linux/drivers/oprofile/event_buffer.c
Arjan van de Ven d54b1fdb1d [PATCH] mark struct file_operations const 5
Many struct file_operations in the kernel can be "const".  Marking them const
moves these to the .rodata section, which avoids false sharing with potential
dirty data.  In addition it'll catch accidental writes at compile time to
these shared resources.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-12 09:48:45 -08:00

188 lines
3.9 KiB
C

/**
* @file event_buffer.c
*
* @remark Copyright 2002 OProfile authors
* @remark Read the file COPYING
*
* @author John Levon <levon@movementarian.org>
*
* This is the global event buffer that the user-space
* daemon reads from. The event buffer is an untyped array
* of unsigned longs. Entries are prefixed by the
* escape value ESCAPE_CODE followed by an identifying code.
*/
#include <linux/vmalloc.h>
#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/capability.h>
#include <linux/dcookies.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#include "oprof.h"
#include "event_buffer.h"
#include "oprofile_stats.h"
DEFINE_MUTEX(buffer_mutex);
static unsigned long buffer_opened;
static DECLARE_WAIT_QUEUE_HEAD(buffer_wait);
static unsigned long * event_buffer;
static unsigned long buffer_size;
static unsigned long buffer_watershed;
static size_t buffer_pos;
/* atomic_t because wait_event checks it outside of buffer_mutex */
static atomic_t buffer_ready = ATOMIC_INIT(0);
/* Add an entry to the event buffer. When we
* get near to the end we wake up the process
* sleeping on the read() of the file.
*/
void add_event_entry(unsigned long value)
{
if (buffer_pos == buffer_size) {
atomic_inc(&oprofile_stats.event_lost_overflow);
return;
}
event_buffer[buffer_pos] = value;
if (++buffer_pos == buffer_size - buffer_watershed) {
atomic_set(&buffer_ready, 1);
wake_up(&buffer_wait);
}
}
/* Wake up the waiting process if any. This happens
* on "echo 0 >/dev/oprofile/enable" so the daemon
* processes the data remaining in the event buffer.
*/
void wake_up_buffer_waiter(void)
{
mutex_lock(&buffer_mutex);
atomic_set(&buffer_ready, 1);
wake_up(&buffer_wait);
mutex_unlock(&buffer_mutex);
}
int alloc_event_buffer(void)
{
int err = -ENOMEM;
spin_lock(&oprofilefs_lock);
buffer_size = fs_buffer_size;
buffer_watershed = fs_buffer_watershed;
spin_unlock(&oprofilefs_lock);
if (buffer_watershed >= buffer_size)
return -EINVAL;
event_buffer = vmalloc(sizeof(unsigned long) * buffer_size);
if (!event_buffer)
goto out;
err = 0;
out:
return err;
}
void free_event_buffer(void)
{
vfree(event_buffer);
}
static int event_buffer_open(struct inode * inode, struct file * file)
{
int err = -EPERM;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (test_and_set_bit(0, &buffer_opened))
return -EBUSY;
/* Register as a user of dcookies
* to ensure they persist for the lifetime of
* the open event file
*/
err = -EINVAL;
file->private_data = dcookie_register();
if (!file->private_data)
goto out;
if ((err = oprofile_setup()))
goto fail;
/* NB: the actual start happens from userspace
* echo 1 >/dev/oprofile/enable
*/
return 0;
fail:
dcookie_unregister(file->private_data);
out:
clear_bit(0, &buffer_opened);
return err;
}
static int event_buffer_release(struct inode * inode, struct file * file)
{
oprofile_stop();
oprofile_shutdown();
dcookie_unregister(file->private_data);
buffer_pos = 0;
atomic_set(&buffer_ready, 0);
clear_bit(0, &buffer_opened);
return 0;
}
static ssize_t event_buffer_read(struct file * file, char __user * buf,
size_t count, loff_t * offset)
{
int retval = -EINVAL;
size_t const max = buffer_size * sizeof(unsigned long);
/* handling partial reads is more trouble than it's worth */
if (count != max || *offset)
return -EINVAL;
wait_event_interruptible(buffer_wait, atomic_read(&buffer_ready));
if (signal_pending(current))
return -EINTR;
/* can't currently happen */
if (!atomic_read(&buffer_ready))
return -EAGAIN;
mutex_lock(&buffer_mutex);
atomic_set(&buffer_ready, 0);
retval = -EFAULT;
count = buffer_pos * sizeof(unsigned long);
if (copy_to_user(buf, event_buffer, count))
goto out;
retval = count;
buffer_pos = 0;
out:
mutex_unlock(&buffer_mutex);
return retval;
}
const struct file_operations event_buffer_fops = {
.open = event_buffer_open,
.release = event_buffer_release,
.read = event_buffer_read,
};