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Subject[PATCH 2/8] posix clocks: dynamic clock ids.
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@omicron.at>
---
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 abf61cc..08aa4da 100644
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -68,6 +68,7 @@ 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);
@@ -86,7 +87,11 @@ 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 446b566..67fba5c 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.
@@ -484,18 +486,43 @@ 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;
--
1.7.0.4


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