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Commit f2902f90 authored by Ruchi Kandoi's avatar Ruchi Kandoi Committed by John Stultz
Browse files

prctl: adds PR_SET_TIMERSLACK_PID for setting timer slack of an arbitrary thread. 



Second argument is similar to PR_SET_TIMERSLACK, if non-zero then the
slack is set to that value otherwise sets it to the default for the thread.

Takes PID of the thread as the third argument.

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)

Change-Id: I744d451ff4e60dae69f38f53948ff36c51c14a3f
Signed-off-by: default avatarRuchi Kandoi <kandoiruchi@google.com>
parent e212fc78

include/uapi/linux/prctl.h

+6 −0
Original line number Diff line number Diff line
@@ -197,4 +197,10 @@ struct prctl_mm_map { 
# define PR_CAP_AMBIENT_LOWER		3

# define PR_CAP_AMBIENT_CLEAR_ALL	4



/* Sets the timerslack for arbitrary threads

 * arg2 slack value, 0 means "use default"

 * arg3 pid of the thread whose timer slack needs to be set

 */

#define PR_SET_TIMERSLACK_PID 47



#endif /* _LINUX_PRCTL_H */

kernel/sys.c

+18 −0
Original line number Diff line number Diff line
@@ -2076,6 +2076,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, 
		unsigned long, arg4, unsigned long, arg5)

{

	struct task_struct *me = current;

	struct task_struct *tsk;

	unsigned char comm[sizeof(me->comm)];

	long error;
@@ -2199,6 +2200,23 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, 
			else

				return -EINVAL;

			break;

		case PR_SET_TIMERSLACK_PID:

			rcu_read_lock();

			tsk = find_task_by_pid_ns((pid_t)arg3, &init_pid_ns);

			if (tsk == NULL) {

				rcu_read_unlock();

				return -EINVAL;

			}

			get_task_struct(tsk);

			rcu_read_unlock();

			if (arg2 <= 0)

				tsk->timer_slack_ns =

					tsk->default_timer_slack_ns;

			else

				tsk->timer_slack_ns = arg2;

			put_task_struct(tsk);

			error = 0;

			break;

		default:

			return -EINVAL;

		}