[PATCH] kernel/hung_task: Add a whitelist and blacklist mechanism.

[zhouchuangao]

The main purpose of this patch is to add a whitelist and blacklist
mechanism to the hung task thread.

1. Add a /sys/module/hung_task/parameters/hung_seconds interface,
so you can write a specific time to 'hung_seconds' to hang a shell
process for a while. This interface is convenient for us to debug
the function of hung task thread.
eg:
echo 100 > /sys/module/hung_task/parameters/hung_seconds
This will put the current shell process into D state for 100s.

2. Add whitelist and blacklist. If a D state process is on the
whitelist, it will skip checking for that process. In contrast, if
the process is on a blacklist, panic is triggered.
Different use scenarios can make different whitelist and blacklist.

eg:
In Android system, we usually and some processes to the whitelist.
static task_t task_whitelist[] = {
	{"mdrt_thread", HUNG_TASK_WHITELIST},
	{"chre_kthread", HUNG_TASK_WHITELIST},
	{"scp_power_reset", HUNG_TASK_WHITELIST},
	{"ccci_fsm1", HUNG_TASK_WHITELIST},
	{"qos_ipi_recv", HUNG_TASK_WHITELIST},
	{NULL, 0},
};

3. Add a new member hung_state to task_struct to identify the type
of the D state process being detected.
A value of 0x1(HUNG_TASK_WHITELIST) indicates that the process is
on the whitelist.
A value of 0x2(HUNG_TASK_BLACKLIST) indicates that the process is
on the blacklist.
The remaining bits are reserved, and there may be other scenarios
entering the D state that need to be added to hung_state.

Signed-off-by: zhouchuangao <zhouchuangao@xxxxxxxx>
---
 include/linux/sched.h |  1 +
 kernel/hung_task.c    | 88 +++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8d5264b..8ffbdf6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -973,6 +973,7 @@ struct task_struct {
 	unsigned long			last_switch_count;
 	unsigned long			last_switch_time;
 	unsigned long			killed_time;
+	unsigned long			hung_state;
 #endif
 	/* Filesystem information: */
 	struct fs_struct		*fs;
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index bb2e3e1..952a44c 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -72,6 +72,57 @@ unsigned int __read_mostly sysctl_hung_task_all_cpu_backtrace;
 unsigned int __read_mostly sysctl_hung_task_panic =
 				CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE;
 
+#define HUNG_TASK_WHITELIST		0x1
+#define HUNG_TASK_BLACKLIST		0x2
+
+typedef struct {
+	char *task_comm;
+	unsigned long flag;
+} task_t;
+
+static task_t task_whitelist[] = {
+	{NULL, 0},
+};
+
+static task_t task_blacklist[] = {
+	{"init", HUNG_TASK_BLACKLIST},
+	{NULL, 0},
+};
+
+static bool task_in_blacklist(struct task_struct *tsk)
+{
+	task_t *info = NULL;
+
+	if (tsk->hung_state & HUNG_TASK_BLACKLIST)
+		return true;
+
+	for (info = task_blacklist; info->task_comm; info++) {
+		if (!strcmp(tsk->comm, info->task_comm)) {
+			tsk->hung_state |= HUNG_TASK_BLACKLIST;
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static bool task_in_whitelist(struct task_struct *tsk)
+{
+	task_t *info = NULL;
+
+	if (tsk->hung_state & HUNG_TASK_WHITELIST)
+		return true;
+
+	for (info = task_whitelist; info->task_comm; info++) {
+		if (!strcmp(tsk->comm, info->task_comm)) {
+			tsk->hung_state |= HUNG_TASK_WHITELIST;
+			return true;
+		}
+	}
+
+	return false;
+}
+
 static int
 hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
 {
@@ -111,6 +162,12 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 	if (time_is_after_jiffies(t->last_switch_time + timeout * HZ))
 		return;
 
+	/* Check if process 't' is in the whitelist. */
+	if (task_in_whitelist(t)) {
+		pr_info("skip hung task: %s\n", t->comm);
+		return;
+	}
+
 	trace_sched_process_hang(t);
 
 	if (sysctl_hung_task_panic) {
@@ -118,7 +175,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 		hung_task_show_lock = true;
 		hung_task_call_panic = true;
 	}
-
 	/*
 	 * Ok, the task did not get scheduled for more than 2 minutes,
 	 * complain:
@@ -141,6 +197,12 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 			hung_task_show_all_bt = true;
 	}
 
+	/* Check if process 't' is in the blacklist. */
+	if (task_in_blacklist(t)) {
+		pr_err("critical task blocked: (%d)%s\n", t->pid, t->comm);
+		hung_task_call_panic = true;
+	}
+
 	touch_nmi_watchdog();
 }
 
@@ -253,8 +315,10 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 		trigger_all_cpu_backtrace();
 	}
 
-	if (hung_task_call_panic)
+	if (hung_task_call_panic) {
+		show_state_filter(TASK_UNINTERRUPTIBLE);
 		panic("hung_task: blocked tasks");
+	}
 }
 
 static long hung_timeout_jiffies(unsigned long last_checked,
@@ -322,6 +386,7 @@ static int watchdog(void *dummy)
 	unsigned long hung_last_checked = jiffies;
 
 	set_user_nice(current, 0);
+	pr_info("khungtaskd started...\n");
 
 	for ( ; ; ) {
 		unsigned long timeout = sysctl_hung_task_timeout_secs;
@@ -357,3 +422,22 @@ static int __init hung_task_init(void)
 	return 0;
 }
 subsys_initcall(hung_task_init);
+
+static int hung_task_test(const char *val, const struct kernel_param *kp)
+{
+	unsigned long sec = 0;
+	if (kstrtoul(val, 10, &sec))
+		return -EINVAL;
+
+	pr_info("Hung task Dsleep %ld s, start!\n", sec);
+	msleep(sec * 1000);
+	pr_info("Hung task Dsleep %ld s, end!\n", sec);
+
+	return 0;
+}
+
+static const struct kernel_param_ops hung_task_test_ops = {
+	.set = hung_task_test,
+};
+
+module_param_cb(hung_seconds, &hung_task_test_ops, NULL, 0600);
-- 
2.7.4