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2d21a29fb6
The oprofilefs_lock can be taken in atomic context (in profiling interrupts) and therefore cannot cannot be preempted on -rt - annotate it. In mainline this change documents the low level nature of the lock - otherwise there's no functional difference. Lockdep and Sparse checking will work as usual. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
210 lines
4.5 KiB
C
210 lines
4.5 KiB
C
/**
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* @file event_buffer.c
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*
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* @remark Copyright 2002 OProfile authors
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* @remark Read the file COPYING
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*
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* @author John Levon <levon@movementarian.org>
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*
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* This is the global event buffer that the user-space
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* daemon reads from. The event buffer is an untyped array
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* of unsigned longs. Entries are prefixed by the
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* escape value ESCAPE_CODE followed by an identifying code.
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*/
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#include <linux/vmalloc.h>
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#include <linux/oprofile.h>
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#include <linux/sched.h>
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#include <linux/capability.h>
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#include <linux/dcookies.h>
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#include <linux/fs.h>
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#include <asm/uaccess.h>
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#include "oprof.h"
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#include "event_buffer.h"
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#include "oprofile_stats.h"
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DEFINE_MUTEX(buffer_mutex);
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static unsigned long buffer_opened;
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static DECLARE_WAIT_QUEUE_HEAD(buffer_wait);
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static unsigned long *event_buffer;
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static unsigned long buffer_size;
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static unsigned long buffer_watershed;
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static size_t buffer_pos;
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/* atomic_t because wait_event checks it outside of buffer_mutex */
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static atomic_t buffer_ready = ATOMIC_INIT(0);
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/*
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* Add an entry to the event buffer. When we get near to the end we
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* wake up the process sleeping on the read() of the file. To protect
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* the event_buffer this function may only be called when buffer_mutex
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* is set.
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*/
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void add_event_entry(unsigned long value)
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{
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/*
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* This shouldn't happen since all workqueues or handlers are
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* canceled or flushed before the event buffer is freed.
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*/
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if (!event_buffer) {
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WARN_ON_ONCE(1);
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return;
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}
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if (buffer_pos == buffer_size) {
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atomic_inc(&oprofile_stats.event_lost_overflow);
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return;
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}
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event_buffer[buffer_pos] = value;
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if (++buffer_pos == buffer_size - buffer_watershed) {
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atomic_set(&buffer_ready, 1);
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wake_up(&buffer_wait);
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}
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}
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/* Wake up the waiting process if any. This happens
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* on "echo 0 >/dev/oprofile/enable" so the daemon
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* processes the data remaining in the event buffer.
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*/
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void wake_up_buffer_waiter(void)
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{
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mutex_lock(&buffer_mutex);
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atomic_set(&buffer_ready, 1);
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wake_up(&buffer_wait);
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mutex_unlock(&buffer_mutex);
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}
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int alloc_event_buffer(void)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&oprofilefs_lock, flags);
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buffer_size = oprofile_buffer_size;
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buffer_watershed = oprofile_buffer_watershed;
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raw_spin_unlock_irqrestore(&oprofilefs_lock, flags);
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if (buffer_watershed >= buffer_size)
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return -EINVAL;
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buffer_pos = 0;
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event_buffer = vmalloc(sizeof(unsigned long) * buffer_size);
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if (!event_buffer)
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return -ENOMEM;
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return 0;
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}
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void free_event_buffer(void)
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{
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mutex_lock(&buffer_mutex);
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vfree(event_buffer);
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buffer_pos = 0;
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event_buffer = NULL;
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mutex_unlock(&buffer_mutex);
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}
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static int event_buffer_open(struct inode *inode, struct file *file)
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{
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int err = -EPERM;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if (test_and_set_bit_lock(0, &buffer_opened))
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return -EBUSY;
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/* Register as a user of dcookies
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* to ensure they persist for the lifetime of
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* the open event file
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*/
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err = -EINVAL;
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file->private_data = dcookie_register();
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if (!file->private_data)
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goto out;
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if ((err = oprofile_setup()))
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goto fail;
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/* NB: the actual start happens from userspace
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* echo 1 >/dev/oprofile/enable
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*/
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return nonseekable_open(inode, file);
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fail:
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dcookie_unregister(file->private_data);
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out:
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__clear_bit_unlock(0, &buffer_opened);
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return err;
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}
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static int event_buffer_release(struct inode *inode, struct file *file)
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{
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oprofile_stop();
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oprofile_shutdown();
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dcookie_unregister(file->private_data);
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buffer_pos = 0;
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atomic_set(&buffer_ready, 0);
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__clear_bit_unlock(0, &buffer_opened);
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return 0;
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}
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static ssize_t event_buffer_read(struct file *file, char __user *buf,
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size_t count, loff_t *offset)
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{
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int retval = -EINVAL;
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size_t const max = buffer_size * sizeof(unsigned long);
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/* handling partial reads is more trouble than it's worth */
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if (count != max || *offset)
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return -EINVAL;
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wait_event_interruptible(buffer_wait, atomic_read(&buffer_ready));
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if (signal_pending(current))
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return -EINTR;
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/* can't currently happen */
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if (!atomic_read(&buffer_ready))
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return -EAGAIN;
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mutex_lock(&buffer_mutex);
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/* May happen if the buffer is freed during pending reads. */
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if (!event_buffer) {
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retval = -EINTR;
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goto out;
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}
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atomic_set(&buffer_ready, 0);
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retval = -EFAULT;
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count = buffer_pos * sizeof(unsigned long);
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if (copy_to_user(buf, event_buffer, count))
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goto out;
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retval = count;
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buffer_pos = 0;
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out:
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mutex_unlock(&buffer_mutex);
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return retval;
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}
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const struct file_operations event_buffer_fops = {
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.open = event_buffer_open,
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.release = event_buffer_release,
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.read = event_buffer_read,
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.llseek = no_llseek,
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};
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