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authorJohn Stultz <john.stultz@linaro.org>2016-03-17 14:20:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-17 15:09:34 -0700
commit5de23d435e88996b1efe0e2cebe242074ce67c9e (patch)
tree05a4398e63bdb5f2151dfff33894c5f5b4061822 /fs
parentda8b44d5a9f8bf26da637b7336508ca534d6b319 (diff)
proc: add /proc/<pid>/timerslack_ns interface
This patch provides a proc/PID/timerslack_ns interface which exposes a task's timerslack value in nanoseconds and allows it to be changed. This allows power/performance management software to set timer slack for other threads according to its policy for the thread (such as when the thread is designated foreground vs. background activity) If the value written is non-zero, slack is set to that value. Otherwise sets it to the default for the thread. This interface checks that the calling task has permissions to to use PTRACE_MODE_ATTACH_FSCREDS on the target task, so that we can ensure arbitrary apps do not change the timer slack for other apps. Signed-off-by: John Stultz <john.stultz@linaro.org> Acked-by: Kees Cook <keescook@chromium.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Oren Laadan <orenl@cellrox.com> Cc: Ruchi Kandoi <kandoiruchi@google.com> Cc: Rom Lemarchand <romlem@android.com> Cc: Android Kernel Team <kernel-team@android.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c67
1 files changed, 67 insertions, 0 deletions
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)