sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 343 insertions, 0 deletions

diff --git a/net/rfkill/input.c b/net/rfkill/input.c
new file mode 100644
index 000000000..f7cb24ce7
--- /dev/null
+++ b/net/rfkill/input.c
@@ -0,0 +1,343 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Input layer to RF Kill interface connector
+ *
+ * Copyright (c) 2007 Dmitry Torokhov
+ * Copyright 2009 Johannes Berg <johannes@sipsolutions.net>
+ *
+ * If you ever run into a situation in which you have a SW_ type rfkill
+ * input device, then you can revive code that was removed in the patch
+ * "rfkill-input: remove unused code".
+ */
+
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/moduleparam.h>
+#include <linux/workqueue.h>
+#include <linux/init.h>
+#include <linux/rfkill.h>
+#include <linux/sched.h>
+
+#include "rfkill.h"
+
+enum rfkill_input_master_mode {
+	RFKILL_INPUT_MASTER_UNLOCK = 0,
+	RFKILL_INPUT_MASTER_RESTORE = 1,
+	RFKILL_INPUT_MASTER_UNBLOCKALL = 2,
+	NUM_RFKILL_INPUT_MASTER_MODES
+};
+
+/* Delay (in ms) between consecutive switch ops */
+#define RFKILL_OPS_DELAY 200
+
+static enum rfkill_input_master_mode rfkill_master_switch_mode =
+					RFKILL_INPUT_MASTER_UNBLOCKALL;
+module_param_named(master_switch_mode, rfkill_master_switch_mode, uint, 0);
+MODULE_PARM_DESC(master_switch_mode,
+	"SW_RFKILL_ALL ON should: 0=do nothing (only unlock); 1=restore; 2=unblock all");
+
+static DEFINE_SPINLOCK(rfkill_op_lock);
+static bool rfkill_op_pending;
+static unsigned long rfkill_sw_pending[BITS_TO_LONGS(NUM_RFKILL_TYPES)];
+static unsigned long rfkill_sw_state[BITS_TO_LONGS(NUM_RFKILL_TYPES)];
+
+enum rfkill_sched_op {
+	RFKILL_GLOBAL_OP_EPO = 0,
+	RFKILL_GLOBAL_OP_RESTORE,
+	RFKILL_GLOBAL_OP_UNLOCK,
+	RFKILL_GLOBAL_OP_UNBLOCK,
+};
+
+static enum rfkill_sched_op rfkill_master_switch_op;
+static enum rfkill_sched_op rfkill_op;
+
+static void __rfkill_handle_global_op(enum rfkill_sched_op op)
+{
+	unsigned int i;
+
+	switch (op) {
+	case RFKILL_GLOBAL_OP_EPO:
+		rfkill_epo();
+		break;
+	case RFKILL_GLOBAL_OP_RESTORE:
+		rfkill_restore_states();
+		break;
+	case RFKILL_GLOBAL_OP_UNLOCK:
+		rfkill_remove_epo_lock();
+		break;
+	case RFKILL_GLOBAL_OP_UNBLOCK:
+		rfkill_remove_epo_lock();
+		for (i = 0; i < NUM_RFKILL_TYPES; i++)
+			rfkill_switch_all(i, false);
+		break;
+	default:
+		/* memory corruption or bug, fail safely */
+		rfkill_epo();
+		WARN(1, "Unknown requested operation %d! "
+			"rfkill Emergency Power Off activated\n",
+			op);
+	}
+}
+
+static void __rfkill_handle_normal_op(const enum rfkill_type type,
+				      const bool complement)
+{
+	bool blocked;
+
+	blocked = rfkill_get_global_sw_state(type);
+	if (complement)
+		blocked = !blocked;
+
+	rfkill_switch_all(type, blocked);
+}
+
+static void rfkill_op_handler(struct work_struct *work)
+{
+	unsigned int i;
+	bool c;
+
+	spin_lock_irq(&rfkill_op_lock);
+	do {
+		if (rfkill_op_pending) {
+			enum rfkill_sched_op op = rfkill_op;
+			rfkill_op_pending = false;
+			memset(rfkill_sw_pending, 0,
+				sizeof(rfkill_sw_pending));
+			spin_unlock_irq(&rfkill_op_lock);
+
+			__rfkill_handle_global_op(op);
+
+			spin_lock_irq(&rfkill_op_lock);
+
+			/*
+			 * handle global ops first -- during unlocked period
+			 * we might have gotten a new global op.
+			 */
+			if (rfkill_op_pending)
+				continue;
+		}
+
+		if (rfkill_is_epo_lock_active())
+			continue;
+
+		for (i = 0; i < NUM_RFKILL_TYPES; i++) {
+			if (__test_and_clear_bit(i, rfkill_sw_pending)) {
+				c = __test_and_clear_bit(i, rfkill_sw_state);
+				spin_unlock_irq(&rfkill_op_lock);
+
+				__rfkill_handle_normal_op(i, c);
+
+				spin_lock_irq(&rfkill_op_lock);
+			}
+		}
+	} while (rfkill_op_pending);
+	spin_unlock_irq(&rfkill_op_lock);
+}
+
+static DECLARE_DELAYED_WORK(rfkill_op_work, rfkill_op_handler);
+static unsigned long rfkill_last_scheduled;
+
+static unsigned long rfkill_ratelimit(const unsigned long last)
+{
+	const unsigned long delay = msecs_to_jiffies(RFKILL_OPS_DELAY);
+	return time_after(jiffies, last + delay) ? 0 : delay;
+}
+
+static void rfkill_schedule_ratelimited(void)
+{
+	if (schedule_delayed_work(&rfkill_op_work,
+				  rfkill_ratelimit(rfkill_last_scheduled)))
+		rfkill_last_scheduled = jiffies;
+}
+
+static void rfkill_schedule_global_op(enum rfkill_sched_op op)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&rfkill_op_lock, flags);
+	rfkill_op = op;
+	rfkill_op_pending = true;
+	if (op == RFKILL_GLOBAL_OP_EPO && !rfkill_is_epo_lock_active()) {
+		/* bypass the limiter for EPO */
+		mod_delayed_work(system_percpu_wq, &rfkill_op_work, 0);
+		rfkill_last_scheduled = jiffies;
+	} else
+		rfkill_schedule_ratelimited();
+	spin_unlock_irqrestore(&rfkill_op_lock, flags);
+}
+
+static void rfkill_schedule_toggle(enum rfkill_type type)
+{
+	unsigned long flags;
+
+	if (rfkill_is_epo_lock_active())
+		return;
+
+	spin_lock_irqsave(&rfkill_op_lock, flags);
+	if (!rfkill_op_pending) {
+		__set_bit(type, rfkill_sw_pending);
+		__change_bit(type, rfkill_sw_state);
+		rfkill_schedule_ratelimited();
+	}
+	spin_unlock_irqrestore(&rfkill_op_lock, flags);
+}
+
+static void rfkill_schedule_evsw_rfkillall(int state)
+{
+	if (state)
+		rfkill_schedule_global_op(rfkill_master_switch_op);
+	else
+		rfkill_schedule_global_op(RFKILL_GLOBAL_OP_EPO);
+}
+
+static void rfkill_event(struct input_handle *handle, unsigned int type,
+			unsigned int code, int data)
+{
+	if (type == EV_KEY && data == 1) {
+		switch (code) {
+		case KEY_WLAN:
+			rfkill_schedule_toggle(RFKILL_TYPE_WLAN);
+			break;
+		case KEY_BLUETOOTH:
+			rfkill_schedule_toggle(RFKILL_TYPE_BLUETOOTH);
+			break;
+		case KEY_UWB:
+			rfkill_schedule_toggle(RFKILL_TYPE_UWB);
+			break;
+		case KEY_WIMAX:
+			rfkill_schedule_toggle(RFKILL_TYPE_WIMAX);
+			break;
+		case KEY_RFKILL:
+			rfkill_schedule_toggle(RFKILL_TYPE_ALL);
+			break;
+		}
+	} else if (type == EV_SW && code == SW_RFKILL_ALL)
+		rfkill_schedule_evsw_rfkillall(data);
+}
+
+static int rfkill_connect(struct input_handler *handler, struct input_dev *dev,
+			  const struct input_device_id *id)
+{
+	struct input_handle *handle;
+	int error;
+
+	handle = kzalloc_obj(struct input_handle);
+	if (!handle)
+		return -ENOMEM;
+
+	handle->dev = dev;
+	handle->handler = handler;
+	handle->name = "rfkill";
+
+	/* causes rfkill_start() to be called */
+	error = input_register_handle(handle);
+	if (error)
+		goto err_free_handle;
+
+	error = input_open_device(handle);
+	if (error)
+		goto err_unregister_handle;
+
+	return 0;
+
+ err_unregister_handle:
+	input_unregister_handle(handle);
+ err_free_handle:
+	kfree(handle);
+	return error;
+}
+
+static void rfkill_start(struct input_handle *handle)
+{
+	/*
+	 * Take event_lock to guard against configuration changes, we
+	 * should be able to deal with concurrency with rfkill_event()
+	 * just fine (which event_lock will also avoid).
+	 */
+	spin_lock_irq(&handle->dev->event_lock);
+
+	if (test_bit(EV_SW, handle->dev->evbit) &&
+	    test_bit(SW_RFKILL_ALL, handle->dev->swbit))
+		rfkill_schedule_evsw_rfkillall(test_bit(SW_RFKILL_ALL,
+							handle->dev->sw));
+
+	spin_unlock_irq(&handle->dev->event_lock);
+}
+
+static void rfkill_disconnect(struct input_handle *handle)
+{
+	input_close_device(handle);
+	input_unregister_handle(handle);
+	kfree(handle);
+}
+
+static const struct input_device_id rfkill_ids[] = {
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = { [BIT_WORD(KEY_WLAN)] = BIT_MASK(KEY_WLAN) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = { [BIT_WORD(KEY_BLUETOOTH)] = BIT_MASK(KEY_BLUETOOTH) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = { [BIT_WORD(KEY_UWB)] = BIT_MASK(KEY_UWB) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = { [BIT_WORD(KEY_WIMAX)] = BIT_MASK(KEY_WIMAX) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_KEYBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+		.keybit = { [BIT_WORD(KEY_RFKILL)] = BIT_MASK(KEY_RFKILL) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT | INPUT_DEVICE_ID_MATCH_SWBIT,
+		.evbit = { BIT(EV_SW) },
+		.swbit = { [BIT_WORD(SW_RFKILL_ALL)] = BIT_MASK(SW_RFKILL_ALL) },
+	},
+	{ }
+};
+
+static struct input_handler rfkill_handler = {
+	.name =	"rfkill",
+	.event = rfkill_event,
+	.connect = rfkill_connect,
+	.start = rfkill_start,
+	.disconnect = rfkill_disconnect,
+	.id_table = rfkill_ids,
+};
+
+int __init rfkill_handler_init(void)
+{
+	switch (rfkill_master_switch_mode) {
+	case RFKILL_INPUT_MASTER_UNBLOCKALL:
+		rfkill_master_switch_op = RFKILL_GLOBAL_OP_UNBLOCK;
+		break;
+	case RFKILL_INPUT_MASTER_RESTORE:
+		rfkill_master_switch_op = RFKILL_GLOBAL_OP_RESTORE;
+		break;
+	case RFKILL_INPUT_MASTER_UNLOCK:
+		rfkill_master_switch_op = RFKILL_GLOBAL_OP_UNLOCK;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* Avoid delay at first schedule */
+	rfkill_last_scheduled =
+			jiffies - msecs_to_jiffies(RFKILL_OPS_DELAY) - 1;
+	return input_register_handler(&rfkill_handler);
+}
+
+void __exit rfkill_handler_exit(void)
+{
+	input_unregister_handler(&rfkill_handler);
+	cancel_delayed_work_sync(&rfkill_op_work);
+}