_rcu_exit_srcu.
>
> Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
> ---
> arch/Kconfig | 2 +-
> kernel/kprobes.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index f4b210ab0612..dc6a18854017 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -104,7 +104,7 @@ config STATIC_CALL_SELFTEST
> config OPTPROBES
> def_bool y
> depends on KPROBES && HAVE_OPTPROBES
> - select TASKS_RCU if PREEMPTION
> + select TASKS_RUDE_RCU
>
> config KPROBES_ON_FTRACE
> def_bool y
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index d5a0ee40bf66..09056ae50c58 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -623,7 +623,7 @@ static void kprobe_optimizer(struct work_struct *work)
> * Note that on non-preemptive kernel, this is transparently converted
> * to synchronoze_sched() to wait for all interrupts to have completed.
> */
> - synchronize_rcu_tasks();
> + synchronize_rcu_tasks_rude();
>
> /* Step 3: Optimize kprobes after quiesence period */
> do_optimize_kprobes();
>
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