[RFC][PATCH 000/002] Add timestamp to process event connector message

[RFC][PATCH 000/002] Add timestamp to process event connector message

[Matt Helsley]

	This series of patches adds a timestamp field to the events sent
via the process event connector. The timestamp allows listeners to
accurately account the duration(s) between a process' events and offers
strong means with which to determine the order of events while also
avoiding the addition of per-task data.

Series:

getnstimestamp.patch
proc-events-timestamp.patch

	The first patch adds a new generic function, getnstimestamp(),
which gets an SMP-safe high-resolution monotonic timestamp.

	The second patch adds a timestamp field to the events sent via
the process event connector and fills the field using the new timestamp
function. It alters the size and layout of the event structure and hence
would break compatibility if not incorporated with the first release of
process events connector in a mainline kernel.

Cheers,
	-Matt Helsley

[RFC][PATCH 001/002] Add getnstimestamp function

[Matt Helsley]

There are several functions that might seem appropriate for a timestamp:

get_cycles()
current_kernel_time()
do_gettimeofday()
<read jiffies/jiffies_64>

Each has problems with combinations of SMP-safety, low resolution, and
monotonicity. This patch adds a new function that returns a monotonic SMP-safe
timestamp with nanosecond resolution where available.

Changes:
	Split timestamp into separate patch
	Moved to kernel/time.c
	Renamed to getnstimestamp
	Fixed unintended-pointer-arithmetic bug

Signed-off-by: Matt Helsley <matthltc@us.ibm.com>

--

Index: linux-2.6.15-rc5/kernel/time.c
===================================================================
--- linux-2.6.15-rc5.orig/kernel/time.c
+++ linux-2.6.15-rc5/kernel/time.c
@@ -562,10 +562,32 @@ void getnstimeofday(struct timespec *tv)
 	tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
 }
 EXPORT_SYMBOL_GPL(getnstimeofday);
 #endif
 
+void getnstimestamp(struct timespec *ts)
+{
+	unsigned int seq;
+	struct timespec wall2mono;
+
+	/* synchronize with settimeofday() changes */
+	do {
+		seq = read_seqbegin(&xtime_lock);
+		getnstimeofday(ts);
+		wall2mono = wall_to_monotonic;
+	} while(unlikely(read_seqretry(&xtime_lock, seq)));
+
+	/* adjust to monotonicaly-increasing values */
+	ts->tv_sec += wall2mono.tv_sec;
+	ts->tv_nsec += wall2mono.tv_nsec;
+	while (unlikely(ts->tv_nsec >= NSEC_PER_SEC)) {
+		ts->tv_nsec -= NSEC_PER_SEC;
+		ts->tv_sec++;
+	}
+}
+EXPORT_SYMBOL_GPL(getnstimestamp);
+
 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
  * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
  * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
  *
  * [For the Julian calendar (which was used in Russia before 1917,
Index: linux-2.6.15-rc5/include/linux/time.h
===================================================================
--- linux-2.6.15-rc5.orig/include/linux/time.h
+++ linux-2.6.15-rc5/include/linux/time.h
@@ -78,10 +78,11 @@ extern long do_utimes(char __user *filen
 struct itimerval;
 extern int do_setitimer(int which, struct itimerval *value,
 			struct itimerval *ovalue);
 extern int do_getitimer(int which, struct itimerval *value);
 extern void getnstimeofday(struct timespec *tv);
+extern void getnstimestamp(struct timespec *ts);
 
 extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
 
 /**
  * timespec_to_ns - Convert timespec to nanoseconds

[RFC][PATCH 002/002] Add timestamp field to process events

[Matt Helsley]

        This patch adds a timestamp field to the events sent via the process
event connector. The timestamp allows listeners to accurately account the
duration(s) between a process' events and offers strong means with which to
determine the order of events with respect to a given task while also avoiding
the addition of per-task data.

        This alters the size and layout of the event structure and hence would
break compatibility if process events connector as it stands in 2.6.15-rc2 were
released as a mainline kernel.

Signed-off-by: Matt Helsley <matthltc@us.ibm.com>

--

Index: linux-2.6.15-rc5/drivers/connector/cn_proc.c
===================================================================
--- linux-2.6.15-rc5.orig/drivers/connector/cn_proc.c
+++ linux-2.6.15-rc5/drivers/connector/cn_proc.c
@@ -54,10 +54,11 @@ void proc_fork_connector(struct task_str
 		return;
 
 	msg = (struct cn_msg*)buffer;
 	ev = (struct proc_event*)msg->data;
 	get_seq(&msg->seq, &ev->cpu);
+	getnstimestamp(&ev->timestamp);
 	ev->what = PROC_EVENT_FORK;
 	ev->event_data.fork.parent_pid = task->real_parent->pid;
 	ev->event_data.fork.parent_tgid = task->real_parent->tgid;
 	ev->event_data.fork.child_pid = task->pid;
 	ev->event_data.fork.child_tgid = task->tgid;
@@ -79,10 +80,11 @@ void proc_exec_connector(struct task_str
 		return;
 
 	msg = (struct cn_msg*)buffer;
 	ev = (struct proc_event*)msg->data;
 	get_seq(&msg->seq, &ev->cpu);
+	getnstimestamp(&ev->timestamp);
 	ev->what = PROC_EVENT_EXEC;
 	ev->event_data.exec.process_pid = task->pid;
 	ev->event_data.exec.process_tgid = task->tgid;
 
 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
@@ -112,10 +114,11 @@ void proc_id_connector(struct task_struc
 	   	ev->event_data.id.r.rgid = task->gid;
 	   	ev->event_data.id.e.egid = task->egid;
 	} else
 	     	return;
 	get_seq(&msg->seq, &ev->cpu);
+	getnstimestamp(&ev->timestamp);
 
 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
 	msg->ack = 0; /* not used */
 	msg->len = sizeof(*ev);
 	cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
@@ -131,10 +134,11 @@ void proc_exit_connector(struct task_str
 		return;
 
 	msg = (struct cn_msg*)buffer;
 	ev = (struct proc_event*)msg->data;
 	get_seq(&msg->seq, &ev->cpu);
+	getnstimestamp(&ev->timestamp);
 	ev->what = PROC_EVENT_EXIT;
 	ev->event_data.exit.process_pid = task->pid;
 	ev->event_data.exit.process_tgid = task->tgid;
 	ev->event_data.exit.exit_code = task->exit_code;
 	ev->event_data.exit.exit_signal = task->exit_signal;
@@ -163,10 +167,11 @@ static void cn_proc_ack(int err, int rcv
 		return;
 
 	msg = (struct cn_msg*)buffer;
 	ev = (struct proc_event*)msg->data;
 	msg->seq = rcvd_seq;
+	getnstimestamp(&ev->timestamp);
 	ev->cpu = -1;
 	ev->what = PROC_EVENT_NONE;
 	ev->event_data.ack.err = err;
 	memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
 	msg->ack = rcvd_ack + 1;
Index: linux-2.6.15-rc5/include/linux/cn_proc.h
===================================================================
--- linux-2.6.15-rc5.orig/include/linux/cn_proc.h
+++ linux-2.6.15-rc5/include/linux/cn_proc.h
@@ -24,10 +24,11 @@
 
 #ifndef CN_PROC_H
 #define CN_PROC_H
 
 #include <linux/types.h>
+#include <linux/time.h>
 #include <linux/connector.h>
 
 /*
  * Userspace sends this enum to register with the kernel that it is listening
  * for events on the connector.
@@ -63,10 +64,11 @@ struct proc_event {
 		/* "next" should be 0x00000400 */
 		/* "last" is the last process event: exit */
 		PROC_EVENT_EXIT = 0x80000000
 	} what;
 	__u32 cpu;
+	struct timespec timestamp;
 	union { /* must be last field of proc_event struct */
 		struct {
 			__u32 err;
 		} ack;