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mac80211: async station powersave handling
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Some devices require that all frames to a station
are flushed when that station goes into powersave
mode before being able to send frames to that
station again when it wakes up or polls -- all in
order to avoid reordering and too many or too few
frames being sent to the station when it polls.

Normally, this is the case unless the station
goes to sleep and wakes up very quickly again.
But in that case, frames for it may be pending
on the hardware queues, and thus races could
happen in the case of multiple hardware queues
used for QoS/WMM. Normally this isn't a problem,
but with the iwlwifi mechanism we need to make
sure the race doesn't happen.

This makes mac80211 able to cope with the race
with driver help by a new WLAN_STA_PS_DRIVER
per-station flag that can be controlled by the
driver and tells mac80211 whether it can transmit
frames or not. This flag must be set according to
very specific rules outlined in the documentation
for the function that controls it.

When we buffer new frames for the station, we
normally set the TIM bit right away, but while
the driver has blocked transmission to that sta
we need to avoid that as well since we cannot
respond to the station if it wakes up due to the
TIM bit. Once the driver unblocks, we can set
the TIM bit.

Similarly, when the station just wakes up, we
need to wait until all other frames are flushed
before we can transmit frames to that station,
so the same applies here, we need to wait for
the driver to give the OK.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Johannes Berg authored and John W. Linville committed Nov 6, 2009
1 parent 70d9f40 commit af81858
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Showing 7 changed files with 200 additions and 85 deletions.
32 changes: 32 additions & 0 deletions include/net/mac80211.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2136,6 +2136,38 @@ struct ieee80211_sta *ieee80211_find_sta(struct ieee80211_vif *vif,
struct ieee80211_sta *ieee80211_find_sta_by_hw(struct ieee80211_hw *hw,
const u8 *addr);

/**
* ieee80211_sta_block_awake - block station from waking up
* @hw: the hardware
* @pubsta: the station
* @block: whether to block or unblock
*
* Some devices require that all frames that are on the queues
* for a specific station that went to sleep are flushed before
* a poll response or frames after the station woke up can be
* delivered to that it. Note that such frames must be rejected
* by the driver as filtered, with the appropriate status flag.
*
* This function allows implementing this mode in a race-free
* manner.
*
* To do this, a driver must keep track of the number of frames
* still enqueued for a specific station. If this number is not
* zero when the station goes to sleep, the driver must call
* this function to force mac80211 to consider the station to
* be asleep regardless of the station's actual state. Once the
* number of outstanding frames reaches zero, the driver must
* call this function again to unblock the station. That will
* cause mac80211 to be able to send ps-poll responses, and if
* the station queried in the meantime then frames will also
* be sent out as a result of this. Additionally, the driver
* will be notified that the station woke up some time after
* it is unblocked, regardless of whether the station actually
* woke up while blocked or not.
*/
void ieee80211_sta_block_awake(struct ieee80211_hw *hw,
struct ieee80211_sta *pubsta, bool block);

/**
* ieee80211_beacon_loss - inform hardware does not receive beacons
*
Expand Down
5 changes: 3 additions & 2 deletions net/mac80211/debugfs_sta.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -66,10 +66,11 @@ static ssize_t sta_flags_read(struct file *file, char __user *userbuf,
char buf[100];
struct sta_info *sta = file->private_data;
u32 staflags = get_sta_flags(sta);
int res = scnprintf(buf, sizeof(buf), "%s%s%s%s%s%s%s%s",
int res = scnprintf(buf, sizeof(buf), "%s%s%s%s%s%s%s%s%s",
staflags & WLAN_STA_AUTH ? "AUTH\n" : "",
staflags & WLAN_STA_ASSOC ? "ASSOC\n" : "",
staflags & WLAN_STA_PS ? "PS\n" : "",
staflags & WLAN_STA_PS_STA ? "PS (sta)\n" : "",
staflags & WLAN_STA_PS_DRIVER ? "PS (driver)\n" : "",
staflags & WLAN_STA_AUTHORIZED ? "AUTHORIZED\n" : "",
staflags & WLAN_STA_SHORT_PREAMBLE ? "SHORT PREAMBLE\n" : "",
staflags & WLAN_STA_WME ? "WME\n" : "",
Expand Down
8 changes: 4 additions & 4 deletions net/mac80211/main.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -385,13 +385,13 @@ static void ieee80211_handle_filtered_frame(struct ieee80211_local *local,
* can be unknown, for example with different interrupt status
* bits.
*/
if (test_sta_flags(sta, WLAN_STA_PS) &&
if (test_sta_flags(sta, WLAN_STA_PS_STA) &&
skb_queue_len(&sta->tx_filtered) < STA_MAX_TX_BUFFER) {
skb_queue_tail(&sta->tx_filtered, skb);
return;
}

if (!test_sta_flags(sta, WLAN_STA_PS) &&
if (!test_sta_flags(sta, WLAN_STA_PS_STA) &&
!(info->flags & IEEE80211_TX_INTFL_RETRIED)) {
/* Software retry the packet once */
info->flags |= IEEE80211_TX_INTFL_RETRIED;
Expand All @@ -406,7 +406,7 @@ static void ieee80211_handle_filtered_frame(struct ieee80211_local *local,
"queue_len=%d PS=%d @%lu\n",
wiphy_name(local->hw.wiphy),
skb_queue_len(&sta->tx_filtered),
!!test_sta_flags(sta, WLAN_STA_PS), jiffies);
!!test_sta_flags(sta, WLAN_STA_PS_STA), jiffies);
#endif
dev_kfree_skb(skb);
}
Expand Down Expand Up @@ -446,7 +446,7 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)

if (sta) {
if (!(info->flags & IEEE80211_TX_STAT_ACK) &&
test_sta_flags(sta, WLAN_STA_PS)) {
test_sta_flags(sta, WLAN_STA_PS_STA)) {
/*
* The STA is in power save mode, so assume
* that this TX packet failed because of that.
Expand Down
86 changes: 15 additions & 71 deletions net/mac80211/rx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -781,7 +781,7 @@ static void ap_sta_ps_start(struct sta_info *sta)
struct ieee80211_local *local = sdata->local;

atomic_inc(&sdata->bss->num_sta_ps);
set_sta_flags(sta, WLAN_STA_PS);
set_sta_flags(sta, WLAN_STA_PS_STA);
drv_sta_notify(local, &sdata->vif, STA_NOTIFY_SLEEP, &sta->sta);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
printk(KERN_DEBUG "%s: STA %pM aid %d enters power save mode\n",
Expand All @@ -792,33 +792,25 @@ static void ap_sta_ps_start(struct sta_info *sta)
static void ap_sta_ps_end(struct sta_info *sta)
{
struct ieee80211_sub_if_data *sdata = sta->sdata;
struct ieee80211_local *local = sdata->local;
int sent, buffered;

atomic_dec(&sdata->bss->num_sta_ps);

clear_sta_flags(sta, WLAN_STA_PS);
drv_sta_notify(local, &sdata->vif, STA_NOTIFY_AWAKE, &sta->sta);

if (!skb_queue_empty(&sta->ps_tx_buf))
sta_info_clear_tim_bit(sta);
clear_sta_flags(sta, WLAN_STA_PS_STA);

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
printk(KERN_DEBUG "%s: STA %pM aid %d exits power save mode\n",
sdata->dev->name, sta->sta.addr, sta->sta.aid);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */

/* Send all buffered frames to the station */
sent = ieee80211_add_pending_skbs(local, &sta->tx_filtered);
buffered = ieee80211_add_pending_skbs(local, &sta->ps_tx_buf);
sent += buffered;
local->total_ps_buffered -= buffered;

if (test_sta_flags(sta, WLAN_STA_PS_DRIVER)) {
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
printk(KERN_DEBUG "%s: STA %pM aid %d sending %d filtered/%d PS frames "
"since STA not sleeping anymore\n", sdata->dev->name,
sta->sta.addr, sta->sta.aid, sent - buffered, buffered);
printk(KERN_DEBUG "%s: STA %pM aid %d driver-ps-blocked\n",
sdata->dev->name, sta->sta.addr, sta->sta.aid);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
return;
}

ieee80211_sta_ps_deliver_wakeup(sta);
}

static ieee80211_rx_result debug_noinline
Expand Down Expand Up @@ -866,7 +858,7 @@ ieee80211_rx_h_sta_process(struct ieee80211_rx_data *rx)
if (!ieee80211_has_morefrags(hdr->frame_control) &&
(rx->sdata->vif.type == NL80211_IFTYPE_AP ||
rx->sdata->vif.type == NL80211_IFTYPE_AP_VLAN)) {
if (test_sta_flags(sta, WLAN_STA_PS)) {
if (test_sta_flags(sta, WLAN_STA_PS_STA)) {
/*
* Ignore doze->wake transitions that are
* indicated by non-data frames, the standard
Expand Down Expand Up @@ -1094,9 +1086,7 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
static ieee80211_rx_result debug_noinline
ieee80211_rx_h_ps_poll(struct ieee80211_rx_data *rx)
{
struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(rx->dev);
struct sk_buff *skb;
int no_pending_pkts;
struct ieee80211_sub_if_data *sdata = rx->sdata;
__le16 fc = ((struct ieee80211_hdr *)rx->skb->data)->frame_control;

if (likely(!rx->sta || !ieee80211_is_pspoll(fc) ||
Expand All @@ -1107,56 +1097,10 @@ ieee80211_rx_h_ps_poll(struct ieee80211_rx_data *rx)
(sdata->vif.type != NL80211_IFTYPE_AP_VLAN))
return RX_DROP_UNUSABLE;

skb = skb_dequeue(&rx->sta->tx_filtered);
if (!skb) {
skb = skb_dequeue(&rx->sta->ps_tx_buf);
if (skb)
rx->local->total_ps_buffered--;
}
no_pending_pkts = skb_queue_empty(&rx->sta->tx_filtered) &&
skb_queue_empty(&rx->sta->ps_tx_buf);

if (skb) {
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct ieee80211_hdr *hdr =
(struct ieee80211_hdr *) skb->data;

/*
* Tell TX path to send this frame even though the STA may
* still remain is PS mode after this frame exchange.
*/
info->flags |= IEEE80211_TX_CTL_PSPOLL_RESPONSE;

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
printk(KERN_DEBUG "STA %pM aid %d: PS Poll (entries after %d)\n",
rx->sta->sta.addr, rx->sta->sta.aid,
skb_queue_len(&rx->sta->ps_tx_buf));
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */

/* Use MoreData flag to indicate whether there are more
* buffered frames for this STA */
if (no_pending_pkts)
hdr->frame_control &= cpu_to_le16(~IEEE80211_FCTL_MOREDATA);
else
hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREDATA);

ieee80211_add_pending_skb(rx->local, skb);

if (no_pending_pkts)
sta_info_clear_tim_bit(rx->sta);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
} else {
/*
* FIXME: This can be the result of a race condition between
* us expiring a frame and the station polling for it.
* Should we send it a null-func frame indicating we
* have nothing buffered for it?
*/
printk(KERN_DEBUG "%s: STA %pM sent PS Poll even "
"though there are no buffered frames for it\n",
rx->dev->name, rx->sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
}
if (!test_sta_flags(rx->sta, WLAN_STA_PS_DRIVER))
ieee80211_sta_ps_deliver_poll_response(rx->sta);
else
set_sta_flags(rx->sta, WLAN_STA_PSPOLL);

/* Free PS Poll skb here instead of returning RX_DROP that would
* count as an dropped frame. */
Expand Down
118 changes: 117 additions & 1 deletion net/mac80211/sta_info.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -171,6 +171,8 @@ void sta_info_destroy(struct sta_info *sta)

local = sta->local;

cancel_work_sync(&sta->drv_unblock_wk);

rate_control_remove_sta_debugfs(sta);
ieee80211_sta_debugfs_remove(sta);

Expand Down Expand Up @@ -259,6 +261,21 @@ static void sta_info_hash_add(struct ieee80211_local *local,
rcu_assign_pointer(local->sta_hash[STA_HASH(sta->sta.addr)], sta);
}

static void sta_unblock(struct work_struct *wk)
{
struct sta_info *sta;

sta = container_of(wk, struct sta_info, drv_unblock_wk);

if (sta->dead)
return;

if (!test_sta_flags(sta, WLAN_STA_PS_STA))
ieee80211_sta_ps_deliver_wakeup(sta);
else if (test_and_clear_sta_flags(sta, WLAN_STA_PSPOLL))
ieee80211_sta_ps_deliver_poll_response(sta);
}

struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
u8 *addr, gfp_t gfp)
{
Expand All @@ -272,6 +289,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,

spin_lock_init(&sta->lock);
spin_lock_init(&sta->flaglock);
INIT_WORK(&sta->drv_unblock_wk, sta_unblock);

memcpy(sta->sta.addr, addr, ETH_ALEN);
sta->local = local;
Expand Down Expand Up @@ -478,8 +496,10 @@ static void __sta_info_unlink(struct sta_info **sta)
}

list_del(&(*sta)->list);
(*sta)->dead = true;

if (test_and_clear_sta_flags(*sta, WLAN_STA_PS)) {
if (test_and_clear_sta_flags(*sta,
WLAN_STA_PS_STA | WLAN_STA_PS_DRIVER)) {
BUG_ON(!sdata->bss);

atomic_dec(&sdata->bss->num_sta_ps);
Expand Down Expand Up @@ -825,3 +845,99 @@ struct ieee80211_sta *ieee80211_find_sta(struct ieee80211_vif *vif,
return ieee80211_find_sta_by_hw(&sdata->local->hw, addr);
}
EXPORT_SYMBOL(ieee80211_find_sta);

/* powersave support code */
void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta)
{
struct ieee80211_sub_if_data *sdata = sta->sdata;
struct ieee80211_local *local = sdata->local;
int sent, buffered;

drv_sta_notify(local, &sdata->vif, STA_NOTIFY_AWAKE, &sta->sta);

if (!skb_queue_empty(&sta->ps_tx_buf))
sta_info_clear_tim_bit(sta);

/* Send all buffered frames to the station */
sent = ieee80211_add_pending_skbs(local, &sta->tx_filtered);
buffered = ieee80211_add_pending_skbs(local, &sta->ps_tx_buf);
sent += buffered;
local->total_ps_buffered -= buffered;

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
printk(KERN_DEBUG "%s: STA %pM aid %d sending %d filtered/%d PS frames "
"since STA not sleeping anymore\n", sdata->dev->name,
sta->sta.addr, sta->sta.aid, sent - buffered, buffered);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
}

void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta)
{
struct ieee80211_sub_if_data *sdata = sta->sdata;
struct ieee80211_local *local = sdata->local;
struct sk_buff *skb;
int no_pending_pkts;

skb = skb_dequeue(&sta->tx_filtered);
if (!skb) {
skb = skb_dequeue(&sta->ps_tx_buf);
if (skb)
local->total_ps_buffered--;
}
no_pending_pkts = skb_queue_empty(&sta->tx_filtered) &&
skb_queue_empty(&sta->ps_tx_buf);

if (skb) {
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct ieee80211_hdr *hdr =
(struct ieee80211_hdr *) skb->data;

/*
* Tell TX path to send this frame even though the STA may
* still remain is PS mode after this frame exchange.
*/
info->flags |= IEEE80211_TX_CTL_PSPOLL_RESPONSE;

#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
printk(KERN_DEBUG "STA %pM aid %d: PS Poll (entries after %d)\n",
sta->sta.addr, sta->sta.aid,
skb_queue_len(&sta->ps_tx_buf));
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */

/* Use MoreData flag to indicate whether there are more
* buffered frames for this STA */
if (no_pending_pkts)
hdr->frame_control &= cpu_to_le16(~IEEE80211_FCTL_MOREDATA);
else
hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_MOREDATA);

ieee80211_add_pending_skb(local, skb);

if (no_pending_pkts)
sta_info_clear_tim_bit(sta);
#ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
} else {
/*
* FIXME: This can be the result of a race condition between
* us expiring a frame and the station polling for it.
* Should we send it a null-func frame indicating we
* have nothing buffered for it?
*/
printk(KERN_DEBUG "%s: STA %pM sent PS Poll even "
"though there are no buffered frames for it\n",
sdata->dev->name, sta->sta.addr);
#endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
}
}

void ieee80211_sta_block_awake(struct ieee80211_hw *hw,
struct ieee80211_sta *pubsta, bool block)
{
struct sta_info *sta = container_of(pubsta, struct sta_info, sta);

if (block)
set_sta_flags(sta, WLAN_STA_PS_DRIVER);
else
ieee80211_queue_work(hw, &sta->drv_unblock_wk);
}
EXPORT_SYMBOL(ieee80211_sta_block_awake);
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