linux/net/mac80211/rc80211_pid_algo.c
Johannes Berg d0709a6518 mac80211: RCU-ify STA info structure access
This makes access to the STA hash table/list use RCU to protect
against freeing of items. However, it's not a true RCU, the
copy step is missing: whenever somebody changes a STA item it
is simply updated. This is an existing race condition that is
now somewhat understandable.

This patch also fixes the race key freeing vs. STA destruction
by making sure that sta_info_destroy() is always called under
RTNL and frees the key.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2008-03-06 15:30:46 -05:00

561 lines
17 KiB
C

/*
* Copyright 2002-2005, Instant802 Networks, Inc.
* Copyright 2005, Devicescape Software, Inc.
* Copyright 2007, Mattias Nissler <mattias.nissler@gmx.de>
* Copyright 2007-2008, Stefano Brivio <stefano.brivio@polimi.it>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/netdevice.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/debugfs.h>
#include <net/mac80211.h>
#include "ieee80211_rate.h"
#include "mesh.h"
#include "rc80211_pid.h"
/* This is an implementation of a TX rate control algorithm that uses a PID
* controller. Given a target failed frames rate, the controller decides about
* TX rate changes to meet the target failed frames rate.
*
* The controller basically computes the following:
*
* adj = CP * err + CI * err_avg + CD * (err - last_err) * (1 + sharpening)
*
* where
* adj adjustment value that is used to switch TX rate (see below)
* err current error: target vs. current failed frames percentage
* last_err last error
* err_avg average (i.e. poor man's integral) of recent errors
* sharpening non-zero when fast response is needed (i.e. right after
* association or no frames sent for a long time), heading
* to zero over time
* CP Proportional coefficient
* CI Integral coefficient
* CD Derivative coefficient
*
* CP, CI, CD are subject to careful tuning.
*
* The integral component uses a exponential moving average approach instead of
* an actual sliding window. The advantage is that we don't need to keep an
* array of the last N error values and computation is easier.
*
* Once we have the adj value, we map it to a rate by means of a learning
* algorithm. This algorithm keeps the state of the percentual failed frames
* difference between rates. The behaviour of the lowest available rate is kept
* as a reference value, and every time we switch between two rates, we compute
* the difference between the failed frames each rate exhibited. By doing so,
* we compare behaviours which different rates exhibited in adjacent timeslices,
* thus the comparison is minimally affected by external conditions. This
* difference gets propagated to the whole set of measurements, so that the
* reference is always the same. Periodically, we normalize this set so that
* recent events weigh the most. By comparing the adj value with this set, we
* avoid pejorative switches to lower rates and allow for switches to higher
* rates if they behaved well.
*
* Note that for the computations we use a fixed-point representation to avoid
* floating point arithmetic. Hence, all values are shifted left by
* RC_PID_ARITH_SHIFT.
*/
/* Adjust the rate while ensuring that we won't switch to a lower rate if it
* exhibited a worse failed frames behaviour and we'll choose the highest rate
* whose failed frames behaviour is not worse than the one of the original rate
* target. While at it, check that the new rate is valid. */
static void rate_control_pid_adjust_rate(struct ieee80211_local *local,
struct sta_info *sta, int adj,
struct rc_pid_rateinfo *rinfo)
{
struct ieee80211_sub_if_data *sdata;
struct ieee80211_supported_band *sband;
int cur_sorted, new_sorted, probe, tmp, n_bitrates, band;
int cur = sta->txrate_idx;
sdata = sta->sdata;
sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
band = sband->band;
n_bitrates = sband->n_bitrates;
/* Map passed arguments to sorted values. */
cur_sorted = rinfo[cur].rev_index;
new_sorted = cur_sorted + adj;
/* Check limits. */
if (new_sorted < 0)
new_sorted = rinfo[0].rev_index;
else if (new_sorted >= n_bitrates)
new_sorted = rinfo[n_bitrates - 1].rev_index;
tmp = new_sorted;
if (adj < 0) {
/* Ensure that the rate decrease isn't disadvantageous. */
for (probe = cur_sorted; probe >= new_sorted; probe--)
if (rinfo[probe].diff <= rinfo[cur_sorted].diff &&
rate_supported(sta, band, rinfo[probe].index))
tmp = probe;
} else {
/* Look for rate increase with zero (or below) cost. */
for (probe = new_sorted + 1; probe < n_bitrates; probe++)
if (rinfo[probe].diff <= rinfo[new_sorted].diff &&
rate_supported(sta, band, rinfo[probe].index))
tmp = probe;
}
/* Fit the rate found to the nearest supported rate. */
do {
if (rate_supported(sta, band, rinfo[tmp].index)) {
sta->txrate_idx = rinfo[tmp].index;
break;
}
if (adj < 0)
tmp--;
else
tmp++;
} while (tmp < n_bitrates && tmp >= 0);
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_rate_change(
&((struct rc_pid_sta_info *)sta->rate_ctrl_priv)->events,
sta->txrate_idx, sband->bitrates[sta->txrate_idx].bitrate);
#endif
}
/* Normalize the failed frames per-rate differences. */
static void rate_control_pid_normalize(struct rc_pid_info *pinfo, int l)
{
int i, norm_offset = pinfo->norm_offset;
struct rc_pid_rateinfo *r = pinfo->rinfo;
if (r[0].diff > norm_offset)
r[0].diff -= norm_offset;
else if (r[0].diff < -norm_offset)
r[0].diff += norm_offset;
for (i = 0; i < l - 1; i++)
if (r[i + 1].diff > r[i].diff + norm_offset)
r[i + 1].diff -= norm_offset;
else if (r[i + 1].diff <= r[i].diff)
r[i + 1].diff += norm_offset;
}
static void rate_control_pid_sample(struct rc_pid_info *pinfo,
struct ieee80211_local *local,
struct sta_info *sta)
{
#ifdef CONFIG_MAC80211_MESH
struct ieee80211_sub_if_data *sdata = sta->sdata;
#endif
struct rc_pid_sta_info *spinfo = sta->rate_ctrl_priv;
struct rc_pid_rateinfo *rinfo = pinfo->rinfo;
struct ieee80211_supported_band *sband;
u32 pf;
s32 err_avg;
u32 err_prop;
u32 err_int;
u32 err_der;
int adj, i, j, tmp;
unsigned long period;
sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
spinfo = sta->rate_ctrl_priv;
/* In case nothing happened during the previous control interval, turn
* the sharpening factor on. */
period = (HZ * pinfo->sampling_period + 500) / 1000;
if (!period)
period = 1;
if (jiffies - spinfo->last_sample > 2 * period)
spinfo->sharp_cnt = pinfo->sharpen_duration;
spinfo->last_sample = jiffies;
/* This should never happen, but in case, we assume the old sample is
* still a good measurement and copy it. */
if (unlikely(spinfo->tx_num_xmit == 0))
pf = spinfo->last_pf;
else {
pf = spinfo->tx_num_failed * 100 / spinfo->tx_num_xmit;
#ifdef CONFIG_MAC80211_MESH
if (pf == 100 &&
sdata->vif.type == IEEE80211_IF_TYPE_MESH_POINT)
mesh_plink_broken(sta);
#endif
pf <<= RC_PID_ARITH_SHIFT;
sta->fail_avg = ((pf + (spinfo->last_pf << 3)) / 9)
>> RC_PID_ARITH_SHIFT;
}
spinfo->tx_num_xmit = 0;
spinfo->tx_num_failed = 0;
/* If we just switched rate, update the rate behaviour info. */
if (pinfo->oldrate != sta->txrate_idx) {
i = rinfo[pinfo->oldrate].rev_index;
j = rinfo[sta->txrate_idx].rev_index;
tmp = (pf - spinfo->last_pf);
tmp = RC_PID_DO_ARITH_RIGHT_SHIFT(tmp, RC_PID_ARITH_SHIFT);
rinfo[j].diff = rinfo[i].diff + tmp;
pinfo->oldrate = sta->txrate_idx;
}
rate_control_pid_normalize(pinfo, sband->n_bitrates);
/* Compute the proportional, integral and derivative errors. */
err_prop = (pinfo->target << RC_PID_ARITH_SHIFT) - pf;
err_avg = spinfo->err_avg_sc >> pinfo->smoothing_shift;
spinfo->err_avg_sc = spinfo->err_avg_sc - err_avg + err_prop;
err_int = spinfo->err_avg_sc >> pinfo->smoothing_shift;
err_der = (pf - spinfo->last_pf) *
(1 + pinfo->sharpen_factor * spinfo->sharp_cnt);
spinfo->last_pf = pf;
if (spinfo->sharp_cnt)
spinfo->sharp_cnt--;
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_pf_sample(&spinfo->events, pf, err_prop, err_int,
err_der);
#endif
/* Compute the controller output. */
adj = (err_prop * pinfo->coeff_p + err_int * pinfo->coeff_i
+ err_der * pinfo->coeff_d);
adj = RC_PID_DO_ARITH_RIGHT_SHIFT(adj, 2 * RC_PID_ARITH_SHIFT);
/* Change rate. */
if (adj)
rate_control_pid_adjust_rate(local, sta, adj, rinfo);
}
static void rate_control_pid_tx_status(void *priv, struct net_device *dev,
struct sk_buff *skb,
struct ieee80211_tx_status *status)
{
struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
struct ieee80211_sub_if_data *sdata;
struct rc_pid_info *pinfo = priv;
struct sta_info *sta;
struct rc_pid_sta_info *spinfo;
unsigned long period;
struct ieee80211_supported_band *sband;
rcu_read_lock();
sta = sta_info_get(local, hdr->addr1);
sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
if (!sta)
goto unlock;
/* Don't update the state if we're not controlling the rate. */
sdata = sta->sdata;
if (sdata->bss && sdata->bss->force_unicast_rateidx > -1) {
sta->txrate_idx = sdata->bss->max_ratectrl_rateidx;
goto unlock;
}
/* Ignore all frames that were sent with a different rate than the rate
* we currently advise mac80211 to use. */
if (status->control.tx_rate != &sband->bitrates[sta->txrate_idx])
goto unlock;
spinfo = sta->rate_ctrl_priv;
spinfo->tx_num_xmit++;
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_tx_status(&spinfo->events, status);
#endif
/* We count frames that totally failed to be transmitted as two bad
* frames, those that made it out but had some retries as one good and
* one bad frame. */
if (status->excessive_retries) {
spinfo->tx_num_failed += 2;
spinfo->tx_num_xmit++;
} else if (status->retry_count) {
spinfo->tx_num_failed++;
spinfo->tx_num_xmit++;
}
if (status->excessive_retries) {
sta->tx_retry_failed++;
sta->tx_num_consecutive_failures++;
sta->tx_num_mpdu_fail++;
} else {
sta->tx_num_consecutive_failures = 0;
sta->tx_num_mpdu_ok++;
}
sta->tx_retry_count += status->retry_count;
sta->tx_num_mpdu_fail += status->retry_count;
/* Update PID controller state. */
period = (HZ * pinfo->sampling_period + 500) / 1000;
if (!period)
period = 1;
if (time_after(jiffies, spinfo->last_sample + period))
rate_control_pid_sample(pinfo, local, sta);
unlock:
rcu_read_unlock();
}
static void rate_control_pid_get_rate(void *priv, struct net_device *dev,
struct ieee80211_supported_band *sband,
struct sk_buff *skb,
struct rate_selection *sel)
{
struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
struct ieee80211_sub_if_data *sdata;
struct sta_info *sta;
int rateidx;
u16 fc;
rcu_read_lock();
sta = sta_info_get(local, hdr->addr1);
/* Send management frames and broadcast/multicast data using lowest
* rate. */
fc = le16_to_cpu(hdr->frame_control);
if ((fc & IEEE80211_FCTL_FTYPE) != IEEE80211_FTYPE_DATA ||
is_multicast_ether_addr(hdr->addr1) || !sta) {
sel->rate = rate_lowest(local, sband, sta);
rcu_read_unlock();
return;
}
/* If a forced rate is in effect, select it. */
sdata = IEEE80211_DEV_TO_SUB_IF(dev);
if (sdata->bss && sdata->bss->force_unicast_rateidx > -1)
sta->txrate_idx = sdata->bss->force_unicast_rateidx;
rateidx = sta->txrate_idx;
if (rateidx >= sband->n_bitrates)
rateidx = sband->n_bitrates - 1;
sta->last_txrate_idx = rateidx;
rcu_read_unlock();
sel->rate = &sband->bitrates[rateidx];
#ifdef CONFIG_MAC80211_DEBUGFS
rate_control_pid_event_tx_rate(
&((struct rc_pid_sta_info *) sta->rate_ctrl_priv)->events,
rateidx, sband->bitrates[rateidx].bitrate);
#endif
}
static void rate_control_pid_rate_init(void *priv, void *priv_sta,
struct ieee80211_local *local,
struct sta_info *sta)
{
/* TODO: This routine should consider using RSSI from previous packets
* as we need to have IEEE 802.1X auth succeed immediately after assoc..
* Until that method is implemented, we will use the lowest supported
* rate as a workaround. */
struct ieee80211_supported_band *sband;
sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
sta->txrate_idx = rate_lowest_index(local, sband, sta);
sta->fail_avg = 0;
}
static void *rate_control_pid_alloc(struct ieee80211_local *local)
{
struct rc_pid_info *pinfo;
struct rc_pid_rateinfo *rinfo;
struct ieee80211_supported_band *sband;
int i, j, tmp;
bool s;
#ifdef CONFIG_MAC80211_DEBUGFS
struct rc_pid_debugfs_entries *de;
#endif
sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
if (!pinfo)
return NULL;
/* We can safely assume that sband won't change unless we get
* reinitialized. */
rinfo = kmalloc(sizeof(*rinfo) * sband->n_bitrates, GFP_ATOMIC);
if (!rinfo) {
kfree(pinfo);
return NULL;
}
/* Sort the rates. This is optimized for the most common case (i.e.
* almost-sorted CCK+OFDM rates). Kind of bubble-sort with reversed
* mapping too. */
for (i = 0; i < sband->n_bitrates; i++) {
rinfo[i].index = i;
rinfo[i].rev_index = i;
if (pinfo->fast_start)
rinfo[i].diff = 0;
else
rinfo[i].diff = i * pinfo->norm_offset;
}
for (i = 1; i < sband->n_bitrates; i++) {
s = 0;
for (j = 0; j < sband->n_bitrates - i; j++)
if (unlikely(sband->bitrates[rinfo[j].index].bitrate >
sband->bitrates[rinfo[j + 1].index].bitrate)) {
tmp = rinfo[j].index;
rinfo[j].index = rinfo[j + 1].index;
rinfo[j + 1].index = tmp;
rinfo[rinfo[j].index].rev_index = j;
rinfo[rinfo[j + 1].index].rev_index = j + 1;
s = 1;
}
if (!s)
break;
}
pinfo->target = RC_PID_TARGET_PF;
pinfo->sampling_period = RC_PID_INTERVAL;
pinfo->coeff_p = RC_PID_COEFF_P;
pinfo->coeff_i = RC_PID_COEFF_I;
pinfo->coeff_d = RC_PID_COEFF_D;
pinfo->smoothing_shift = RC_PID_SMOOTHING_SHIFT;
pinfo->sharpen_factor = RC_PID_SHARPENING_FACTOR;
pinfo->sharpen_duration = RC_PID_SHARPENING_DURATION;
pinfo->norm_offset = RC_PID_NORM_OFFSET;
pinfo->fast_start = RC_PID_FAST_START;
pinfo->rinfo = rinfo;
pinfo->oldrate = 0;
#ifdef CONFIG_MAC80211_DEBUGFS
de = &pinfo->dentries;
de->dir = debugfs_create_dir("rc80211_pid",
local->hw.wiphy->debugfsdir);
de->target = debugfs_create_u32("target_pf", S_IRUSR | S_IWUSR,
de->dir, &pinfo->target);
de->sampling_period = debugfs_create_u32("sampling_period",
S_IRUSR | S_IWUSR, de->dir,
&pinfo->sampling_period);
de->coeff_p = debugfs_create_u32("coeff_p", S_IRUSR | S_IWUSR,
de->dir, &pinfo->coeff_p);
de->coeff_i = debugfs_create_u32("coeff_i", S_IRUSR | S_IWUSR,
de->dir, &pinfo->coeff_i);
de->coeff_d = debugfs_create_u32("coeff_d", S_IRUSR | S_IWUSR,
de->dir, &pinfo->coeff_d);
de->smoothing_shift = debugfs_create_u32("smoothing_shift",
S_IRUSR | S_IWUSR, de->dir,
&pinfo->smoothing_shift);
de->sharpen_factor = debugfs_create_u32("sharpen_factor",
S_IRUSR | S_IWUSR, de->dir,
&pinfo->sharpen_factor);
de->sharpen_duration = debugfs_create_u32("sharpen_duration",
S_IRUSR | S_IWUSR, de->dir,
&pinfo->sharpen_duration);
de->norm_offset = debugfs_create_u32("norm_offset",
S_IRUSR | S_IWUSR, de->dir,
&pinfo->norm_offset);
de->fast_start = debugfs_create_bool("fast_start",
S_IRUSR | S_IWUSR, de->dir,
&pinfo->fast_start);
#endif
return pinfo;
}
static void rate_control_pid_free(void *priv)
{
struct rc_pid_info *pinfo = priv;
#ifdef CONFIG_MAC80211_DEBUGFS
struct rc_pid_debugfs_entries *de = &pinfo->dentries;
debugfs_remove(de->fast_start);
debugfs_remove(de->norm_offset);
debugfs_remove(de->sharpen_duration);
debugfs_remove(de->sharpen_factor);
debugfs_remove(de->smoothing_shift);
debugfs_remove(de->coeff_d);
debugfs_remove(de->coeff_i);
debugfs_remove(de->coeff_p);
debugfs_remove(de->sampling_period);
debugfs_remove(de->target);
debugfs_remove(de->dir);
#endif
kfree(pinfo->rinfo);
kfree(pinfo);
}
static void rate_control_pid_clear(void *priv)
{
}
static void *rate_control_pid_alloc_sta(void *priv, gfp_t gfp)
{
struct rc_pid_sta_info *spinfo;
spinfo = kzalloc(sizeof(*spinfo), gfp);
if (spinfo == NULL)
return NULL;
spinfo->last_sample = jiffies;
#ifdef CONFIG_MAC80211_DEBUGFS
spin_lock_init(&spinfo->events.lock);
init_waitqueue_head(&spinfo->events.waitqueue);
#endif
return spinfo;
}
static void rate_control_pid_free_sta(void *priv, void *priv_sta)
{
struct rc_pid_sta_info *spinfo = priv_sta;
kfree(spinfo);
}
static struct rate_control_ops mac80211_rcpid = {
.name = "pid",
.tx_status = rate_control_pid_tx_status,
.get_rate = rate_control_pid_get_rate,
.rate_init = rate_control_pid_rate_init,
.clear = rate_control_pid_clear,
.alloc = rate_control_pid_alloc,
.free = rate_control_pid_free,
.alloc_sta = rate_control_pid_alloc_sta,
.free_sta = rate_control_pid_free_sta,
#ifdef CONFIG_MAC80211_DEBUGFS
.add_sta_debugfs = rate_control_pid_add_sta_debugfs,
.remove_sta_debugfs = rate_control_pid_remove_sta_debugfs,
#endif
};
MODULE_DESCRIPTION("PID controller based rate control algorithm");
MODULE_AUTHOR("Stefano Brivio");
MODULE_AUTHOR("Mattias Nissler");
MODULE_LICENSE("GPL");
int __init rc80211_pid_init(void)
{
return ieee80211_rate_control_register(&mac80211_rcpid);
}
void rc80211_pid_exit(void)
{
ieee80211_rate_control_unregister(&mac80211_rcpid);
}
#ifdef CONFIG_MAC80211_RC_PID_MODULE
module_init(rc80211_pid_init);
module_exit(rc80211_pid_exit);
#endif