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Subject[PATCH v2 02/50] wilc1000: switch txq_event from completion to waitqueue
Date
Completion structs are essentially counting semaphores: every
complete() call wakes up exactly one thread, either immediately (when
there are waiters queued) or in the future (when a waiter arrives).
This isn't really the appropriate synchronization structure for the
wilc1000 transmit queue handler (wilc_wlan_handle_txq) because it will
consume zero, one, or more packets on each call. Instead, use a
waitqueue as a condition variable: wake_up_interruptible() wakes up
the tx queue handler from a call to wait_event_interruptible()
whenever something interesting happens and it then takes the
appropriate action. This has a couple of benefits:

- Since the transmit queue handler often transfers multiple packets
to the chip on each call, repeated calls to wait_for_completion()
when there is no actual work to do are avoided.

- When the transmit queue handler cannot transfer any packets at all,
it'll simply give up the current time slice and then tries again.
Previously, the transmit would stall until a new packet showed up
(which potentially could cause extended stalls). It would be even
better to wait for a "tx queue not full" interrupt but, sadly, I'm
told the wilc1000 firmware doesn't provide that.

- There is no longer any need for wilc_wlan_txq_filter_dup_tcp_ack()
to adjust the completion structs wait count by calling
wait_for_completion_timeout() for each dropped packet.

Signed-off-by: David Mosberger-Tang <davidm@egauge.net>
---
drivers/net/wireless/microchip/wilc1000/cfg80211.c | 2 +-
drivers/net/wireless/microchip/wilc1000/netdev.c | 13 +++++++++----
drivers/net/wireless/microchip/wilc1000/netdev.h | 2 +-
drivers/net/wireless/microchip/wilc1000/wlan.c | 12 ++----------
4 files changed, 13 insertions(+), 16 deletions(-)

diff --git a/drivers/net/wireless/microchip/wilc1000/cfg80211.c b/drivers/net/wireless/microchip/wilc1000/cfg80211.c
index 8d8378bafd9b0..be387a8abb6af 100644
--- a/drivers/net/wireless/microchip/wilc1000/cfg80211.c
+++ b/drivers/net/wireless/microchip/wilc1000/cfg80211.c
@@ -1692,7 +1692,7 @@ static void wlan_init_locks(struct wilc *wl)
spin_lock_init(&wl->txq_spinlock);
mutex_init(&wl->txq_add_to_head_cs);

- init_completion(&wl->txq_event);
+ init_waitqueue_head(&wl->txq_event);
init_completion(&wl->cfg_event);
init_completion(&wl->sync_event);
init_completion(&wl->txq_thread_started);
diff --git a/drivers/net/wireless/microchip/wilc1000/netdev.c b/drivers/net/wireless/microchip/wilc1000/netdev.c
index 643bddaae32ad..d5969f2e369c4 100644
--- a/drivers/net/wireless/microchip/wilc1000/netdev.c
+++ b/drivers/net/wireless/microchip/wilc1000/netdev.c
@@ -144,10 +144,12 @@ static int wilc_txq_task(void *vp)
int ret;
u32 txq_count;
struct wilc *wl = vp;
+ long timeout;

complete(&wl->txq_thread_started);
while (1) {
- wait_for_completion(&wl->txq_event);
+ wait_event_interruptible(wl->txq_event,
+ (wl->txq_entries > 0 || wl->close));

if (wl->close) {
complete(&wl->txq_thread_started);
@@ -170,6 +172,11 @@ static int wilc_txq_task(void *vp)
}
srcu_read_unlock(&wl->srcu, srcu_idx);
}
+ if (ret == WILC_VMM_ENTRY_FULL_RETRY) {
+ timeout = msecs_to_jiffies(1);
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(timeout);
+ }
} while (ret == WILC_VMM_ENTRY_FULL_RETRY && !wl->close);
}
return 0;
@@ -419,12 +426,11 @@ static void wlan_deinitialize_threads(struct net_device *dev)

wl->close = 1;

- complete(&wl->txq_event);
-
if (wl->txq_thread) {
kthread_stop(wl->txq_thread);
wl->txq_thread = NULL;
}
+ wake_up_interruptible(&wl->txq_event);
}

static void wilc_wlan_deinitialize(struct net_device *dev)
@@ -446,7 +452,6 @@ static void wilc_wlan_deinitialize(struct net_device *dev)
wl->hif_func->disable_interrupt(wl);
mutex_unlock(&wl->hif_cs);
}
- complete(&wl->txq_event);

wlan_deinitialize_threads(dev);
deinit_irq(dev);
diff --git a/drivers/net/wireless/microchip/wilc1000/netdev.h b/drivers/net/wireless/microchip/wilc1000/netdev.h
index f4fc2cc392bd0..c07f58a86bc76 100644
--- a/drivers/net/wireless/microchip/wilc1000/netdev.h
+++ b/drivers/net/wireless/microchip/wilc1000/netdev.h
@@ -237,7 +237,7 @@ struct wilc {

struct completion cfg_event;
struct completion sync_event;
- struct completion txq_event;
+ wait_queue_head_t txq_event;
struct completion txq_thread_started;

struct task_struct *txq_thread;
diff --git a/drivers/net/wireless/microchip/wilc1000/wlan.c b/drivers/net/wireless/microchip/wilc1000/wlan.c
index c4da14147dd04..26fa7078acffd 100644
--- a/drivers/net/wireless/microchip/wilc1000/wlan.c
+++ b/drivers/net/wireless/microchip/wilc1000/wlan.c
@@ -75,7 +75,7 @@ static void wilc_wlan_txq_add_to_tail(struct net_device *dev, u8 q_num,

spin_unlock_irqrestore(&wilc->txq_spinlock, flags);

- complete(&wilc->txq_event);
+ wake_up_interruptible(&wilc->txq_event);
}

static void wilc_wlan_txq_add_to_head(struct wilc_vif *vif, u8 q_num,
@@ -94,7 +94,7 @@ static void wilc_wlan_txq_add_to_head(struct wilc_vif *vif, u8 q_num,

spin_unlock_irqrestore(&wilc->txq_spinlock, flags);
mutex_unlock(&wilc->txq_add_to_head_cs);
- complete(&wilc->txq_event);
+ wake_up_interruptible(&wilc->txq_event);
}

#define NOT_TCP_ACK (-1)
@@ -196,7 +196,6 @@ static void wilc_wlan_txq_filter_dup_tcp_ack(struct net_device *dev)
struct wilc *wilc = vif->wilc;
struct tcp_ack_filter *f = &vif->ack_filter;
u32 i = 0;
- u32 dropped = 0;
unsigned long flags;

spin_lock_irqsave(&wilc->txq_spinlock, flags);
@@ -226,7 +225,6 @@ static void wilc_wlan_txq_filter_dup_tcp_ack(struct net_device *dev)
tqe->tx_complete_func(tqe->priv,
tqe->status);
kfree(tqe);
- dropped++;
}
}
}
@@ -239,12 +237,6 @@ static void wilc_wlan_txq_filter_dup_tcp_ack(struct net_device *dev)
f->pending_base = 0;

spin_unlock_irqrestore(&wilc->txq_spinlock, flags);
-
- while (dropped > 0) {
- wait_for_completion_timeout(&wilc->txq_event,
- msecs_to_jiffies(1));
- dropped--;
- }
}

void wilc_enable_tcp_ack_filter(struct wilc_vif *vif, bool value)
--
2.25.1
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