[tip:timers/core] usb/gadget/NCM: Replace tasklet with softirq hrtimer

From: tip-bot for Thomas Gleixner
Date: Tue Jan 16 2018 - 05:28:11 EST


Commit-ID: b1a31a5f5f27ff8aba42b545a1c721941f735107
Gitweb: https://git.kernel.org/tip/b1a31a5f5f27ff8aba42b545a1c721941f735107
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Thu, 21 Dec 2017 11:42:04 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 16 Jan 2018 09:51:23 +0100

usb/gadget/NCM: Replace tasklet with softirq hrtimer

The tx_tasklet tasklet is used in invoke the hrtimer (task_timer) in
softirq context. This can be also achieved without the tasklet but
with HRTIMER_MODE_SOFT as hrtimer mode.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
Acked-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Felipe Balbi <balbi@xxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: keescook@xxxxxxxxxxxx
Cc: linux-usb@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20171221104205.7269-36-anna-maria@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
drivers/usb/gadget/function/f_ncm.c | 30 +++++++-----------------------
1 file changed, 7 insertions(+), 23 deletions(-)

diff --git a/drivers/usb/gadget/function/f_ncm.c b/drivers/usb/gadget/function/f_ncm.c
index c5bce8e..5780fba 100644
--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -73,9 +73,7 @@ struct f_ncm {
struct sk_buff *skb_tx_ndp;
u16 ndp_dgram_count;
bool timer_force_tx;
- struct tasklet_struct tx_tasklet;
struct hrtimer task_timer;
-
bool timer_stopping;
};

@@ -1104,7 +1102,7 @@ static struct sk_buff *ncm_wrap_ntb(struct gether *port,

/* Delay the timer. */
hrtimer_start(&ncm->task_timer, TX_TIMEOUT_NSECS,
- HRTIMER_MODE_REL);
+ HRTIMER_MODE_REL_SOFT);

/* Add the datagram position entries */
ntb_ndp = skb_put_zero(ncm->skb_tx_ndp, dgram_idx_len);
@@ -1148,17 +1146,15 @@ err:
}

/*
- * This transmits the NTB if there are frames waiting.
+ * The transmit should only be run if no skb data has been sent
+ * for a certain duration.
*/
-static void ncm_tx_tasklet(unsigned long data)
+static enum hrtimer_restart ncm_tx_timeout(struct hrtimer *data)
{
- struct f_ncm *ncm = (void *)data;
-
- if (ncm->timer_stopping)
- return;
+ struct f_ncm *ncm = container_of(data, struct f_ncm, task_timer);

/* Only send if data is available. */
- if (ncm->skb_tx_data) {
+ if (!ncm->timer_stopping && ncm->skb_tx_data) {
ncm->timer_force_tx = true;

/* XXX This allowance of a NULL skb argument to ndo_start_xmit
@@ -1171,16 +1167,6 @@ static void ncm_tx_tasklet(unsigned long data)

ncm->timer_force_tx = false;
}
-}
-
-/*
- * The transmit should only be run if no skb data has been sent
- * for a certain duration.
- */
-static enum hrtimer_restart ncm_tx_timeout(struct hrtimer *data)
-{
- struct f_ncm *ncm = container_of(data, struct f_ncm, task_timer);
- tasklet_schedule(&ncm->tx_tasklet);
return HRTIMER_NORESTART;
}

@@ -1513,8 +1499,7 @@ static int ncm_bind(struct usb_configuration *c, struct usb_function *f)
ncm->port.open = ncm_open;
ncm->port.close = ncm_close;

- tasklet_init(&ncm->tx_tasklet, ncm_tx_tasklet, (unsigned long) ncm);
- hrtimer_init(&ncm->task_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ hrtimer_init(&ncm->task_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT);
ncm->task_timer.function = ncm_tx_timeout;

DBG(cdev, "CDC Network: %s speed IN/%s OUT/%s NOTIFY/%s\n",
@@ -1623,7 +1608,6 @@ static void ncm_unbind(struct usb_configuration *c, struct usb_function *f)
DBG(c->cdev, "ncm unbind\n");

hrtimer_cancel(&ncm->task_timer);
- tasklet_kill(&ncm->tx_tasklet);

ncm_string_defs[0].id = 0;
usb_free_all_descriptors(f);