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wusbcore: reduce keepalive threshold from timeout/2 to timeout/3

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This patch reduces the keepalive threshold of WUSB host controllers from
timeout/2 to timeout/3.  The keepalive timer fires every timeout/2 ms, but
due to rounding errors and jitter, the host may decide not to send a
keepalive at timeout/2.  By the time the next timer fires, a full timeout
period may have expired causing the device to be disconnected without ever
having been sent a keepalive.  Changing the keepalive threshold to
timeout/3 ensures that at least one keepalive will be sent before a device
is disconnected.  The patch also updates the code to use msecs_to_jiffies
consistently.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Pugliese 2013-06-06 10:40:49 -05:00 committed by Greg Kroah-Hartman
parent d9ea21a779
commit 7d9852a88c
2 changed files with 5 additions and 6 deletions
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6
drivers/usb/wusbcore/devconnect.c
View file

@ -455,8 +455,8 @@ static void __wusbhc_keep_alive(struct wusbhc *wusbhc)
dev_err(dev, "KEEPALIVE: device %u timed out\n",
wusb_dev->addr);
__wusbhc_dev_disconnect(wusbhc, wusb_port);
} else if (time_after(jiffies, wusb_dev->entry_ts + tt/2)) {
/* Approaching timeout cut out, need to refresh */
} else if (time_after(jiffies, wusb_dev->entry_ts + tt/3)) {
/* Approaching timeout cut off, need to refresh */
ie->bDeviceAddress[keep_alives++] = wusb_dev->addr;
}
}
@ -1062,7 +1062,7 @@ int wusbhc_devconnect_start(struct wusbhc *wusbhc)
wusbhc->wuie_host_info = hi;
queue_delayed_work(wusbd, &wusbhc->keep_alive_timer,
(wusbhc->trust_timeout*CONFIG_HZ)/1000/2);
msecs_to_jiffies(wusbhc->trust_timeout / 2));
return 0;

5
drivers/usb/wusbcore/wusbhc.c
View file

@ -75,12 +75,11 @@ static ssize_t wusb_trust_timeout_store(struct device *dev,
result = -EINVAL;
goto out;
}
/* FIXME: maybe we should check for range validity? */
wusbhc->trust_timeout = trust_timeout;
wusbhc->trust_timeout = min_t(unsigned, trust_timeout, 500);
cancel_delayed_work(&wusbhc->keep_alive_timer);
flush_workqueue(wusbd);
queue_delayed_work(wusbd, &wusbhc->keep_alive_timer,
(trust_timeout * CONFIG_HZ)/1000/2);
msecs_to_jiffies(wusbhc->trust_timeout / 2));
out:
return result < 0 ? result : size;
}