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-rw-r--r--Documentation/filesystems/proc.txt18
-rw-r--r--fs/proc/base.c67
2 files changed, 85 insertions, 0 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 843b045b4069..7f5607a089b4 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -43,6 +43,7 @@ Table of Contents
3.7 /proc/<pid>/task/<tid>/children - Information about task children
3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
3.9 /proc/<pid>/map_files - Information about memory mapped files
+ 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
4 Configuring procfs
4.1 Mount options
@@ -1862,6 +1863,23 @@ time one can open(2) mappings from the listings of two processes and
comparing their inode numbers to figure out which anonymous memory areas
are actually shared.
+3.10 /proc/<pid>/timerslack_ns - Task timerslack value
+---------------------------------------------------------
+This file provides the value of the task's timerslack value in nanoseconds.
+This value specifies a amount of time that normal timers may be deferred
+in order to coalesce timers and avoid unnecessary wakeups.
+
+This allows a task's interactivity vs power consumption trade off to be
+adjusted.
+
+Writing 0 to the file will set the tasks timerslack to the default value.
+
+Valid values are from 0 - ULLONG_MAX
+
+An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
+permissions on the task specified to change its timerslack_ns value.
+
+
------------------------------------------------------------------------------
Configuring procfs
------------------------------------------------------------------------------
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 4f764c2ac1a5..35f583ad7dbe 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2257,6 +2257,72 @@ static const struct file_operations proc_timers_operations = {
.release = seq_release_private,
};
+static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *offset)
+{
+ struct inode *inode = file_inode(file);
+ struct task_struct *p;
+ u64 slack_ns;
+ int err;
+
+ err = kstrtoull_from_user(buf, count, 10, &slack_ns);
+ if (err < 0)
+ return err;
+
+ p = get_proc_task(inode);
+ if (!p)
+ return -ESRCH;
+
+ if (ptrace_may_access(p, PTRACE_MODE_ATTACH_FSCREDS)) {
+ task_lock(p);
+ if (slack_ns == 0)
+ p->timer_slack_ns = p->default_timer_slack_ns;
+ else
+ p->timer_slack_ns = slack_ns;
+ task_unlock(p);
+ } else
+ count = -EPERM;
+
+ put_task_struct(p);
+
+ return count;
+}
+
+static int timerslack_ns_show(struct seq_file *m, void *v)
+{
+ struct inode *inode = m->private;
+ struct task_struct *p;
+ int err = 0;
+
+ p = get_proc_task(inode);
+ if (!p)
+ return -ESRCH;
+
+ if (ptrace_may_access(p, PTRACE_MODE_ATTACH_FSCREDS)) {
+ task_lock(p);
+ seq_printf(m, "%llu\n", p->timer_slack_ns);
+ task_unlock(p);
+ } else
+ err = -EPERM;
+
+ put_task_struct(p);
+
+ return err;
+}
+
+static int timerslack_ns_open(struct inode *inode, struct file *filp)
+{
+ return single_open(filp, timerslack_ns_show, inode);
+}
+
+static const struct file_operations proc_pid_set_timerslack_ns_operations = {
+ .open = timerslack_ns_open,
+ .read = seq_read,
+ .write = timerslack_ns_write,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
static int proc_pident_instantiate(struct inode *dir,
struct dentry *dentry, struct task_struct *task, const void *ptr)
{
@@ -2831,6 +2897,7 @@ static const struct pid_entry tgid_base_stuff[] = {
#ifdef CONFIG_CHECKPOINT_RESTORE
REG("timers", S_IRUGO, proc_timers_operations),
#endif
+ REG("timerslack_ns", S_IRUGO|S_IWUGO, proc_pid_set_timerslack_ns_operations),
};
static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)