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can: gs_usb: add missing lock to protect struct timecounter::cycle_last

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The struct timecounter::cycle_last is a 64 bit variable, read by
timecounter_cyc2time(), and written by timecounter_read(). On 32 bit
architectures this is not atomic.

Add a spinlock to protect access to struct timecounter::cycle_last. In
the gs_usb_timestamp_read() callback the lock is dropped to execute a
sleeping synchronous USB transfer. This is safe, as the variable we
want to protect is accessed during this call.

Fixes: 45dfa45f52e6 ("can: gs_usb: add RX and TX hardware timestamp support")
Link: https://lore.kernel.org/all/20220920100416.959226-3-mkl@pengutronix.de
Cc: John Whittington <git@jbrengineering.co.uk>
Tested-by: John Whittington <git@jbrengineering.co.uk>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Marc Kleine-Budde 2022-09-19 09:53:45 +02:00
parent 593b5e2f5a
commit 29a8c9ec90
1 changed files with 18 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/net/can/usb/gs_usb.c
View File

@ -286,6 +286,7 @@ struct gs_can {
/* time counter for hardware timestamps */
struct cyclecounter cc;
struct timecounter tc;
spinlock_t tc_lock; /* spinlock to guard access tc->cycle_last */
struct delayed_work timestamp;
u32 feature;
@ -401,14 +402,18 @@ static inline int gs_usb_get_timestamp(const struct gs_can *dev,
return 0;
}
static u64 gs_usb_timestamp_read(const struct cyclecounter *cc)
static u64 gs_usb_timestamp_read(const struct cyclecounter *cc) __must_hold(&dev->tc_lock)
{
const struct gs_can *dev;
struct gs_can *dev = container_of(cc, struct gs_can, cc);
u32 timestamp = 0;
int err;
dev = container_of(cc, struct gs_can, cc);
lockdep_assert_held(&dev->tc_lock);
/* drop lock for synchronous USB transfer */
spin_unlock_bh(&dev->tc_lock);
err = gs_usb_get_timestamp(dev, &timestamp);
spin_lock_bh(&dev->tc_lock);
if (err)
netdev_err(dev->netdev,
"Error %d while reading timestamp. HW timestamps may be inaccurate.",
@ -423,19 +428,24 @@ static void gs_usb_timestamp_work(struct work_struct *work)
struct gs_can *dev;
dev = container_of(delayed_work, struct gs_can, timestamp);
spin_lock_bh(&dev->tc_lock);
timecounter_read(&dev->tc);
spin_unlock_bh(&dev->tc_lock);
schedule_delayed_work(&dev->timestamp,
GS_USB_TIMESTAMP_WORK_DELAY_SEC * HZ);
}
static void gs_usb_skb_set_timestamp(const struct gs_can *dev,
static void gs_usb_skb_set_timestamp(struct gs_can *dev,
struct sk_buff *skb, u32 timestamp)
{
struct skb_shared_hwtstamps *hwtstamps = skb_hwtstamps(skb);
u64 ns;
spin_lock_bh(&dev->tc_lock);
ns = timecounter_cyc2time(&dev->tc, timestamp);
spin_unlock_bh(&dev->tc_lock);
hwtstamps->hwtstamp = ns_to_ktime(ns);
}
@ -448,7 +458,10 @@ static void gs_usb_timestamp_init(struct gs_can *dev)
cc->shift = 32 - bits_per(NSEC_PER_SEC / GS_USB_TIMESTAMP_TIMER_HZ);
cc->mult = clocksource_hz2mult(GS_USB_TIMESTAMP_TIMER_HZ, cc->shift);
spin_lock_init(&dev->tc_lock);
spin_lock_bh(&dev->tc_lock);
timecounter_init(&dev->tc, &dev->cc, ktime_get_real_ns());
spin_unlock_bh(&dev->tc_lock);
INIT_DELAYED_WORK(&dev->timestamp, gs_usb_timestamp_work);
schedule_delayed_work(&dev->timestamp,
@ -485,7 +498,7 @@ static void gs_update_state(struct gs_can *dev, struct can_frame *cf)
}
}
static void gs_usb_set_timestamp(const struct gs_can *dev, struct sk_buff *skb,
static void gs_usb_set_timestamp(struct gs_can *dev, struct sk_buff *skb,
const struct gs_host_frame *hf)
{
u32 timestamp;