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

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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: Ruchi Kandoi <kandoiruchi@google.com>
This commit is contained in:
Ruchi Kandoi
2014-04-18 14:07:28 -07:00
parent a2acc58bc7
commit 37a591d407
2 changed files with 25 additions and 0 deletions
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6
include/uapi/linux/prctl.h
View File

@@ -149,6 +149,12 @@
#define PR_GET_TID_ADDRESS 40
/* 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 41
#define PR_SET_VMA 0x53564d41
# define PR_SET_VMA_ANON_NAME 0

19
kernel/sys.c
View File

@@ -44,6 +44,7 @@
#include <linux/ctype.h>
#include <linux/mm.h>
#include <linux/mempolicy.h>
#include <linux/sched.h>
#include <linux/compat.h>
#include <linux/syscalls.h>
@@ -2252,6 +2253,7 @@ 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;
@@ -2375,6 +2377,23 @@ 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;
}