From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751930AbbFYXY4 (ORCPT ); Thu, 25 Jun 2015 19:24:56 -0400 Received: from mail-pd0-f169.google.com ([209.85.192.169]:35192 "EHLO mail-pd0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751555AbbFYXYs (ORCPT ); Thu, 25 Jun 2015 19:24:48 -0400 From: John Stultz To: lkml Cc: Ruchi Kandoi , Arjan van de Ven , Thomas Gleixner , Oren Laadan , Micha Kalfon , Rom Lemarchand , Android Kernel Team , John Stultz Subject: [RFC][PATCH] prctl: Add PR_SET_TIMERSLACK_PID for setting timer slack of an arbitrary thread. Date: Thu, 25 Jun 2015 16:24:42 -0700 Message-Id: <1435274682-9425-1-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ruchi Kandoi This patch has been in the Android tree for ahwile, and I've not seen it posted for review. Unfortunately the PR_SET_TIMERSLACK_PID value has collided many times w/ upstream (first w/ PR_SET_THP_DISABLE, and again w/ PR_MPX_ENABLE_MANAGEMENT). So to try to avoid further ABI trouble, I wanted to send this out for initial review to see if there were any major objections, or ideas for alternative approaches. Thoughts and feedback would be appreciated. thanks -john This patch 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) 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 interface checks check for CAP_SYS_NICE to make sure that arbitrary apps do not change the timer slack for other apps. Additional fixes from Ruchi and Micha Kalfon have been folded into this patch to make it easier to reivew. Cc: Arjan van de Ven Cc: Thomas Gleixner Cc: Oren Laadan Cc: Micha Kalfon Cc: Ruchi Kandoi Cc: Rom Lemarchand Cc: Android Kernel Team Signed-off-by: Ruchi Kandoi [jstultz: * Folded in CAP_SYS_NICE check from Ruchi. * Folded in fix misplaced PR_SET_TIMERSLACK_PID case fix from Micha. * Folded in make PR_SET_TIMERSLACK_PID pid namespace aware fix from Micha. * Changed PR_SET_TIMERSLACK_PID so it didn't collide with already upstream prctrl values. * Reworked commit message.] Signed-off-by: John Stultz --- include/uapi/linux/prctl.h | 7 +++++++ kernel/sys.c | 24 ++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 31891d9..7086be4 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -187,6 +187,13 @@ struct prctl_mm_map { #define PR_SET_FP_MODE 45 #define PR_GET_FP_MODE 46 + +/* 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 + # define PR_FP_MODE_FR (1 << 0) /* 64b FP registers */ # define PR_FP_MODE_FRE (1 << 1) /* 32b compatibility */ diff --git a/kernel/sys.c b/kernel/sys.c index 8571296..75b32f0 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -41,6 +41,9 @@ #include #include #include +#include +#include +#include #include #include @@ -2053,6 +2056,7 @@ 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; @@ -2195,6 +2199,26 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_GET_TID_ADDRESS: error = prctl_get_tid_address(me, (int __user **)arg2); break; + case PR_SET_TIMERSLACK_PID: + if (task_pid_vnr(current) != (pid_t)arg3 && + !capable(CAP_SYS_NICE)) + return -EPERM; + rcu_read_lock(); + tsk = find_task_by_vpid((pid_t)arg3); + 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; case PR_SET_CHILD_SUBREAPER: me->signal->is_child_subreaper = !!arg2; break; -- 1.9.1