uid_sys_stats: change to use rt_mutex

We see this happens multiple times in heavy workload in systrace
and AMS stuck in uid_lock.

Running process:        Process 953
Running thread: android.ui
State:  Uninterruptible Sleep
Start:
1,025.628 ms
Duration:
27,955.949 ms
On CPU:
Running instead:        system_server
Args:
{kernel callsite when blocked:: "uid_procstat_write+0xb8/0x144"}

Changing to rt_mutex can mitigate the priority inversion

Bug: 34991231
Bug: 34193533
Test: on marlin
Change-Id: I28eb3971331cea60b1075740c792ab87d103262c
Signed-off-by: Wei Wang <wvw@google.com>

1 files changed, 16 insertions, 15 deletions

diff --git a/drivers/misc/uid_sys_stats.c b/drivers/misc/uid_sys_stats.c
index 4988e323cf02..204b23484266 100644
--- a/drivers/misc/uid_sys_stats.c
+++ b/drivers/misc/uid_sys_stats.c
@@ -21,6 +21,7 @@
 #include <linux/list.h>
 #include <linux/proc_fs.h>
 #include <linux/profile.h>
+#include <linux/rtmutex.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
@@ -29,7 +30,7 @@
 #define UID_HASH_BITS	10
 DECLARE_HASHTABLE(hash_table, UID_HASH_BITS);
 
-static DEFINE_MUTEX(uid_lock);
+static DEFINE_RT_MUTEX(uid_lock);
 static struct proc_dir_entry *cpu_parent;
 static struct proc_dir_entry *io_parent;
 static struct proc_dir_entry *proc_parent;
@@ -98,7 +99,7 @@ static int uid_cputime_show(struct seq_file *m, void *v)
 	cputime_t stime;
 	unsigned long bkt;
 
-	mutex_lock(&uid_lock);
+	rt_mutex_lock(&uid_lock);
 
 	hash_for_each(hash_table, bkt, uid_entry, hash) {
 		uid_entry->active_stime = 0;
@@ -111,7 +112,7 @@ static int uid_cputime_show(struct seq_file *m, void *v)
 			current_user_ns(), task_uid(task)));
 		if (!uid_entry) {
 			read_unlock(&tasklist_lock);
-			mutex_unlock(&uid_lock);
+			rt_mutex_unlock(&uid_lock);
 			pr_err("%s: failed to find the uid_entry for uid %d\n",
 				__func__, from_kuid_munged(current_user_ns(),
 				task_uid(task)));
@@ -135,7 +136,7 @@ static int uid_cputime_show(struct seq_file *m, void *v)
 				cputime_to_jiffies(total_stime)) * USEC_PER_MSEC);
 	}
 
-	mutex_unlock(&uid_lock);
+	rt_mutex_unlock(&uid_lock);
 	return 0;
 }
 
@@ -182,7 +183,7 @@ static ssize_t uid_remove_write(struct file *file,
 		kstrtol(end_uid, 10, &uid_end) != 0) {
 		return -EINVAL;
 	}
-	mutex_lock(&uid_lock);
+	rt_mutex_lock(&uid_lock);
 
 	for (; uid_start <= uid_end; uid_start++) {
 		hash_for_each_possible_safe(hash_table, uid_entry, tmp,
@@ -194,7 +195,7 @@ static ssize_t uid_remove_write(struct file *file,
 		}
 	}
 
-	mutex_unlock(&uid_lock);
+	rt_mutex_unlock(&uid_lock);
 	return count;
 }
 
@@ -243,7 +244,7 @@ static void update_io_stats_locked(void)
 	struct io_stats *io_bucket, *io_curr, *io_last;
 	unsigned long bkt;
 
-	BUG_ON(!mutex_is_locked(&uid_lock));
+	BUG_ON(!rt_mutex_is_locked(&uid_lock));
 
 	hash_for_each(hash_table, bkt, uid_entry, hash)
 		memset(&uid_entry->io[UID_STATE_TOTAL_CURR], 0,
@@ -285,7 +286,7 @@ static int uid_io_show(struct seq_file *m, void *v)
 	struct uid_entry *uid_entry;
 	unsigned long bkt;
 
-	mutex_lock(&uid_lock);
+	rt_mutex_lock(&uid_lock);
 
 	update_io_stats_locked();
 
@@ -304,7 +305,7 @@ static int uid_io_show(struct seq_file *m, void *v)
 			uid_entry->io[UID_STATE_BACKGROUND].fsync);
 	}
 
-	mutex_unlock(&uid_lock);
+	rt_mutex_unlock(&uid_lock);
 
 	return 0;
 }
@@ -349,16 +350,16 @@ static ssize_t uid_procstat_write(struct file *file,
 	if (state != UID_STATE_BACKGROUND && state != UID_STATE_FOREGROUND)
 		return -EINVAL;
 
-	mutex_lock(&uid_lock);
+	rt_mutex_lock(&uid_lock);
 
 	uid_entry = find_or_register_uid(uid);
 	if (!uid_entry) {
-		mutex_unlock(&uid_lock);
+		rt_mutex_unlock(&uid_lock);
 		return -EINVAL;
 	}
 
 	if (uid_entry->state == state) {
-		mutex_unlock(&uid_lock);
+		rt_mutex_unlock(&uid_lock);
 		return count;
 	}
 
@@ -366,7 +367,7 @@ static ssize_t uid_procstat_write(struct file *file,
 
 	uid_entry->state = state;
 
-	mutex_unlock(&uid_lock);
+	rt_mutex_unlock(&uid_lock);
 
 	return count;
 }
@@ -388,7 +389,7 @@ static int process_notifier(struct notifier_block *self,
 	if (!task)
 		return NOTIFY_OK;
 
-	mutex_lock(&uid_lock);
+	rt_mutex_lock(&uid_lock);
 	uid = from_kuid_munged(current_user_ns(), task_uid(task));
 	uid_entry = find_or_register_uid(uid);
 	if (!uid_entry) {
@@ -404,7 +405,7 @@ static int process_notifier(struct notifier_block *self,
 	clean_uid_io_last_stats(uid_entry, task);
 
 exit:
-	mutex_unlock(&uid_lock);
+	rt_mutex_unlock(&uid_lock);
 	return NOTIFY_OK;
 }