The patch titled
Subject: kprobes: use synchronize_rcu_tasks_rude in kprobe_optimizer
has been added to the -mm mm-nonmm-unstable branch. Its filename is
kprobes-use-synchronize_rcu_tasks_rude-in-kprobe_optimizer.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kprobes-use-synchronize_rcu_tasks_rude-in-kprobe_optimizer.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
Subject: kprobes: use synchronize_rcu_tasks_rude in kprobe_optimizer
Date: Wed, 17 Jan 2024 06:16:36 +0000
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.
Link: https://lkml.kernel.org/r/20240117061636.288412-1-chenzhongjin@xxxxxxxxxx
Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
Cc: Eric DeVolder <eric.devolder@xxxxxxxxxx>
Cc: Jakob Koschel <jkl820.git@xxxxxxxxx>
Cc: Juerg Haefliger <juerg.haefliger@xxxxxxxxxxxxx>
Cc: "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> (powerpc)
Cc: Mickaël Salaün <mic@xxxxxxxxxxx>
Cc: "Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Cc: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Yang Jihong <yangjihong1@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/Kconfig | 2 +-
kernel/kprobes.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
--- a/arch/Kconfig~kprobes-use-synchronize_rcu_tasks_rude-in-kprobe_optimizer
+++ a/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
--- a/kernel/kprobes.c~kprobes-use-synchronize_rcu_tasks_rude-in-kprobe_optimizer
+++ a/kernel/kprobes.c
@@ -623,7 +623,7 @@ static void kprobe_optimizer(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();
_
Patches currently in -mm which might be from chenzhongjin@xxxxxxxxxx are
kprobes-use-synchronize_rcu_tasks_rude-in-kprobe_optimizer.patch
