- moving default_timer_slack_ns from per-task field to global variable
controlled via sysctl() in [0..1000000] range (usecs) provides some
more system-wide control beyond per-task prctl();
- task_time_slack() should be used to get default timer slack if no
special requirements exists.
Signed-off-by: Dmitry Antipov <dmitry.anti...@linaro.org>
---
include/linux/hrtimer.h | 1 +
include/linux/sched.h | 11 ++++++++---
kernel/fork.c | 3 ---
kernel/futex.c | 4 ++--
kernel/hrtimer.c | 10 +++++++---
kernel/sys.c | 3 ++-
kernel/sysctl.c | 10 ++++++++++
7 files changed, 30 insertions(+), 12 deletions(-)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index fd0dc30..855d45e 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -323,6 +323,7 @@ extern ktime_t ktime_get_monotonic_offset(void);
DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
+extern int default_timer_slack_ns;
/* Exported timer functions: */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2234985..4f475aa 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1551,11 +1551,11 @@ struct task_struct {
struct latency_record latency_record[LT_SAVECOUNT];
#endif
/*
- * time slack values; these are used to round up poll() and
- * select() etc timeout values. These are in nanoseconds.
+ * High-resolution timer slack value, in nanoseconds.
+ * Used to round up poll()/select(), nanosleep, futex
+ * waiting, etc. timeout values for non-realtime tasks.
*/
unsigned long timer_slack_ns;
- unsigned long default_timer_slack_ns;
struct list_head *scm_work_list;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -2622,6 +2622,11 @@ static inline int spin_needbreak(spinlock_t *lock)
#endif
}
+static inline unsigned long task_timer_slack(struct task_struct *tsk)
+{
+ return rt_task(tsk) ? 0 : tsk->timer_slack_ns;
+}
+
/*
* Thread group CPU time accounting.
*/
diff --git a/kernel/fork.c b/kernel/fork.c
index 051f090..b0e8f63 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1144,9 +1144,6 @@ static struct task_struct *copy_process(unsigned long
clone_flags,
#if defined(SPLIT_RSS_COUNTING)
memset(&p->rss_stat, 0, sizeof(p->rss_stat));
#endif
-
- p->default_timer_slack_ns = current->timer_slack_ns;
-
task_io_accounting_init(&p->ioac);
acct_clear_integrals(p);
diff --git a/kernel/futex.c b/kernel/futex.c
index 1614be2..a0d302d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1887,7 +1887,7 @@ static int futex_wait(u32 __user *uaddr, unsigned int
flags, u32 val,
HRTIMER_MODE_ABS);
hrtimer_init_sleeper(to, current);
hrtimer_set_expires_range_ns(&to->timer, *abs_time,
- current->timer_slack_ns);
+ task_timer_slack(current));
}
retry:
@@ -2281,7 +2281,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr,
unsigned int flags,
HRTIMER_MODE_ABS);
hrtimer_init_sleeper(to, current);
hrtimer_set_expires_range_ns(&to->timer, *abs_time,
- current->timer_slack_ns);
+ task_timer_slack(current));
}
/*
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index ae34bf5..0704559 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -51,6 +51,12 @@
#include <trace/events/timer.h>
/*
+ * Default hrtimer slack value, in nanoseconds. May be
+ * changed via sysctl within [0..1000000] range.
+ */
+int default_timer_slack_ns = 50000;
+
+/*
* The timer bases:
*
* There are more clockids then hrtimer bases. Thus, we index
@@ -1564,9 +1570,7 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct
timespec __user *rmtp,
int ret = 0;
unsigned long slack;
- slack = current->timer_slack_ns;
- if (rt_task(current))
- slack = 0;
+ slack = task_timer_slack(current);
hrtimer_init_on_stack(&t.timer, clockid, mode);
hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack);
diff --git a/kernel/sys.c b/kernel/sys.c
index 4070153..db36543 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -22,6 +22,7 @@
#include <linux/device.h>
#include <linux/key.h>
#include <linux/times.h>
+#include <linux/hrtimer.h>
#include <linux/posix-timers.h>
#include <linux/security.h>
#include <linux/dcookies.h>
@@ -1919,7 +1920,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2,
unsigned long, arg3,
case PR_SET_TIMERSLACK:
if (arg2 <= 0)
current->timer_slack_ns =
- current->default_timer_slack_ns;
+ default_timer_slack_ns;
else
current->timer_slack_ns = arg2;
error = 0;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f487f25..c9a731b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -122,6 +122,7 @@ static int __maybe_unused two = 2;
static int __maybe_unused three = 3;
static unsigned long one_ul = 1;
static int one_hundred = 100;
+static int million = 1000000;
#ifdef CONFIG_PRINTK
static int ten_thousand = 10000;
#endif
@@ -1004,6 +1005,15 @@ static struct ctl_table kern_table[] = {
.proc_handler = proc_dointvec,
},
#endif
+ {
+ .procname = "timer_slack",
+ .data = &default_timer_slack_ns,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &zero,
+ .extra2 = &million,
+ },
{ }
};
--
1.7.7.5
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