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mac80211: serialize rx path workers
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This patch addresses the issue of serialization between
the main rx path and various reorder release timers.

<http://www.spinics.net/lists/linux-wireless/msg57214.html>

It converts the previously local "frames" queue into
a global rx queue [rx_skb_queue]. This way, everyone
(be it the main rx-path or some reorder release timeout)
can add frames to it.

Only one active rx handler worker [ieee80211_rx_handlers]
is needed. All other threads which have lost the race of
"runnning_rx_handler" can now simply "return", knowing that
the thread who had the "edge" will also take care of their
workload.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Christian Lamparter authored and John W. Linville committed Jan 4, 2011
1 parent 1186488 commit 24a8fda
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Showing 3 changed files with 49 additions and 43 deletions.
9 changes: 9 additions & 0 deletions net/mac80211/ieee80211_i.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -761,6 +761,15 @@ struct ieee80211_local {
struct sk_buff_head skb_queue;
struct sk_buff_head skb_queue_unreliable;

/*
* Internal FIFO queue which is shared between multiple rx path
* stages. Its main task is to provide a serialization mechanism,
* so all rx handlers can enjoy having exclusive access to their
* private data structures.
*/
struct sk_buff_head rx_skb_queue;
bool running_rx_handler; /* protected by rx_skb_queue.lock */

/* Station data */
/*
* The mutex only protects the list and counter,
Expand Down
3 changes: 3 additions & 0 deletions net/mac80211/main.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -569,6 +569,8 @@ struct ieee80211_hw *ieee80211_alloc_hw(size_t priv_data_len,
spin_lock_init(&local->filter_lock);
spin_lock_init(&local->queue_stop_reason_lock);

skb_queue_head_init(&local->rx_skb_queue);

INIT_DELAYED_WORK(&local->scan_work, ieee80211_scan_work);

ieee80211_work_init(local);
Expand Down Expand Up @@ -912,6 +914,7 @@ void ieee80211_unregister_hw(struct ieee80211_hw *hw)
wiphy_warn(local->hw.wiphy, "skb_queue not empty\n");
skb_queue_purge(&local->skb_queue);
skb_queue_purge(&local->skb_queue_unreliable);
skb_queue_purge(&local->rx_skb_queue);

destroy_workqueue(local->workqueue);
wiphy_unregister(local->hw.wiphy);
Expand Down
80 changes: 37 additions & 43 deletions net/mac80211/rx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -533,9 +533,9 @@ static inline u16 seq_sub(u16 sq1, u16 sq2)

static void ieee80211_release_reorder_frame(struct ieee80211_hw *hw,
struct tid_ampdu_rx *tid_agg_rx,
int index,
struct sk_buff_head *frames)
int index)
{
struct ieee80211_local *local = hw_to_local(hw);
struct sk_buff *skb = tid_agg_rx->reorder_buf[index];
struct ieee80211_rx_status *status;

Expand All @@ -549,16 +549,15 @@ static void ieee80211_release_reorder_frame(struct ieee80211_hw *hw,
tid_agg_rx->reorder_buf[index] = NULL;
status = IEEE80211_SKB_RXCB(skb);
status->rx_flags |= IEEE80211_RX_DEFERRED_RELEASE;
__skb_queue_tail(frames, skb);
skb_queue_tail(&local->rx_skb_queue, skb);

no_frame:
tid_agg_rx->head_seq_num = seq_inc(tid_agg_rx->head_seq_num);
}

static void ieee80211_release_reorder_frames(struct ieee80211_hw *hw,
struct tid_ampdu_rx *tid_agg_rx,
u16 head_seq_num,
struct sk_buff_head *frames)
u16 head_seq_num)
{
int index;

Expand All @@ -567,7 +566,7 @@ static void ieee80211_release_reorder_frames(struct ieee80211_hw *hw,
while (seq_less(tid_agg_rx->head_seq_num, head_seq_num)) {
index = seq_sub(tid_agg_rx->head_seq_num, tid_agg_rx->ssn) %
tid_agg_rx->buf_size;
ieee80211_release_reorder_frame(hw, tid_agg_rx, index, frames);
ieee80211_release_reorder_frame(hw, tid_agg_rx, index);
}
}

Expand All @@ -583,8 +582,7 @@ static void ieee80211_release_reorder_frames(struct ieee80211_hw *hw,
#define HT_RX_REORDER_BUF_TIMEOUT (HZ / 10)

static void ieee80211_sta_reorder_release(struct ieee80211_hw *hw,
struct tid_ampdu_rx *tid_agg_rx,
struct sk_buff_head *frames)
struct tid_ampdu_rx *tid_agg_rx)
{
int index, j;

Expand Down Expand Up @@ -615,8 +613,7 @@ static void ieee80211_sta_reorder_release(struct ieee80211_hw *hw,
wiphy_debug(hw->wiphy,
"release an RX reorder frame due to timeout on earlier frames\n");
#endif
ieee80211_release_reorder_frame(hw, tid_agg_rx,
j, frames);
ieee80211_release_reorder_frame(hw, tid_agg_rx, j);

/*
* Increment the head seq# also for the skipped slots.
Expand All @@ -626,7 +623,7 @@ static void ieee80211_sta_reorder_release(struct ieee80211_hw *hw,
skipped = 0;
}
} else while (tid_agg_rx->reorder_buf[index]) {
ieee80211_release_reorder_frame(hw, tid_agg_rx, index, frames);
ieee80211_release_reorder_frame(hw, tid_agg_rx, index);
index = seq_sub(tid_agg_rx->head_seq_num, tid_agg_rx->ssn) %
tid_agg_rx->buf_size;
}
Expand Down Expand Up @@ -682,8 +679,7 @@ static void ieee80211_sta_reorder_release(struct ieee80211_hw *hw,
*/
static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
struct tid_ampdu_rx *tid_agg_rx,
struct sk_buff *skb,
struct sk_buff_head *frames)
struct sk_buff *skb)
{
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
u16 sc = le16_to_cpu(hdr->seq_ctrl);
Expand All @@ -710,8 +706,7 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
if (!seq_less(mpdu_seq_num, head_seq_num + buf_size)) {
head_seq_num = seq_inc(seq_sub(mpdu_seq_num, buf_size));
/* release stored frames up to new head to stack */
ieee80211_release_reorder_frames(hw, tid_agg_rx, head_seq_num,
frames);
ieee80211_release_reorder_frames(hw, tid_agg_rx, head_seq_num);
}

/* Now the new frame is always in the range of the reordering buffer */
Expand Down Expand Up @@ -739,7 +734,7 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
tid_agg_rx->reorder_buf[index] = skb;
tid_agg_rx->reorder_time[index] = jiffies;
tid_agg_rx->stored_mpdu_num++;
ieee80211_sta_reorder_release(hw, tid_agg_rx, frames);
ieee80211_sta_reorder_release(hw, tid_agg_rx);

out:
spin_unlock(&tid_agg_rx->reorder_lock);
Expand All @@ -750,8 +745,7 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
* Reorder MPDUs from A-MPDUs, keeping them on a buffer. Returns
* true if the MPDU was buffered, false if it should be processed.
*/
static void ieee80211_rx_reorder_ampdu(struct ieee80211_rx_data *rx,
struct sk_buff_head *frames)
static void ieee80211_rx_reorder_ampdu(struct ieee80211_rx_data *rx)
{
struct sk_buff *skb = rx->skb;
struct ieee80211_local *local = rx->local;
Expand Down Expand Up @@ -806,11 +800,11 @@ static void ieee80211_rx_reorder_ampdu(struct ieee80211_rx_data *rx,
* sure that we cannot get to it any more before doing
* anything with it.
*/
if (ieee80211_sta_manage_reorder_buf(hw, tid_agg_rx, skb, frames))
if (ieee80211_sta_manage_reorder_buf(hw, tid_agg_rx, skb))
return;

dont_reorder:
__skb_queue_tail(frames, skb);
skb_queue_tail(&local->rx_skb_queue, skb);
}

static ieee80211_rx_result debug_noinline
Expand Down Expand Up @@ -1931,7 +1925,7 @@ ieee80211_rx_h_data(struct ieee80211_rx_data *rx)
}

static ieee80211_rx_result debug_noinline
ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx, struct sk_buff_head *frames)
ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx)
{
struct ieee80211_local *local = rx->local;
struct ieee80211_hw *hw = &local->hw;
Expand Down Expand Up @@ -1971,8 +1965,7 @@ ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx, struct sk_buff_head *frames)

spin_lock(&tid_agg_rx->reorder_lock);
/* release stored frames up to start of BAR */
ieee80211_release_reorder_frames(hw, tid_agg_rx, start_seq_num,
frames);
ieee80211_release_reorder_frames(hw, tid_agg_rx, start_seq_num);
spin_unlock(&tid_agg_rx->reorder_lock);

kfree_skb(skb);
Expand Down Expand Up @@ -2489,8 +2482,7 @@ static void ieee80211_rx_handlers_result(struct ieee80211_rx_data *rx,
}
}

static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
struct sk_buff_head *frames)
static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx)
{
ieee80211_rx_result res = RX_DROP_MONITOR;
struct sk_buff *skb;
Expand All @@ -2502,7 +2494,15 @@ static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
goto rxh_next; \
} while (0);

while ((skb = __skb_dequeue(frames))) {
spin_lock(&rx->local->rx_skb_queue.lock);
if (rx->local->running_rx_handler)
goto unlock;

rx->local->running_rx_handler = true;

while ((skb = __skb_dequeue(&rx->local->rx_skb_queue))) {
spin_unlock(&rx->local->rx_skb_queue.lock);

/*
* all the other fields are valid across frames
* that belong to an aMPDU since they are on the
Expand All @@ -2525,12 +2525,7 @@ static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
CALL_RXH(ieee80211_rx_h_mesh_fwding);
#endif
CALL_RXH(ieee80211_rx_h_data)

/* special treatment -- needs the queue */
res = ieee80211_rx_h_ctrl(rx, frames);
if (res != RX_CONTINUE)
goto rxh_next;

CALL_RXH(ieee80211_rx_h_ctrl);
CALL_RXH(ieee80211_rx_h_mgmt_check)
CALL_RXH(ieee80211_rx_h_action)
CALL_RXH(ieee80211_rx_h_userspace_mgmt)
Expand All @@ -2539,18 +2534,20 @@ static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,

rxh_next:
ieee80211_rx_handlers_result(rx, res);

spin_lock(&rx->local->rx_skb_queue.lock);
#undef CALL_RXH
}

rx->local->running_rx_handler = false;

unlock:
spin_unlock(&rx->local->rx_skb_queue.lock);
}

static void ieee80211_invoke_rx_handlers(struct ieee80211_rx_data *rx)
{
struct sk_buff_head reorder_release;
ieee80211_rx_result res = RX_DROP_MONITOR;

__skb_queue_head_init(&reorder_release);

#define CALL_RXH(rxh) \
do { \
res = rxh(rx); \
Expand All @@ -2561,9 +2558,9 @@ static void ieee80211_invoke_rx_handlers(struct ieee80211_rx_data *rx)
CALL_RXH(ieee80211_rx_h_passive_scan)
CALL_RXH(ieee80211_rx_h_check)

ieee80211_rx_reorder_ampdu(rx, &reorder_release);
ieee80211_rx_reorder_ampdu(rx);

ieee80211_rx_handlers(rx, &reorder_release);
ieee80211_rx_handlers(rx);
return;

rxh_next:
Expand All @@ -2578,7 +2575,6 @@ static void ieee80211_invoke_rx_handlers(struct ieee80211_rx_data *rx)
*/
void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
{
struct sk_buff_head frames;
struct ieee80211_rx_data rx = {
.sta = sta,
.sdata = sta->sdata,
Expand All @@ -2591,13 +2587,11 @@ void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
if (!tid_agg_rx)
return;

__skb_queue_head_init(&frames);

spin_lock(&tid_agg_rx->reorder_lock);
ieee80211_sta_reorder_release(&sta->local->hw, tid_agg_rx, &frames);
ieee80211_sta_reorder_release(&sta->local->hw, tid_agg_rx);
spin_unlock(&tid_agg_rx->reorder_lock);

ieee80211_rx_handlers(&rx, &frames);
ieee80211_rx_handlers(&rx);
}

/* main receive path */
Expand Down

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