On Tue, 2013-04-02 at 17:19 +0100, John Stultz wrote:
> But if we're going to have to do
> this via a clockid, I'm going to want it to be done via a dynamic posix
> clockid, so its clear its tightly tied with perf and not considered a
> generic interface (and I can clearly point folks having problems to the
> perf maintainers ;).
Ok, so how about the code below?
There are two distinct parts of the "solution":
1. The dynamic posix clock, as you suggested. Then one can get the perf
timestamp by doing:
clock_fd = open("/dev/perf-clock", O_RDONLY);
clock_gettime(FD_TO_CLOCKID(clock_fd), &ts)
2. A sort-of-hack in the get_posix_clock() function making it possible
to do the same using the perf event file descriptor, eg.:
fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
clock_gettime(FD_TO_CLOCKID(fd), &ts)
Any (either strong or not) opinions?
Pawel
8<--------------
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index e47ee46..b2127e3 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -52,6 +52,7 @@ struct perf_guest_info_callbacks {
#include <linux/atomic.h>
#include <linux/sysfs.h>
#include <linux/perf_regs.h>
+#include <linux/posix-clock.h>
#include <asm/local.h>
struct perf_callchain_entry {
@@ -845,4 +846,6 @@ _name##_show(struct device *dev,
\
\
static struct device_attribute format_attr_##_name = __ATTR_RO(_name)
+struct posix_clock *perf_get_posix_clock(struct file *fp);
+
#endif /* _LINUX_PERF_EVENT_H */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index b0cd865..534cb43 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7446,6 +7446,49 @@ unlock:
}
device_initcall(perf_event_sysfs_init);
+static int perf_posix_clock_getres(struct posix_clock *pc, struct timespec *tp)
+{
+ *tp = ns_to_timespec(TICK_NSEC);
+ return 0;
+}
+
+static int perf_posix_clock_gettime(struct posix_clock *pc, struct timespec
*tp)
+{
+ *tp = ns_to_timespec(perf_clock());
+ return 0;
+}
+
+static const struct posix_clock_operations perf_posix_clock_ops = {
+ .clock_getres = perf_posix_clock_getres,
+ .clock_gettime = perf_posix_clock_gettime,
+};
+
+static struct posix_clock perf_posix_clock;
+
+struct posix_clock *perf_get_posix_clock(struct file *fp)
+{
+ if (!fp || fp->f_op != &perf_fops)
+ return NULL;
+
+ down_read(&perf_posix_clock.rwsem);
+
+ return &perf_posix_clock;
+}
+
+static int __init perf_posix_clock_init(void)
+{
+ dev_t devt;
+ int ret;
+
+ ret = alloc_chrdev_region(&devt, 0, 1, "perf-clock");
+ if (ret)
+ return ret;
+
+ perf_posix_clock.ops = perf_posix_clock_ops;
+ return posix_clock_register(&perf_posix_clock, devt);
+}
+device_initcall(perf_posix_clock_init);
+
#ifdef CONFIG_CGROUP_PERF
static struct cgroup_subsys_state *perf_cgroup_css_alloc(struct cgroup *cont)
{
diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
index ce033c7..e2a40a5 100644
--- a/kernel/time/posix-clock.c
+++ b/kernel/time/posix-clock.c
@@ -20,6 +20,7 @@
#include <linux/device.h>
#include <linux/export.h>
#include <linux/file.h>
+#include <linux/perf_event.h>
#include <linux/posix-clock.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
@@ -249,16 +250,21 @@ struct posix_clock_desc {
static int get_clock_desc(const clockid_t id, struct posix_clock_desc *cd)
{
struct file *fp = fget(CLOCKID_TO_FD(id));
+ struct posix_clock *perf_clk = NULL;
int err = -EINVAL;
if (!fp)
return err;
- if (fp->f_op->open != posix_clock_open || !fp->private_data)
+#if defined(CONFIG_PERF_EVENTS)
+ perf_clk = perf_get_posix_clock(fp);
+#endif
+ if ((fp->f_op->open != posix_clock_open || !fp->private_data) &&
+ !perf_clk)
goto out;
cd->fp = fp;
- cd->clk = get_posix_clock(fp);
+ cd->clk = perf_clk ? perf_clk : get_posix_clock(fp);
err = cd->clk ? 0 : -ENODEV;
out:
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
