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Subject[PATCH 24/25 v2] net/cdc_ncm: Replace tasklet with softirq hrtimer
From: Thomas Gleixner <tglx@linutronix.de>

The bh tasklet is used in invoke the hrtimer (cdc_ncm_tx_timer_cb) in
softirq context. This can be also achieved without the tasklet but with
CLOCK_MONOTONIC_SOFT as hrtimer base.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Oliver Neukum <oliver@neukum.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-usb@vger.kernel.org
Cc: netdev@vger.kernel.org
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bigeasy: using usb_get_intfdata() as suggested by Bjørn Mork]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
On 2017-08-31 15:57:04 [+0200], Bjørn Mork wrote:
> I believe the struct usbnet pointer is redundant. We already have lots
> of pointers back and forth here. This should work, but is not tested:
>
> struct usbnet *dev = usb_get_intfdata(ctx->control):

I think so, too. Still untested as I don't have a working gadget around.

v1…v2: Updated as suggested by Bjørn and added Greg's Acked-by.

drivers/net/usb/cdc_ncm.c | 36 +++++++++++++++---------------------
include/linux/usb/cdc_ncm.h | 1 -
2 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 8f572b9f3625..42f7bd90e6a4 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -61,7 +61,6 @@ static bool prefer_mbim;
module_param(prefer_mbim, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(prefer_mbim, "Prefer MBIM setting on dual NCM/MBIM functions");

-static void cdc_ncm_txpath_bh(unsigned long param);
static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx);
static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *hr_timer);
static struct usb_driver cdc_ncm_driver;
@@ -777,10 +776,8 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
if (!ctx)
return -ENOMEM;

- hrtimer_init(&ctx->tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ hrtimer_init(&ctx->tx_timer, CLOCK_MONOTONIC_SOFT, HRTIMER_MODE_REL);
ctx->tx_timer.function = &cdc_ncm_tx_timer_cb;
- ctx->bh.data = (unsigned long)dev;
- ctx->bh.func = cdc_ncm_txpath_bh;
atomic_set(&ctx->stop, 0);
spin_lock_init(&ctx->mtx);

@@ -967,10 +964,7 @@ void cdc_ncm_unbind(struct usbnet *dev, struct usb_interface *intf)

atomic_set(&ctx->stop, 1);

- if (hrtimer_active(&ctx->tx_timer))
- hrtimer_cancel(&ctx->tx_timer);
-
- tasklet_kill(&ctx->bh);
+ hrtimer_cancel(&ctx->tx_timer);

/* handle devices with combined control and data interface */
if (ctx->control == ctx->data)
@@ -1348,20 +1342,9 @@ static void cdc_ncm_tx_timeout_start(struct cdc_ncm_ctx *ctx)
HRTIMER_MODE_REL);
}

-static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *timer)
+static void cdc_ncm_txpath_bh(struct cdc_ncm_ctx *ctx)
{
- struct cdc_ncm_ctx *ctx =
- container_of(timer, struct cdc_ncm_ctx, tx_timer);
-
- if (!atomic_read(&ctx->stop))
- tasklet_schedule(&ctx->bh);
- return HRTIMER_NORESTART;
-}
-
-static void cdc_ncm_txpath_bh(unsigned long param)
-{
- struct usbnet *dev = (struct usbnet *)param;
- struct cdc_ncm_ctx *ctx = (struct cdc_ncm_ctx *)dev->data[0];
+ struct usbnet *dev = usb_get_intfdata(ctx->control);

spin_lock_bh(&ctx->mtx);
if (ctx->tx_timer_pending != 0) {
@@ -1379,6 +1362,17 @@ static void cdc_ncm_txpath_bh(unsigned long param)
}
}

+static enum hrtimer_restart cdc_ncm_tx_timer_cb(struct hrtimer *timer)
+{
+ struct cdc_ncm_ctx *ctx =
+ container_of(timer, struct cdc_ncm_ctx, tx_timer);
+
+ if (!atomic_read(&ctx->stop))
+ cdc_ncm_txpath_bh(ctx);
+
+ return HRTIMER_NORESTART;
+}
+
struct sk_buff *
cdc_ncm_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
{
diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index 1a59699cf82a..62b506fddf8d 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -92,7 +92,6 @@
struct cdc_ncm_ctx {
struct usb_cdc_ncm_ntb_parameters ncm_parm;
struct hrtimer tx_timer;
- struct tasklet_struct bh;

const struct usb_cdc_ncm_desc *func_desc;
const struct usb_cdc_mbim_desc *mbim_desc;
--
2.14.1
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