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Revision 2bbd00aef0671bfe3c2ca5ba67097246257de125 authored by Johannes Weiner on 26 February 2021, 01:16:47 UTC, committed by Linus Torvalds on 26 February 2021, 17:41:00 UTC 
mm: vmstat: fix NOHZ wakeups for node stat changes
 
On NOHZ, the periodic vmstat flushers on each CPU can go to sleep and
won't wake up until stat changes are detected in the per-cpu deltas of the
zone vmstat counters.

In commit 75ef71840539 ("mm, vmstat: add infrastructure for per-node
vmstats") per-node counters were introduced, and subsequently most stats
were moved from the zone to the node level.  However, the node counters
weren't added to the NOHZ wakeup detection.

In theory this can cause per-cpu errors to remain in the user-reported
stats indefinitely.  In practice this only affects a handful of sub
counters (file_mapped, dirty and writeback e.g.) because other page state
changes at the node level likely involve a change at the zone level as
well (alloc and free, lru ops).  Also, nobody has complained.

Fix it up for completeness: wake up vmstat refreshing on node changes.
Also remove the BUILD_BUG_ONs that assert counter size; we haven't relied
on it since we added sizeof() to the range calculation in commit
13c9aaf7fa01 ("mm/vmstat.c: fix NUMA statistics updates").

Link: https://lkml.kernel.org/r/20210202184342.118513-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent a052d4d
Raw File
hid-speedlink.c 
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  HID driver for Speedlink Vicious and Divine Cezanne (USB mouse).
 *  Fixes "jumpy" cursor and removes nonexistent keyboard LEDS from
 *  the HID descriptor.
 *
 *  Copyright (c) 2011, 2013 Stefan Kriwanek <dev@stefankriwanek.de>
 */

/*
 */

#include <linux/device.h>
#include <linux/hid.h>
#include <linux/module.h>

#include "hid-ids.h"

static const struct hid_device_id speedlink_devices[] = {
	{ HID_USB_DEVICE(USB_VENDOR_ID_X_TENSIONS, USB_DEVICE_ID_SPEEDLINK_VAD_CEZANNE)},
	{ }
};

static int speedlink_input_mapping(struct hid_device *hdev,
		struct hid_input *hi,
		struct hid_field *field, struct hid_usage *usage,
		unsigned long **bit, int *max)
{
	/*
	 * The Cezanne mouse has a second "keyboard" USB endpoint for it is
	 * able to map keyboard events to the button presses.
	 * It sends a standard keyboard report descriptor, though, whose
	 * LEDs we ignore.
	 */
	switch (usage->hid & HID_USAGE_PAGE) {
	case HID_UP_LED:
		return -1;
	}
	return 0;
}

static int speedlink_event(struct hid_device *hdev, struct hid_field *field,
		struct hid_usage *usage, __s32 value)
{
	/* No other conditions due to usage_table. */

	/* This fixes the "jumpy" cursor occuring due to invalid events sent
	 * by the device. Some devices only send them with value==+256, others
	 * don't. However, catching abs(value)>=256 is restrictive enough not
	 * to interfere with devices that were bug-free (has been tested).
	 */
	if (abs(value) >= 256)
		return 1;
	/* Drop useless distance 0 events (on button clicks etc.) as well */
	if (value == 0)
		return 1;

	return 0;
}

MODULE_DEVICE_TABLE(hid, speedlink_devices);

static const struct hid_usage_id speedlink_grabbed_usages[] = {
	{ HID_GD_X, EV_REL, 0 },
	{ HID_GD_Y, EV_REL, 1 },
	{ HID_ANY_ID - 1, HID_ANY_ID - 1, HID_ANY_ID - 1}
};

static struct hid_driver speedlink_driver = {
	.name = "speedlink",
	.id_table = speedlink_devices,
	.usage_table = speedlink_grabbed_usages,
	.input_mapping = speedlink_input_mapping,
	.event = speedlink_event,
};
module_hid_driver(speedlink_driver);

MODULE_LICENSE("GPL");
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