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Commit 3291cd6f authored by Wei Wang's avatar Wei Wang Committed by Amit Pundir
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ANDROID: 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: default avatarWei Wang <wvw@google.com>
parent bfb2eaf0

drivers/misc/uid_sys_stats.c

+17 −15
Original line number Diff line number Diff line
@@ -21,15 +21,17 @@ 
#include <linux/list.h>

#include <linux/proc_fs.h>

#include <linux/profile.h>

#include <linux/rtmutex.h>

#include <linux/sched/cputime.h>

#include <linux/seq_file.h>

#include <linux/slab.h>

#include <linux/uaccess.h>





#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 +100,7 @@ static int uid_cputime_show(struct seq_file *m, void *v) 
	u64 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 +113,7 @@ 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)));
@@ -132,7 +134,7 @@ static int uid_cputime_show(struct seq_file *m, void *v) 
			ktime_to_ms(total_utime), ktime_to_ms(total_stime));

	}



	mutex_unlock(&uid_lock);

	rt_mutex_unlock(&uid_lock);

	return 0;

}
@@ -179,7 +181,7 @@ 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,
@@ -191,7 +193,7 @@ static ssize_t uid_remove_write(struct file *file, 
		}

	}



	mutex_unlock(&uid_lock);

	rt_mutex_unlock(&uid_lock);

	return count;

}
@@ -240,7 +242,7 @@ 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,
@@ -282,7 +284,7 @@ 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();
@@ -301,7 +303,7 @@ 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;

}
@@ -346,16 +348,16 @@ 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;

	}
@@ -363,7 +365,7 @@ static ssize_t uid_procstat_write(struct file *file, 


	uid_entry->state = state;



	mutex_unlock(&uid_lock);

	rt_mutex_unlock(&uid_lock);



	return count;

}
@@ -385,7 +387,7 @@ 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) {
@@ -401,7 +403,7 @@ 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;

}