kernel-fxtec-pro1x/fs/relayfs/relay.c
Tom Zanussi fd30fc3256 [PATCH] relayfs: remove warning printk() in relay_switch_subbuf()
There's currently a diagnostic printk in relay_switch_subbuf() meant as
a warning if you accidentally try to log an event larger than the
sub-buffer size.

The problem is if this happens while logging from somewhere it's not
safe to be doing printks, such as in the scheduler, you can end up with
a deadlock.  This patch removes the warning from relay_switch_subbuf()
and instead prints some diagnostic info when the channel is closed.

Thanks to Mathieu Desnoyers for pointing out the problem and
suggesting a fix.

Signed-off-by: Tom Zanussi <zanussi@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-20 17:33:22 -08:00

435 lines
10 KiB
C

/*
* Public API and common code for RelayFS.
*
* See Documentation/filesystems/relayfs.txt for an overview of relayfs.
*
* Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
* Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
*
* This file is released under the GPL.
*/
#include <linux/errno.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/relayfs_fs.h>
#include "relay.h"
#include "buffers.h"
/**
* relay_buf_empty - boolean, is the channel buffer empty?
* @buf: channel buffer
*
* Returns 1 if the buffer is empty, 0 otherwise.
*/
int relay_buf_empty(struct rchan_buf *buf)
{
return (buf->subbufs_produced - buf->subbufs_consumed) ? 0 : 1;
}
/**
* relay_buf_full - boolean, is the channel buffer full?
* @buf: channel buffer
*
* Returns 1 if the buffer is full, 0 otherwise.
*/
int relay_buf_full(struct rchan_buf *buf)
{
size_t ready = buf->subbufs_produced - buf->subbufs_consumed;
return (ready >= buf->chan->n_subbufs) ? 1 : 0;
}
/*
* High-level relayfs kernel API and associated functions.
*/
/*
* rchan_callback implementations defining default channel behavior. Used
* in place of corresponding NULL values in client callback struct.
*/
/*
* subbuf_start() default callback. Does nothing.
*/
static int subbuf_start_default_callback (struct rchan_buf *buf,
void *subbuf,
void *prev_subbuf,
size_t prev_padding)
{
if (relay_buf_full(buf))
return 0;
return 1;
}
/*
* buf_mapped() default callback. Does nothing.
*/
static void buf_mapped_default_callback(struct rchan_buf *buf,
struct file *filp)
{
}
/*
* buf_unmapped() default callback. Does nothing.
*/
static void buf_unmapped_default_callback(struct rchan_buf *buf,
struct file *filp)
{
}
/* relay channel default callbacks */
static struct rchan_callbacks default_channel_callbacks = {
.subbuf_start = subbuf_start_default_callback,
.buf_mapped = buf_mapped_default_callback,
.buf_unmapped = buf_unmapped_default_callback,
};
/**
* wakeup_readers - wake up readers waiting on a channel
* @private: the channel buffer
*
* This is the work function used to defer reader waking. The
* reason waking is deferred is that calling directly from write
* causes problems if you're writing from say the scheduler.
*/
static void wakeup_readers(void *private)
{
struct rchan_buf *buf = private;
wake_up_interruptible(&buf->read_wait);
}
/**
* __relay_reset - reset a channel buffer
* @buf: the channel buffer
* @init: 1 if this is a first-time initialization
*
* See relay_reset for description of effect.
*/
static inline void __relay_reset(struct rchan_buf *buf, unsigned int init)
{
size_t i;
if (init) {
init_waitqueue_head(&buf->read_wait);
kref_init(&buf->kref);
INIT_WORK(&buf->wake_readers, NULL, NULL);
} else {
cancel_delayed_work(&buf->wake_readers);
flush_scheduled_work();
}
buf->subbufs_produced = 0;
buf->subbufs_consumed = 0;
buf->bytes_consumed = 0;
buf->finalized = 0;
buf->data = buf->start;
buf->offset = 0;
for (i = 0; i < buf->chan->n_subbufs; i++)
buf->padding[i] = 0;
buf->chan->cb->subbuf_start(buf, buf->data, NULL, 0);
}
/**
* relay_reset - reset the channel
* @chan: the channel
*
* This has the effect of erasing all data from all channel buffers
* and restarting the channel in its initial state. The buffers
* are not freed, so any mappings are still in effect.
*
* NOTE: Care should be taken that the channel isn't actually
* being used by anything when this call is made.
*/
void relay_reset(struct rchan *chan)
{
unsigned int i;
if (!chan)
return;
for (i = 0; i < NR_CPUS; i++) {
if (!chan->buf[i])
continue;
__relay_reset(chan->buf[i], 0);
}
}
/**
* relay_open_buf - create a new channel buffer in relayfs
*
* Internal - used by relay_open().
*/
static struct rchan_buf *relay_open_buf(struct rchan *chan,
const char *filename,
struct dentry *parent)
{
struct rchan_buf *buf;
struct dentry *dentry;
/* Create file in fs */
dentry = relayfs_create_file(filename, parent, S_IRUSR, chan);
if (!dentry)
return NULL;
buf = RELAYFS_I(dentry->d_inode)->buf;
buf->dentry = dentry;
__relay_reset(buf, 1);
return buf;
}
/**
* relay_close_buf - close a channel buffer
* @buf: channel buffer
*
* Marks the buffer finalized and restores the default callbacks.
* The channel buffer and channel buffer data structure are then freed
* automatically when the last reference is given up.
*/
static inline void relay_close_buf(struct rchan_buf *buf)
{
buf->finalized = 1;
buf->chan->cb = &default_channel_callbacks;
cancel_delayed_work(&buf->wake_readers);
flush_scheduled_work();
kref_put(&buf->kref, relay_remove_buf);
}
static inline void setup_callbacks(struct rchan *chan,
struct rchan_callbacks *cb)
{
if (!cb) {
chan->cb = &default_channel_callbacks;
return;
}
if (!cb->subbuf_start)
cb->subbuf_start = subbuf_start_default_callback;
if (!cb->buf_mapped)
cb->buf_mapped = buf_mapped_default_callback;
if (!cb->buf_unmapped)
cb->buf_unmapped = buf_unmapped_default_callback;
chan->cb = cb;
}
/**
* relay_open - create a new relayfs channel
* @base_filename: base name of files to create
* @parent: dentry of parent directory, NULL for root directory
* @subbuf_size: size of sub-buffers
* @n_subbufs: number of sub-buffers
* @cb: client callback functions
*
* Returns channel pointer if successful, NULL otherwise.
*
* Creates a channel buffer for each cpu using the sizes and
* attributes specified. The created channel buffer files
* will be named base_filename0...base_filenameN-1. File
* permissions will be S_IRUSR.
*/
struct rchan *relay_open(const char *base_filename,
struct dentry *parent,
size_t subbuf_size,
size_t n_subbufs,
struct rchan_callbacks *cb)
{
unsigned int i;
struct rchan *chan;
char *tmpname;
if (!base_filename)
return NULL;
if (!(subbuf_size && n_subbufs))
return NULL;
chan = kcalloc(1, sizeof(struct rchan), GFP_KERNEL);
if (!chan)
return NULL;
chan->version = RELAYFS_CHANNEL_VERSION;
chan->n_subbufs = n_subbufs;
chan->subbuf_size = subbuf_size;
chan->alloc_size = FIX_SIZE(subbuf_size * n_subbufs);
setup_callbacks(chan, cb);
kref_init(&chan->kref);
tmpname = kmalloc(NAME_MAX + 1, GFP_KERNEL);
if (!tmpname)
goto free_chan;
for_each_online_cpu(i) {
sprintf(tmpname, "%s%d", base_filename, i);
chan->buf[i] = relay_open_buf(chan, tmpname, parent);
chan->buf[i]->cpu = i;
if (!chan->buf[i])
goto free_bufs;
}
kfree(tmpname);
return chan;
free_bufs:
for (i = 0; i < NR_CPUS; i++) {
if (!chan->buf[i])
break;
relay_close_buf(chan->buf[i]);
}
kfree(tmpname);
free_chan:
kref_put(&chan->kref, relay_destroy_channel);
return NULL;
}
/**
* relay_switch_subbuf - switch to a new sub-buffer
* @buf: channel buffer
* @length: size of current event
*
* Returns either the length passed in or 0 if full.
* Performs sub-buffer-switch tasks such as invoking callbacks,
* updating padding counts, waking up readers, etc.
*/
size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
{
void *old, *new;
size_t old_subbuf, new_subbuf;
if (unlikely(length > buf->chan->subbuf_size))
goto toobig;
if (buf->offset != buf->chan->subbuf_size + 1) {
buf->prev_padding = buf->chan->subbuf_size - buf->offset;
old_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
buf->padding[old_subbuf] = buf->prev_padding;
buf->subbufs_produced++;
if (waitqueue_active(&buf->read_wait)) {
PREPARE_WORK(&buf->wake_readers, wakeup_readers, buf);
schedule_delayed_work(&buf->wake_readers, 1);
}
}
old = buf->data;
new_subbuf = buf->subbufs_produced % buf->chan->n_subbufs;
new = buf->start + new_subbuf * buf->chan->subbuf_size;
buf->offset = 0;
if (!buf->chan->cb->subbuf_start(buf, new, old, buf->prev_padding)) {
buf->offset = buf->chan->subbuf_size + 1;
return 0;
}
buf->data = new;
buf->padding[new_subbuf] = 0;
if (unlikely(length + buf->offset > buf->chan->subbuf_size))
goto toobig;
return length;
toobig:
buf->chan->last_toobig = length;
return 0;
}
/**
* relay_subbufs_consumed - update the buffer's sub-buffers-consumed count
* @chan: the channel
* @cpu: the cpu associated with the channel buffer to update
* @subbufs_consumed: number of sub-buffers to add to current buf's count
*
* Adds to the channel buffer's consumed sub-buffer count.
* subbufs_consumed should be the number of sub-buffers newly consumed,
* not the total consumed.
*
* NOTE: kernel clients don't need to call this function if the channel
* mode is 'overwrite'.
*/
void relay_subbufs_consumed(struct rchan *chan,
unsigned int cpu,
size_t subbufs_consumed)
{
struct rchan_buf *buf;
if (!chan)
return;
if (cpu >= NR_CPUS || !chan->buf[cpu])
return;
buf = chan->buf[cpu];
buf->subbufs_consumed += subbufs_consumed;
if (buf->subbufs_consumed > buf->subbufs_produced)
buf->subbufs_consumed = buf->subbufs_produced;
}
/**
* relay_destroy_channel - free the channel struct
*
* Should only be called from kref_put().
*/
void relay_destroy_channel(struct kref *kref)
{
struct rchan *chan = container_of(kref, struct rchan, kref);
kfree(chan);
}
/**
* relay_close - close the channel
* @chan: the channel
*
* Closes all channel buffers and frees the channel.
*/
void relay_close(struct rchan *chan)
{
unsigned int i;
if (!chan)
return;
for (i = 0; i < NR_CPUS; i++) {
if (!chan->buf[i])
continue;
relay_close_buf(chan->buf[i]);
}
if (chan->last_toobig)
printk(KERN_WARNING "relayfs: one or more items not logged "
"[item size (%Zd) > sub-buffer size (%Zd)]\n",
chan->last_toobig, chan->subbuf_size);
kref_put(&chan->kref, relay_destroy_channel);
}
/**
* relay_flush - close the channel
* @chan: the channel
*
* Flushes all channel buffers i.e. forces buffer switch.
*/
void relay_flush(struct rchan *chan)
{
unsigned int i;
if (!chan)
return;
for (i = 0; i < NR_CPUS; i++) {
if (!chan->buf[i])
continue;
relay_switch_subbuf(chan->buf[i], 0);
}
}
EXPORT_SYMBOL_GPL(relay_open);
EXPORT_SYMBOL_GPL(relay_close);
EXPORT_SYMBOL_GPL(relay_flush);
EXPORT_SYMBOL_GPL(relay_reset);
EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
EXPORT_SYMBOL_GPL(relay_switch_subbuf);
EXPORT_SYMBOL_GPL(relay_buf_full);