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

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Message-ID: <tip-b1a31a5f5f27ff8aba42b545a1c721941f735107@git.kernel.org>
Date:   Tue, 16 Jan 2018 02:23:40 -0800
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hch@....de, balbi@...nel.org, torvalds@...ux-foundation.org,
        john.stultz@...aro.org, hpa@...or.com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, felipe.balbi@...ux.intel.com,
        anna-maria@...utronix.de, mingo@...nel.org, peterz@...radead.org
Subject: [tip:timers/core] usb/gadget/NCM: Replace tasklet with softirq
 hrtimer

Commit-ID:  b1a31a5f5f27ff8aba42b545a1c721941f735107
Gitweb:     https://git.kernel.org/tip/b1a31a5f5f27ff8aba42b545a1c721941f735107
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Thu, 21 Dec 2017 11:42:04 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
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@...utronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
Acked-by: Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Felipe Balbi <balbi@...nel.org>
Cc: John Stultz <john.stultz@...aro.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: keescook@...omium.org
Cc: linux-usb@...r.kernel.org
Link: http://lkml.kernel.org/r/20171221104205.7269-36-anna-maria@linutronix.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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);