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Date: Fri, 15 Oct 2010 17:38:50 -0700
From: John Stultz <john.stultz@...aro.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Richard Cochran <richardcochran@...il.com>,
Richard Cochran <richard.cochran@...cron.at>,
John Stultz <john.stultz@...aro.org>,
Alessandro Zummo <a.zummo@...ertech.it>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 1/6] [RFC] posix clocks: dynamic clock ids.
From: Richard Cochran <richardcochran@...il.com>
This patch augments the POSIX clock code to offer a dynamic clock
creation method. Instead of registering a hard coded clock ID, modules
may call create_posix_clock(), which returns a new clock ID.
Signed-off-by: Richard Cochran <richard.cochran@...cron.at>
This patch still has un-addressed lifetime issues pointed out by
Alan Cox. More work is needed here, but for now this provides the
functionality needed for the following patches.
Signed-off-by: John Stultz <john.stultz@...aro.org>
CC: Alessandro Zummo <a.zummo@...ertech.it>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Richard Cochran <richardcochran@...il.com>
---
include/linux/posix-timers.h | 7 ++++++-
include/linux/time.h | 2 ++
kernel/posix-timers.c | 41 ++++++++++++++++++++++++++++++++++-------
3 files changed, 42 insertions(+), 8 deletions(-)
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 3e23844..a9e601a 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -67,6 +67,7 @@ struct k_itimer {
};
struct k_clock {
+ clockid_t id;
int res; /* in nanoseconds */
int (*clock_getres) (const clockid_t which_clock, struct timespec *tp);
int (*clock_set) (const clockid_t which_clock, struct timespec * tp);
@@ -84,7 +85,11 @@ struct k_clock {
struct itimerspec * cur_setting);
};
-void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock);
+/* Regsiter a posix clock with a "well known" clock id. */
+int register_posix_clock(const clockid_t id, struct k_clock *clock);
+
+/* Create a new posix clock with a dynamic clock id. */
+clockid_t create_posix_clock(struct k_clock *clock);
/* error handlers for timer_create, nanosleep and settime */
int do_posix_clock_nonanosleep(const clockid_t, int flags, struct timespec *,
diff --git a/include/linux/time.h b/include/linux/time.h
index 9f15ac7..914c48d 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -299,6 +299,8 @@ struct itimerval {
#define CLOCKS_MASK (CLOCK_REALTIME | CLOCK_MONOTONIC)
#define CLOCKS_MONO CLOCK_MONOTONIC
+#define CLOCK_INVALID -1
+
/*
* The various flags for setting POSIX.1b interval timers:
*/
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 9ca4973..2f88d0b 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -132,6 +132,8 @@ static DEFINE_SPINLOCK(idr_lock);
*/
static struct k_clock posix_clocks[MAX_CLOCKS];
+static DECLARE_BITMAP(clocks_map, MAX_CLOCKS);
+static DEFINE_MUTEX(clocks_mux); /* protects 'posix_clocks' and 'clocks_map' */
/*
* These ones are defined below.
@@ -476,18 +478,43 @@ static struct pid *good_sigevent(sigevent_t * event)
return task_pid(rtn);
}
-void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
+int register_posix_clock(const clockid_t id, struct k_clock *clock)
{
- if ((unsigned) clock_id >= MAX_CLOCKS) {
- printk("POSIX clock register failed for clock_id %d\n",
- clock_id);
- return;
- }
+ struct k_clock *kc;
+ int err = 0;
- posix_clocks[clock_id] = *new_clock;
+ mutex_lock(&clocks_mux);
+ if (test_bit(id, clocks_map)) {
+ pr_err("clock_id %d already registered\n", id);
+ err = -EBUSY;
+ goto out;
+ }
+ kc = &posix_clocks[id];
+ *kc = *clock;
+ kc->id = id;
+ set_bit(id, clocks_map);
+out:
+ mutex_unlock(&clocks_mux);
+ return err;
}
EXPORT_SYMBOL_GPL(register_posix_clock);
+clockid_t create_posix_clock(struct k_clock *clock)
+{
+ clockid_t id;
+
+ mutex_lock(&clocks_mux);
+ id = find_first_zero_bit(clocks_map, MAX_CLOCKS);
+ mutex_unlock(&clocks_mux);
+
+ if (id < MAX_CLOCKS) {
+ register_posix_clock(id, clock);
+ return id;
+ }
+ return CLOCK_INVALID;
+}
+EXPORT_SYMBOL_GPL(create_posix_clock);
+
static struct k_itimer * alloc_posix_timer(void)
{
struct k_itimer *tmr;
--
1.6.0.4
--
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