linux/drivers/oprofile/oprof.c
Robert Richter 7df01d96b2 oprofile: disable write access to oprofilefs while profiler is running
Oprofile counters are setup when profiling is disabled. Thus, writing
to oprofilefs has no immediate effect. Changes are updated only after
oprofile is reenabled.

To keep userland and kernel states synchronized, we now allow
configuration of oprofile only if profiling is disabled.  In this case
it checks if the profiler is running and then disables write access to
oprofilefs by returning -EBUSY. The change should be backward
compatible with current oprofile userland daemon.

Acked-by: Maynard Johnson <maynardj@us.ibm.com>
Cc: William Cohen <wcohen@redhat.com>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>
2010-10-12 17:25:06 +02:00

274 lines
4.8 KiB
C

/**
* @file oprof.c
*
* @remark Copyright 2002 OProfile authors
* @remark Read the file COPYING
*
* @author John Levon <levon@movementarian.org>
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/oprofile.h>
#include <linux/moduleparam.h>
#include <linux/workqueue.h>
#include <linux/time.h>
#include <asm/mutex.h>
#include "oprof.h"
#include "event_buffer.h"
#include "cpu_buffer.h"
#include "buffer_sync.h"
#include "oprofile_stats.h"
struct oprofile_operations oprofile_ops;
unsigned long oprofile_started;
unsigned long oprofile_backtrace_depth;
static unsigned long is_setup;
static DEFINE_MUTEX(start_mutex);
/* timer
0 - use performance monitoring hardware if available
1 - use the timer int mechanism regardless
*/
static int timer = 0;
int oprofile_setup(void)
{
int err;
mutex_lock(&start_mutex);
if ((err = alloc_cpu_buffers()))
goto out;
if ((err = alloc_event_buffer()))
goto out1;
if (oprofile_ops.setup && (err = oprofile_ops.setup()))
goto out2;
/* Note even though this starts part of the
* profiling overhead, it's necessary to prevent
* us missing task deaths and eventually oopsing
* when trying to process the event buffer.
*/
if (oprofile_ops.sync_start) {
int sync_ret = oprofile_ops.sync_start();
switch (sync_ret) {
case 0:
goto post_sync;
case 1:
goto do_generic;
case -1:
goto out3;
default:
goto out3;
}
}
do_generic:
if ((err = sync_start()))
goto out3;
post_sync:
is_setup = 1;
mutex_unlock(&start_mutex);
return 0;
out3:
if (oprofile_ops.shutdown)
oprofile_ops.shutdown();
out2:
free_event_buffer();
out1:
free_cpu_buffers();
out:
mutex_unlock(&start_mutex);
return err;
}
#ifdef CONFIG_OPROFILE_EVENT_MULTIPLEX
static void switch_worker(struct work_struct *work);
static DECLARE_DELAYED_WORK(switch_work, switch_worker);
static void start_switch_worker(void)
{
if (oprofile_ops.switch_events)
schedule_delayed_work(&switch_work, oprofile_time_slice);
}
static void stop_switch_worker(void)
{
cancel_delayed_work_sync(&switch_work);
}
static void switch_worker(struct work_struct *work)
{
if (oprofile_ops.switch_events())
return;
atomic_inc(&oprofile_stats.multiplex_counter);
start_switch_worker();
}
/* User inputs in ms, converts to jiffies */
int oprofile_set_timeout(unsigned long val_msec)
{
int err = 0;
unsigned long time_slice;
mutex_lock(&start_mutex);
if (oprofile_started) {
err = -EBUSY;
goto out;
}
if (!oprofile_ops.switch_events) {
err = -EINVAL;
goto out;
}
time_slice = msecs_to_jiffies(val_msec);
if (time_slice == MAX_JIFFY_OFFSET) {
err = -EINVAL;
goto out;
}
oprofile_time_slice = time_slice;
out:
mutex_unlock(&start_mutex);
return err;
}
#else
static inline void start_switch_worker(void) { }
static inline void stop_switch_worker(void) { }
#endif
/* Actually start profiling (echo 1>/dev/oprofile/enable) */
int oprofile_start(void)
{
int err = -EINVAL;
mutex_lock(&start_mutex);
if (!is_setup)
goto out;
err = 0;
if (oprofile_started)
goto out;
oprofile_reset_stats();
if ((err = oprofile_ops.start()))
goto out;
start_switch_worker();
oprofile_started = 1;
out:
mutex_unlock(&start_mutex);
return err;
}
/* echo 0>/dev/oprofile/enable */
void oprofile_stop(void)
{
mutex_lock(&start_mutex);
if (!oprofile_started)
goto out;
oprofile_ops.stop();
oprofile_started = 0;
stop_switch_worker();
/* wake up the daemon to read what remains */
wake_up_buffer_waiter();
out:
mutex_unlock(&start_mutex);
}
void oprofile_shutdown(void)
{
mutex_lock(&start_mutex);
if (oprofile_ops.sync_stop) {
int sync_ret = oprofile_ops.sync_stop();
switch (sync_ret) {
case 0:
goto post_sync;
case 1:
goto do_generic;
default:
goto post_sync;
}
}
do_generic:
sync_stop();
post_sync:
if (oprofile_ops.shutdown)
oprofile_ops.shutdown();
is_setup = 0;
free_event_buffer();
free_cpu_buffers();
mutex_unlock(&start_mutex);
}
int oprofile_set_ulong(unsigned long *addr, unsigned long val)
{
int err = -EBUSY;
mutex_lock(&start_mutex);
if (!oprofile_started) {
*addr = val;
err = 0;
}
mutex_unlock(&start_mutex);
return err;
}
static int __init oprofile_init(void)
{
int err;
err = oprofile_arch_init(&oprofile_ops);
if (err < 0 || timer) {
printk(KERN_INFO "oprofile: using timer interrupt.\n");
err = oprofile_timer_init(&oprofile_ops);
if (err)
return err;
}
return oprofilefs_register();
}
static void __exit oprofile_exit(void)
{
oprofile_timer_exit();
oprofilefs_unregister();
oprofile_arch_exit();
}
module_init(oprofile_init);
module_exit(oprofile_exit);
module_param_named(timer, timer, int, 0644);
MODULE_PARM_DESC(timer, "force use of timer interrupt");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("John Levon <levon@movementarian.org>");
MODULE_DESCRIPTION("OProfile system profiler");