1 files changed, 70 insertions, 1 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 4f764c2ac1a5..b1755b23893e 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -434,7 +434,7 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
                         && !lookup_symbol_name(wchan, symname))
                 seq_printf(m, "%s", symname);
         else
-                seq_putc(m, '0');
+                seq_puts(m, "0\n");
 
         return 0;
 }
@@ -2158,6 +2158,7 @@ static const struct file_operations proc_map_files_operations = {
         .llseek         = default_llseek,
 };
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
 struct timers_private {
         struct pid *pid;
         struct task_struct *task;
@@ -2256,6 +2257,73 @@ static const struct file_operations proc_timers_operations = {
         .llseek         = seq_lseek,
         .release        = seq_release_private,
 };
+#endif
+
+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 +2899,7 @@ 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)