[PATCH] hungtask: add filter kthread/check comm

From: chenguanyou
Date: Fri May 21 2021 - 09:26:46 EST

Some kernel threads are always in D state, when we enable hung_task,
it will misjudge, we should skip these to narrow the scope.

exp mtk mobilephone:
root 435 435 2 0 0 mtk_lpm_monitor_thread 0 D LPM-0
root 436 436 2 0 0 mtk_lpm_monitor_thread 0 D LPM-1
root 437 437 2 0 0 mtk_lpm_monitor_thread 0 D LPM-2
root 438 438 2 0 0 mtk_lpm_monitor_thread 0 D LPM-3
root 439 439 2 0 0 mtk_lpm_monitor_thread 0 D LPM-4
root 440 440 2 0 0 mtk_lpm_monitor_thread 0 D LPM-5
root 441 441 2 0 0 mtk_lpm_monitor_thread 0 D LPM-6
root 442 442 2 0 0 mtk_lpm_monitor_thread 0 D LPM-7

Signed-off-by: chenguanyou <chenguanyou@xxxxxxxxxx>
---
Documentation/admin-guide/sysctl/kernel.rst | 16 ++++++++++++
include/linux/sched/sysctl.h | 4 +++
kernel/hung_task.c | 17 +++++++++++++
kernel/sysctl.c | 16 ++++++++++++
lib/Kconfig.debug | 27 +++++++++++++++++++++
5 files changed, 80 insertions(+)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 1d56a6b73a4e..081ca22db4d5 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -405,6 +405,22 @@ This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.

-1: report an infinite number of warnings.

+hung_task_filter_kthread
+========================
+
+We should skip kthread when a hung task is detected.
+This file shows up if ``CONFIG_DEFAULT_HUNG_TASK_FILTER_KTHREAD`` is enabled.
+
+= =========================================================
+0 Not skip detect kthread.
+1 Skip detect kthread.
+= =========================================================
+
+hung_task_check_comm
+====================
+
+We should skip non ``hung_task_check_comm`` when a hung task is detected.
+This file shows up if ``CONFIG_DEFAULT_HUNG_TASK_CHECK_COMM`` is enabled.

hyperv_record_panic_msg
=======================
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 3c31ba88aca5..e8a9a28215bf 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -14,11 +14,15 @@ extern unsigned int sysctl_hung_task_all_cpu_backtrace;
#define sysctl_hung_task_all_cpu_backtrace 0
#endif /* CONFIG_SMP */

+#define TASK_COMM_LEN 16
+
extern int sysctl_hung_task_check_count;
extern unsigned int sysctl_hung_task_panic;
extern unsigned long sysctl_hung_task_timeout_secs;
extern unsigned long sysctl_hung_task_check_interval_secs;
extern int sysctl_hung_task_warnings;
+extern unsigned int sysctl_hung_task_filter_kthread;
+extern char sysctl_hung_task_check_comm[TASK_COMM_LEN];
int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos);
#else
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 396ebaebea3f..baee8466b902 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -23,6 +23,7 @@
#include <linux/sched/sysctl.h>

#include <trace/events/sched.h>
+#include <linux/string.h>

/*
* The number of tasks checked:
@@ -48,6 +49,16 @@ unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_
*/
unsigned long __read_mostly sysctl_hung_task_check_interval_secs;

+/*
+ * Non-zero means no checking kthread
+ */
+unsigned int __read_mostly sysctl_hung_task_filter_kthread = CONFIG_DEFAULT_HUNG_TASK_FILTER_KTHREAD;
+
+/*
+ * Only one
+ */
+char __read_mostly sysctl_hung_task_check_comm[TASK_COMM_LEN] = CONFIG_DEFAULT_HUNG_TASK_CHECK_COMM;
+
int __read_mostly sysctl_hung_task_warnings = 10;

static int __read_mostly did_panic;
@@ -88,6 +99,12 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
{
unsigned long switch_count = t->nvcsw + t->nivcsw;

+ if (unlikely(strlen(sysctl_hung_task_check_comm) && !strstr(t->comm, sysctl_hung_task_check_comm)))
+ return;
+
+ if (unlikely(sysctl_hung_task_filter_kthread && t->flags & PF_KTHREAD))
+ return;
+
/*
* Ensure the task is not frozen.
* Also, skip vfork and any other user process that freezer should skip.
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 62fbd09b5dc1..1daede87c88d 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2519,6 +2519,22 @@ static struct ctl_table kern_table[] = {
.proc_handler = proc_dointvec_minmax,
.extra1 = &neg_one,
},
+ {
+ .procname = "hung_task_filter_kthread",
+ .data = &sysctl_hung_task_filter_kthread,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE,
+ },
+ {
+ .procname = "hung_task_check_comm",
+ .data = &sysctl_hung_task_check_comm,
+ .maxlen = TASK_COMM_LEN,
+ .mode = 0644,
+ .proc_handler = proc_dostring,
+ },
#endif
#ifdef CONFIG_RT_MUTEXES
{
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2c7f46b366f1..63570b1fec35 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1101,6 +1101,33 @@ config DEFAULT_HUNG_TASK_TIMEOUT
A timeout of 0 disables the check. The default is two minutes.
Keeping the default should be fine in most cases.

+config DEFAULT_HUNG_TASK_FILTER_KTHREAD
+ int "Default filter kthread for hung task"
+ depends on DETECT_HUNG_TASK
+ range 0 1
+ default 0
+ help
+ This option controls filter kthread uses to determine when
+ a kernel task has become "state=TASK_UNINTERRUPTIBLE" and should be skipped.
+
+ It can be adjusted at runtime via the kernel.hung_task_filter_kthread
+ sysctl or by writing a value to
+ /proc/sys/kernel/hung_task_filter_kthread.
+
+ A filter of 1 disables the check.
+
+config DEFAULT_HUNG_TASK_CHECK_COMM
+ string "Default check only one comm"
+ depends on DETECT_HUNG_TASK
+ default ""
+ help
+ This option controls only detect "task.comm = kernel.hung_task_check_comm" when
+ it become "state=TASK_UNINTERRUPTIBLE", skip other threads.
+
+ It can be adjusted at runtime via the kernel.hung_task_check_comm
+ sysctl or by writing a value to
+ /proc/sys/kernel/hung_task_check_comm.
+
config BOOTPARAM_HUNG_TASK_PANIC
bool "Panic (Reboot) On Hung Tasks"
depends on DETECT_HUNG_TASK
--
2.17.1