tracing: Last minute updates for 5.14

index ad31ec4ad627..6d8d4bf20837 100644
@@ -49,7 +49,7 @@ static int __init copy_xbc_key_value_list(char *dst, size_t size)
 				else
 					q = '"';
 				ret = snprintf(dst, rest(dst, end), "%c%s%c%s",
-					q, val, q, vnode->next ? ", " : "\n");
+					q, val, q, xbc_node_is_array(vnode) ? ", " : "\n");
 				if (ret < 0)
 					goto out;
 				dst += ret;

index 2696eb0fc149..3178a31fdabc 100644
@@ -71,7 +71,7 @@ static inline __init bool xbc_node_is_key(struct xbc_node *node)
  */
 static inline __init bool xbc_node_is_array(struct xbc_node *node)
 {
-	return xbc_node_is_value(node) && node->next != 0;
+	return xbc_node_is_value(node) && node->child != 0;
 }
 
 /**

@@ -140,7 +140,7 @@ static inline struct xbc_node * __init xbc_find_node(const char *key)
  */
 #define xbc_array_for_each_value(anode, value)				\
 	for (value = xbc_node_get_data(anode); anode != NULL ;		\
-	     anode = xbc_node_get_next(anode),				\
+	     anode = xbc_node_get_child(anode),				\
 	     value = anode ? xbc_node_get_data(anode) : NULL)
 
 /**

@@ -171,7 +171,7 @@ static inline struct xbc_node * __init xbc_find_node(const char *key)
  */
 #define xbc_node_for_each_array_value(node, key, anode, value)		\
 	for (value = xbc_node_find_value(node, key, &anode); value != NULL; \
-	     anode = xbc_node_get_next(anode),				\
+	     anode = xbc_node_get_child(anode),				\
 	     value = anode ? xbc_node_get_data(anode) : NULL)
 
 /**

index 9f8c70a98fcf..44dcdcbd746a 100644
@@ -367,6 +367,14 @@ static inline __init struct xbc_node *xbc_last_sibling(struct xbc_node *node)
 	return node;
 }
 
+static inline __init struct xbc_node *xbc_last_child(struct xbc_node *node)
+{
+	while (node->child)
+		node = xbc_node_get_child(node);
+
+	return node;
+}
+
 static struct xbc_node * __init xbc_add_sibling(char *data, u32 flag)
 {
 	struct xbc_node *sib, *node = xbc_add_node(data, flag);

@@ -517,17 +525,20 @@ static int __init xbc_parse_array(char **__v)
 	char *next;
 	int c = 0;
 
+	if (last_parent->child)
+		last_parent = xbc_node_get_child(last_parent);
+
 	do {
 		c = __xbc_parse_value(__v, &next);
 		if (c < 0)
 			return c;
 
-		node = xbc_add_sibling(*__v, XBC_VALUE);
+		node = xbc_add_child(*__v, XBC_VALUE);
 		if (!node)
 			return -ENOMEM;
 		*__v = next;
 	} while (c == ',');
-	node->next = 0;
+	node->child = 0;
 
 	return c;
 }

@@ -615,8 +626,12 @@ static int __init xbc_parse_kv(char **k, char *v, int op)
 
 	if (op == ':' && child) {
 		xbc_init_node(child, v, XBC_VALUE);
-	} else if (!xbc_add_sibling(v, XBC_VALUE))
-		return -ENOMEM;
+	} else {
+		if (op == '+' && child)
+			last_parent = xbc_last_child(child);
+		if (!xbc_add_sibling(v, XBC_VALUE))
+			return -ENOMEM;
+	}
 
 	if (c == ',') {	/* Array */
 		c = xbc_parse_array(&next);

index 268b72f4cc92..23569fb634f1 100644
@@ -27,7 +27,7 @@ static int xbc_show_value(struct xbc_node *node, bool semicolon)
 			q = '\'';
 		else
 			q = '"';
-		printf("%c%s%c%s", q, val, q, node->next ? ", " : eol);
+		printf("%c%s%c%s", q, val, q, xbc_node_is_array(node) ? ", " : eol);
 		i++;
 	}
 	return i;

index 3178a31fdabc..e49043ac77c9 100644
@@ -80,6 +80,8 @@ static inline __init bool xbc_node_is_array(struct xbc_node *node)
  *
  * Test the @node is a leaf key node which is a key node and has a value node
  * or no child. Returns true if it is a leaf node, or false if not.
+ * Note that the leaf node can have subkey nodes in addition to the
+ * value node.
  */
 static inline __init bool xbc_node_is_leaf(struct xbc_node *node)
 {

@@ -129,6 +131,23 @@ static inline struct xbc_node * __init xbc_find_node(const char *key)
 	return xbc_node_find_child(NULL, key);
 }
 
+/**
+ * xbc_node_get_subkey() - Return the first subkey node if exists
+ * @node: Parent node
+ *
+ * Return the first subkey node of the @node. If the @node has no child
+ * or only value node, this will return NULL.
+ */
+static inline struct xbc_node * __init xbc_node_get_subkey(struct xbc_node *node)
+{
+	struct xbc_node *child = xbc_node_get_child(node);
+
+	if (child && xbc_node_is_value(child))
+		return xbc_node_get_next(child);
+	else
+		return child;
+}
+
 /**
  * xbc_array_for_each_value() - Iterate value nodes on an array
  * @anode: An XBC arraied value node

@@ -149,11 +168,24 @@ static inline struct xbc_node * __init xbc_find_node(const char *key)
  * @child: Iterated XBC node.
  *
  * Iterate child nodes of @parent. Each child nodes are stored to @child.
+ * The @child can be mixture of a value node and subkey nodes.
  */
 #define xbc_node_for_each_child(parent, child)				\
 	for (child = xbc_node_get_child(parent); child != NULL ;	\
 	     child = xbc_node_get_next(child))
 
+/**
+ * xbc_node_for_each_subkey() - Iterate child subkey nodes
+ * @parent: An XBC node.
+ * @child: Iterated XBC node.
+ *
+ * Iterate subkey nodes of @parent. Each child nodes are stored to @child.
+ * The @child is only the subkey node.
+ */
+#define xbc_node_for_each_subkey(parent, child)				\
+	for (child = xbc_node_get_subkey(parent); child != NULL ;	\
+	     child = xbc_node_get_next(child))
+
 /**
  * xbc_node_for_each_array_value() - Iterate array entries of geven key
  * @node: An XBC node.

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index e49043ac77c9..6bdd94cff4e2 100644
@@ -16,6 +16,26 @@
 #define BOOTCONFIG_ALIGN	(1 << BOOTCONFIG_ALIGN_SHIFT)
 #define BOOTCONFIG_ALIGN_MASK	(BOOTCONFIG_ALIGN - 1)
 
+/**
+ * xbc_calc_checksum() - Calculate checksum of bootconfig
+ * @data: Bootconfig data.
+ * @size: The size of the bootconfig data.
+ *
+ * Calculate the checksum value of the bootconfig data.
+ * The checksum will be used with the BOOTCONFIG_MAGIC and the size for
+ * embedding the bootconfig in the initrd image.
+ */
+static inline __init u32 xbc_calc_checksum(void *data, u32 size)
+{
+	unsigned char *p = data;
+	u32 ret = 0;
+
+	while (size--)
+		ret += *p++;
+
+	return ret;
+}
+
 /* XBC tree node */
 struct xbc_node {
 	u16 next;

index e9c42a183e33..7b150f0501e2 100644
@@ -386,16 +386,6 @@ static char * __init xbc_make_cmdline(const char *key)
 	return new_cmdline;
 }
 
-static u32 boot_config_checksum(unsigned char *p, u32 size)
-{
-	u32 ret = 0;
-
-	while (size--)
-		ret += *p++;
-
-	return ret;
-}
-
 static int __init bootconfig_params(char *param, char *val,
 				    const char *unused, void *arg)
 {

@@ -439,7 +429,7 @@ static void __init setup_boot_config(void)
 		return;
 	}
 
-	if (boot_config_checksum((unsigned char *)data, size) != csum) {
+	if (xbc_calc_checksum(data, size) != csum) {
 		pr_err("bootconfig checksum failed\n");
 		return;
 	}

index 62a3b5064b17..f45fa992e01d 100644
@@ -126,17 +126,6 @@ static void xbc_show_list(void)
 	}
 }
 
-/* Simple real checksum */
-static int checksum(unsigned char *buf, int len)
-{
-	int i, sum = 0;
-
-	for (i = 0; i < len; i++)
-		sum += buf[i];
-
-	return sum;
-}
-
 #define PAGE_SIZE	4096
 
 static int load_xbc_fd(int fd, char **buf, int size)

@@ -232,7 +221,7 @@ static int load_xbc_from_initrd(int fd, char **buf)
 		return ret;
 
 	/* Wrong Checksum */
-	rcsum = checksum((unsigned char *)*buf, size);
+	rcsum = xbc_calc_checksum(*buf, size);
 	if (csum != rcsum) {
 		pr_err("checksum error: %d != %d\n", csum, rcsum);
 		return -EINVAL;

@@ -381,7 +370,7 @@ static int apply_xbc(const char *path, const char *xbc_path)
 		return ret;
 	}
 	size = strlen(buf) + 1;
-	csum = checksum((unsigned char *)buf, size);
+	csum = xbc_calc_checksum(buf, size);
 
 	/* Backup the bootconfig data */
 	data = calloc(size + BOOTCONFIG_ALIGN +

index 2e592885a167..a0a84ff46ecd 100644
@@ -2735,8 +2735,10 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb,
 	    (trace_file->flags & (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
 	    (entry = this_cpu_read(trace_buffered_event))) {
 		/* Try to use the per cpu buffer first */
+		int max_len = PAGE_SIZE - struct_size(entry, array, 1);
+
 		val = this_cpu_inc_return(trace_buffered_event_cnt);
-		if ((len < (PAGE_SIZE - sizeof(*entry) - sizeof(entry->array[0]))) && val == 1) {
+		if (val == 1 && likely(len <= max_len)) {
 			trace_event_setup(entry, type, trace_ctx);
 			entry->array[0] = len;
 			return entry;

index a0a84ff46ecd..a0d66a056e59 100644
@@ -2734,10 +2734,44 @@ trace_event_buffer_lock_reserve(struct trace_buffer **current_rb,
 	if (!tr->no_filter_buffering_ref &&
 	    (trace_file->flags & (EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
 	    (entry = this_cpu_read(trace_buffered_event))) {
-		/* Try to use the per cpu buffer first */
+		/*
+		 * Filtering is on, so try to use the per cpu buffer first.
+		 * This buffer will simulate a ring_buffer_event,
+		 * where the type_len is zero and the array[0] will
+		 * hold the full length.
+		 * (see include/linux/ring-buffer.h for details on
+		 *  how the ring_buffer_event is structured).
+		 *
+		 * Using a temp buffer during filtering and copying it
+		 * on a matched filter is quicker than writing directly
+		 * into the ring buffer and then discarding it when
+		 * it doesn't match. That is because the discard
+		 * requires several atomic operations to get right.
+		 * Copying on match and doing nothing on a failed match
+		 * is still quicker than no copy on match, but having
+		 * to discard out of the ring buffer on a failed match.
+		 */
 		int max_len = PAGE_SIZE - struct_size(entry, array, 1);
 
 		val = this_cpu_inc_return(trace_buffered_event_cnt);
+
+		/*
+		 * Preemption is disabled, but interrupts and NMIs
+		 * can still come in now. If that happens after
+		 * the above increment, then it will have to go
+		 * back to the old method of allocating the event
+		 * on the ring buffer, and if the filter fails, it
+		 * will have to call ring_buffer_discard_commit()
+		 * to remove it.
+		 *
+		 * Need to also check the unlikely case that the
+		 * length is bigger than the temp buffer size.
+		 * If that happens, then the reserve is pretty much
+		 * guaranteed to fail, as the ring buffer currently
+		 * only allows events less than a page. But that may
+		 * change in the future, so let the ring buffer reserve
+		 * handle the failure in that case.
+		 */
 		if (val == 1 && likely(len <= max_len)) {
 			trace_event_setup(entry, type, trace_ctx);
 			entry->array[0] = len;

index a0d66a056e59..bbc63ac5b47f 100644
@@ -86,6 +86,7 @@ void __init disable_tracing_selftest(const char *reason)
 /* Pipe tracepoints to printk */
 struct trace_iterator *tracepoint_print_iter;
 int tracepoint_printk;
+static bool tracepoint_printk_stop_on_boot __initdata;
 static DEFINE_STATIC_KEY_FALSE(tracepoint_printk_key);
 
 /* For tracers that don't implement custom flags */

@@ -256,6 +257,13 @@ static int __init set_tracepoint_printk(char *str)
 }
 __setup("tp_printk", set_tracepoint_printk);
 
+static int __init set_tracepoint_printk_stop(char *str)
+{
+	tracepoint_printk_stop_on_boot = true;
+	return 1;
+}
+__setup("tp_printk_stop_on_boot", set_tracepoint_printk_stop);
+
 unsigned long long ns2usecs(u64 nsec)
 {
 	nsec += 500;

@@ -9578,6 +9586,8 @@ static __init int tracer_init_tracefs(void)
 	return 0;
 }
 
+fs_initcall(tracer_init_tracefs);
+
 static int trace_panic_handler(struct notifier_block *this,
 			       unsigned long event, void *unused)
 {

@@ -9998,7 +10008,7 @@ void __init trace_init(void)
 	trace_event_init();
 }
 
-__init static int clear_boot_tracer(void)
+__init static void clear_boot_tracer(void)
 {
 	/*
 	 * The default tracer at boot buffer is an init section.

@@ -10008,26 +10018,21 @@ __init static int clear_boot_tracer(void)
 	 * about to be freed.
 	 */
 	if (!default_bootup_tracer)
-		return 0;
+		return;
 
 	printk(KERN_INFO "ftrace bootup tracer '%s' not registered.\n",
 	       default_bootup_tracer);
 	default_bootup_tracer = NULL;
-
-	return 0;
 }
 
-fs_initcall(tracer_init_tracefs);
-late_initcall_sync(clear_boot_tracer);
-
 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
-__init static int tracing_set_default_clock(void)
+__init static void tracing_set_default_clock(void)
 {
 	/* sched_clock_stable() is determined in late_initcall */
 	if (!trace_boot_clock && !sched_clock_stable()) {
 		if (security_locked_down(LOCKDOWN_TRACEFS)) {
 			pr_warn("Can not set tracing clock due to lockdown\n");
-			return -EPERM;
+			return;
 		}
 
 		printk(KERN_WARNING

@@ -10037,8 +10042,21 @@ __init static int tracing_set_default_clock(void)
 		       "on the kernel command line\n");
 		tracing_set_clock(&global_trace, "global");
 	}
+}
+#else
+static inline void tracing_set_default_clock(void) { }
+#endif
 
+__init static int late_trace_init(void)
+{
+	if (tracepoint_printk && tracepoint_printk_stop_on_boot) {
+		static_key_disable(&tracepoint_printk_key.key);
+		tracepoint_printk = 0;
+	}
+
+	tracing_set_default_clock();
+	clear_boot_tracer();
 	return 0;
 }
-late_initcall_sync(tracing_set_default_clock);
-#endif
+
+late_initcall_sync(late_trace_init);

index bbc63ac5b47f..d352fb4b7709 100644
@@ -197,12 +197,12 @@ __setup("ftrace=", set_cmdline_ftrace);
 
 static int __init set_ftrace_dump_on_oops(char *str)
 {
-	if (*str++ != '=' || !*str) {
+	if (*str++ != '=' || !*str || !strcmp("1", str)) {
 		ftrace_dump_on_oops = DUMP_ALL;
 		return 1;
 	}
 
-	if (!strcmp("orig_cpu", str)) {
+	if (!strcmp("orig_cpu", str) || !strcmp("2", str)) {
 		ftrace_dump_on_oops = DUMP_ORIG;
                 return 1;
         }

index 632ef88131a9..0a5635401125 100644
@@ -34,7 +34,7 @@
  * Copyright (C) 2008-2009 Jon Masters, Red Hat, Inc. <[email protected]>
  * Copyright (C) 2013-2016 Steven Rostedt, Red Hat, Inc. <[email protected]>
  *
- * Includes useful feedback from Clark Williams <[email protected]>
+ * Includes useful feedback from Clark Williams <[email protected]>
  *
  */
 #include <linux/kthread.h>

250 lines not on this page · raw message

index 43a436d85a01..bae74b95cf55 100644
@@ -286,7 +286,6 @@ static int get_sample(void)
 }
 
 static struct cpumask save_cpumask;
-static bool disable_migrate;
 
 static void move_to_next_cpu(void)
 {

@@ -294,15 +293,13 @@ static void move_to_next_cpu(void)
 	struct trace_array *tr = hwlat_trace;
 	int next_cpu;
 
-	if (disable_migrate)
-		return;
 	/*
 	 * If for some reason the user modifies the CPU affinity
 	 * of this thread, then stop migrating for the duration
 	 * of the current test.
 	 */
 	if (!cpumask_equal(current_mask, current->cpus_ptr))
-		goto disable;
+		goto change_mode;
 
 	get_online_cpus();
 	cpumask_and(current_mask, cpu_online_mask, tr->tracing_cpumask);

@@ -313,7 +310,7 @@ static void move_to_next_cpu(void)
 		next_cpu = cpumask_first(current_mask);
 
 	if (next_cpu >= nr_cpu_ids) /* Shouldn't happen! */
-		goto disable;
+		goto change_mode;
 
 	cpumask_clear(current_mask);
 	cpumask_set_cpu(next_cpu, current_mask);

@@ -321,8 +318,9 @@ static void move_to_next_cpu(void)
 	sched_setaffinity(0, current_mask);
 	return;
 
- disable:
-	disable_migrate = true;
+ change_mode:
+	hwlat_data.thread_mode = MODE_NONE;
+	pr_info(BANNER "cpumask changed while in round-robin mode, switching to mode none\n");
 }
 
 /*

@@ -744,7 +742,6 @@ static int hwlat_tracer_init(struct trace_array *tr)
 
 	hwlat_trace = tr;
 
-	disable_migrate = false;
 	hwlat_data.count = 0;
 	tr->max_latency = 0;
 	save_tracing_thresh = tracing_thresh;

306 lines not on this page · raw message

index d352fb4b7709..27bf203ef05a 100644
@@ -7583,6 +7583,91 @@ static const struct file_operations snapshot_raw_fops = {
 
 #endif /* CONFIG_TRACER_SNAPSHOT */
 
+/*
+ * trace_min_max_write - Write a u64 value to a trace_min_max_param struct
+ * @filp: The active open file structure
+ * @ubuf: The userspace provided buffer to read value into
+ * @cnt: The maximum number of bytes to read
+ * @ppos: The current "file" position
+ *
+ * This function implements the write interface for a struct trace_min_max_param.
+ * The filp->private_data must point to a trace_min_max_param structure that
+ * defines where to write the value, the min and the max acceptable values,
+ * and a lock to protect the write.
+ */
+static ssize_t
+trace_min_max_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+	struct trace_min_max_param *param = filp->private_data;
+	u64 val;
+	int err;
+
+	if (!param)
+		return -EFAULT;
+
+	err = kstrtoull_from_user(ubuf, cnt, 10, &val);
+	if (err)
+		return err;
+
+	if (param->lock)
+		mutex_lock(param->lock);
+
+	if (param->min && val < *param->min)
+		err = -EINVAL;
+
+	if (param->max && val > *param->max)
+		err = -EINVAL;
+
+	if (!err)
+		*param->val = val;
+
+	if (param->lock)
+		mutex_unlock(param->lock);
+
+	if (err)
+		return err;
+
+	return cnt;
+}
+
+/*
+ * trace_min_max_read - Read a u64 value from a trace_min_max_param struct
+ * @filp: The active open file structure
+ * @ubuf: The userspace provided buffer to read value into
+ * @cnt: The maximum number of bytes to read
+ * @ppos: The current "file" position
+ *
+ * This function implements the read interface for a struct trace_min_max_param.
+ * The filp->private_data must point to a trace_min_max_param struct with valid
+ * data.
+ */
+static ssize_t
+trace_min_max_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+	struct trace_min_max_param *param = filp->private_data;
+	char buf[U64_STR_SIZE];
+	int len;
+	u64 val;
+
+	if (!param)
+		return -EFAULT;
+
+	val = *param->val;
+
+	if (cnt > sizeof(buf))
+		cnt = sizeof(buf);
+
+	len = snprintf(buf, sizeof(buf), "%llu\n", val);
+
+	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
+}
+
+const struct file_operations trace_min_max_fops = {
+	.open		= tracing_open_generic,
+	.read		= trace_min_max_read,
+	.write		= trace_min_max_write,
+};
+
 #define TRACING_LOG_ERRS_MAX	8
 #define TRACING_LOG_LOC_MAX	128
 

index cd80d046c7a5..22f8c652ef8b 100644
@@ -1952,4 +1952,22 @@ static inline bool is_good_name(const char *name)
 	return true;
 }
 
+/*
+ * This is a generic way to read and write a u64 value from a file in tracefs.
+ *
+ * The value is stored on the variable pointed by *val. The value needs
+ * to be at least *min and at most *max. The write is protected by an
+ * existing *lock.
+ */
+struct trace_min_max_param {
+	struct mutex	*lock;
+	u64		*val;
+	u64		*min;
+	u64		*max;
+};
+
+#define U64_STR_SIZE		24	/* 20 digits max */
+
+extern const struct file_operations trace_min_max_fops;
+
 #endif /* _LINUX_KERNEL_TRACE_H */

index 3957b36826e2..44f46bc1140f 100644
@@ -527,115 +527,6 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
 	return retval;
 }
 
-/*
- * hwlat_read - Wrapper read function for reading both window and width
- * @filp: The active open file structure
- * @ubuf: The userspace provided buffer to read value into
- * @cnt: The maximum number of bytes to read
- * @ppos: The current "file" position
- *
- * This function provides a generic read implementation for the global state
- * "hwlat_data" structure filesystem entries.
- */
-static ssize_t hwlat_read(struct file *filp, char __user *ubuf,
-			  size_t cnt, loff_t *ppos)
-{
-	char buf[U64STR_SIZE];
-	u64 *entry = filp->private_data;
-	u64 val;
-	int len;
-
-	if (!entry)
-		return -EFAULT;
-
-	if (cnt > sizeof(buf))
-		cnt = sizeof(buf);
-
-	val = *entry;
-
-	len = snprintf(buf, sizeof(buf), "%llu\n", val);
-
-	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
-}
-
-/**
- * hwlat_width_write - Write function for "width" entry
- * @filp: The active open file structure
- * @ubuf: The user buffer that contains the value to write
- * @cnt: The maximum number of bytes to write to "file"
- * @ppos: The current position in @file
- *
- * This function provides a write implementation for the "width" interface
- * to the hardware latency detector. It can be used to configure
- * for how many us of the total window us we will actively sample for any
- * hardware-induced latency periods. Obviously, it is not possible to
- * sample constantly and have the system respond to a sample reader, or,
- * worse, without having the system appear to have gone out to lunch. It
- * is enforced that width is less that the total window size.
- */
-static ssize_t
-hwlat_width_write(struct file *filp, const char __user *ubuf,
-		  size_t cnt, loff_t *ppos)
-{
-	u64 val;
-	int err;
-
-	err = kstrtoull_from_user(ubuf, cnt, 10, &val);
-	if (err)
-		return err;
-
-	mutex_lock(&hwlat_data.lock);
-	if (val < hwlat_data.sample_window)
-		hwlat_data.sample_width = val;
-	else
-		err = -EINVAL;
-	mutex_unlock(&hwlat_data.lock);
-
-	if (err)
-		return err;
-
-	return cnt;
-}
-
-/**
- * hwlat_window_write - Write function for "window" entry
- * @filp: The active open file structure
- * @ubuf: The user buffer that contains the value to write
- * @cnt: The maximum number of bytes to write to "file"
- * @ppos: The current position in @file
- *
- * This function provides a write implementation for the "window" interface
- * to the hardware latency detector. The window is the total time
- * in us that will be considered one sample period. Conceptually, windows
- * occur back-to-back and contain a sample width period during which
- * actual sampling occurs. Can be used to write a new total window size. It
- * is enforced that any value written must be greater than the sample width
- * size, or an error results.
- */
-static ssize_t
-hwlat_window_write(struct file *filp, const char __user *ubuf,
-		   size_t cnt, loff_t *ppos)
-{
-	u64 val;
-	int err;
-
-	err = kstrtoull_from_user(ubuf, cnt, 10, &val);
-	if (err)
-		return err;
-
-	mutex_lock(&hwlat_data.lock);
-	if (hwlat_data.sample_width < val)
-		hwlat_data.sample_window = val;
-	else
-		err = -EINVAL;
-	mutex_unlock(&hwlat_data.lock);
-
-	if (err)
-		return err;
-
-	return cnt;
-}
-
 static void *s_mode_start(struct seq_file *s, loff_t *pos)
 {
 	int mode = *pos;

@@ -760,16 +651,28 @@ static ssize_t hwlat_mode_write(struct file *filp, const char __user *ubuf,
 	return ret;
 }
 
-static const struct file_operations width_fops = {
-	.open		= tracing_open_generic,
-	.read		= hwlat_read,
-	.write		= hwlat_width_write,
+/*
+ * The width parameter is read/write using the generic trace_min_max_param
+ * method. The *val is protected by the hwlat_data lock and is upper
+ * bounded by the window parameter.
+ */
+static struct trace_min_max_param hwlat_width = {
+	.lock		= &hwlat_data.lock,
+	.val		= &hwlat_data.sample_width,
+	.max		= &hwlat_data.sample_window,
+	.min		= NULL,
 };
 
-static const struct file_operations window_fops = {
-	.open		= tracing_open_generic,
-	.read		= hwlat_read,
-	.write		= hwlat_window_write,
+/*
+ * The window parameter is read/write using the generic trace_min_max_param
+ * method. The *val is protected by the hwlat_data lock and is lower
+ * bounded by the width parameter.
+ */
+static struct trace_min_max_param hwlat_window = {
+	.lock		= &hwlat_data.lock,
+	.val		= &hwlat_data.sample_window,
+	.max		= NULL,
+	.min		= &hwlat_data.sample_width,
 };
 
 static const struct file_operations thread_mode_fops = {

@@ -802,15 +705,15 @@ static int init_tracefs(void)
 
 	hwlat_sample_window = tracefs_create_file("window", 0640,
 						  top_dir,
-						  &hwlat_data.sample_window,
-						  &window_fops);
+						  &hwlat_window,
+						  &trace_min_max_fops);
 	if (!hwlat_sample_window)
 		goto err;
 
 	hwlat_sample_width = tracefs_create_file("width", 0644,
 						 top_dir,
-						 &hwlat_data.sample_width,
-						 &width_fops);
+						 &hwlat_width,
+						 &trace_min_max_fops);
 	if (!hwlat_sample_width)
 		goto err;
 

index 44f46bc1140f..a625bfdb844e 100644
@@ -182,6 +182,15 @@ void trace_hwlat_callback(bool enter)
 		kdata->nmi_count++;
 }
 
+/*
+ * hwlat_err - report a hwlat error.
+ */
+#define hwlat_err(msg) ({							\
+	struct trace_array *tr = hwlat_trace;					\
+										\
+	trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_, msg);	\
+})
+
 /**
  * get_sample - sample the CPU TSC and look for likely hardware latencies
  *

@@ -225,7 +234,7 @@ static int get_sample(void)
 			outer_diff = time_to_us(time_sub(t1, last_t2));
 			/* This shouldn't happen */
 			if (outer_diff < 0) {
-				pr_err(BANNER "time running backwards\n");
+				hwlat_err(BANNER "time running backwards\n");
 				goto out;
 			}
 			if (outer_diff > outer_sample)

@@ -237,7 +246,7 @@ static int get_sample(void)
 
 		/* Check for possible overflows */
 		if (total < last_total) {
-			pr_err("Time total overflowed\n");
+			hwlat_err("Time total overflowed\n");
 			break;
 		}
 		last_total = total;

@@ -253,7 +262,7 @@ static int get_sample(void)
 
 		/* This shouldn't happen */
 		if (diff < 0) {
-			pr_err(BANNER "time running backwards\n");
+			hwlat_err(BANNER "time running backwards\n");
 			goto out;
 		}
 

index 8268bf747d6f..acc17194c160 100644
@@ -358,6 +358,21 @@ TRACE_MAKE_SYSTEM_STR();
 	trace_print_hex_dump_seq(p, prefix_str, prefix_type,		\
 				 rowsize, groupsize, buf, len, ascii)
 
+#undef __print_ns_to_secs
+#define __print_ns_to_secs(value)			\
+	({						\
+		u64 ____val = (u64)(value);		\
+		do_div(____val, NSEC_PER_SEC);		\
+		____val;				\
+	})
+
+#undef __print_ns_without_secs
+#define __print_ns_without_secs(value)			\
+	({						\
+		u64 ____val = (u64)(value);		\
+		(u32) do_div(____val, NSEC_PER_SEC);	\
+	})
+
 #undef DECLARE_EVENT_CLASS
 #define DECLARE_EVENT_CLASS(call, proto, args, tstruct, assign, print)	\
 static notrace enum print_line_t					\

@@ -736,6 +751,16 @@ static inline void ftrace_test_probe_##call(void)			\
 #undef __print_array
 #undef __print_hex_dump
 
+/*
+ * The below is not executed in the kernel. It is only what is
+ * displayed in the print format for userspace to parse.
+ */
+#undef __print_ns_to_secs
+#define __print_ns_to_secs(val) (val) / 1000000000UL
+
+#undef __print_ns_without_secs
+#define __print_ns_without_secs(val) (val) % 1000000000UL
+
 #undef TP_printk
 #define TP_printk(fmt, args...) "\"" fmt "\", "  __stringify(args)
 

index 27bf203ef05a..60492464281e 100644
@@ -1690,8 +1690,7 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt)
 unsigned long __read_mostly	tracing_thresh;
 static const struct file_operations tracing_max_lat_fops;
 
-#if (defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)) && \
-	defined(CONFIG_FSNOTIFY)
+#ifdef LATENCY_FS_NOTIFY
 
 static struct workqueue_struct *fsnotify_wq;
 

index 22f8c652ef8b..87588d1e24ca 100644
@@ -677,13 +677,13 @@ void update_max_tr_single(struct trace_array *tr,
 
 #if (defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)) && \
 	defined(CONFIG_FSNOTIFY)
+#define LATENCY_FS_NOTIFY
+#endif
 
+#ifdef LATENCY_FS_NOTIFY
 void latency_fsnotify(struct trace_array *tr);
-
 #else
-
 static inline void latency_fsnotify(struct trace_array *tr) { }
-
 #endif
 
 #ifdef CONFIG_STACKTRACE

237 lines not on this page · raw message

index 0abd9a1d2852..f6faa31289ba 100644
@@ -7,12 +7,21 @@ extern bool trace_hwlat_callback_enabled;
 extern void trace_hwlat_callback(bool enter);
 #endif
 
+#ifdef CONFIG_OSNOISE_TRACER
+extern bool trace_osnoise_callback_enabled;
+extern void trace_osnoise_callback(bool enter);
+#endif
+
 static inline void ftrace_nmi_enter(void)
 {
 #ifdef CONFIG_HWLAT_TRACER
 	if (trace_hwlat_callback_enabled)
 		trace_hwlat_callback(true);
 #endif
+#ifdef CONFIG_OSNOISE_TRACER
+	if (trace_osnoise_callback_enabled)
+		trace_osnoise_callback(true);
+#endif
 }
 
 static inline void ftrace_nmi_exit(void)

@@ -21,6 +30,10 @@ static inline void ftrace_nmi_exit(void)
 	if (trace_hwlat_callback_enabled)
 		trace_hwlat_callback(false);
 #endif
+#ifdef CONFIG_OSNOISE_TRACER
+	if (trace_osnoise_callback_enabled)
+		trace_osnoise_callback(false);
+#endif
 }
 
 #endif /* _LINUX_FTRACE_IRQ_H */

index be1e130ed87c..4e3858640c47 100644
@@ -41,6 +41,11 @@ int trace_array_init_printk(struct trace_array *tr);
 void trace_array_put(struct trace_array *tr);
 struct trace_array *trace_array_get_by_name(const char *name);
 int trace_array_destroy(struct trace_array *tr);
+
+/* For osnoise tracer */
+int osnoise_arch_register(void);
+void osnoise_arch_unregister(void);
+
 #endif	/* CONFIG_TRACING */
 
 #endif	/* _LINUX_TRACE_H */

142 lines not on this page · raw message

index 87588d1e24ca..b959c9ec9711 100644
@@ -44,6 +44,7 @@ enum trace_type {
 	TRACE_BLK,
 	TRACE_BPUTS,
 	TRACE_HWLAT,
+	TRACE_OSNOISE,
 	TRACE_RAW_DATA,
 	TRACE_FUNC_REPEATS,
 

@@ -297,7 +298,8 @@ struct trace_array {
 	struct array_buffer	max_buffer;
 	bool			allocated_snapshot;
 #endif
-#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)
+#if defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) \
+	|| defined(CONFIG_OSNOISE_TRACER)
 	unsigned long		max_latency;
 #ifdef CONFIG_FSNOTIFY
 	struct dentry		*d_max_latency;

@@ -445,6 +447,7 @@ extern void __ftrace_bad_type(void);
 		IF_ASSIGN(var, ent, struct bprint_entry, TRACE_BPRINT);	\
 		IF_ASSIGN(var, ent, struct bputs_entry, TRACE_BPUTS);	\
 		IF_ASSIGN(var, ent, struct hwlat_entry, TRACE_HWLAT);	\
+		IF_ASSIGN(var, ent, struct osnoise_entry, TRACE_OSNOISE);\
 		IF_ASSIGN(var, ent, struct raw_data_entry, TRACE_RAW_DATA);\
 		IF_ASSIGN(var, ent, struct trace_mmiotrace_rw,		\
 			  TRACE_MMIO_RW);				\

@@ -675,8 +678,8 @@ void update_max_tr_single(struct trace_array *tr,
 			  struct task_struct *tsk, int cpu);
 #endif /* CONFIG_TRACER_MAX_TRACE */
 
-#if (defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER)) && \
-	defined(CONFIG_FSNOTIFY)
+#if (defined(CONFIG_TRACER_MAX_TRACE) || defined(CONFIG_HWLAT_TRACER) \
+	|| defined(CONFIG_OSNOISE_TRACER)) && defined(CONFIG_FSNOTIFY)
 #define LATENCY_FS_NOTIFY
 #endif
 

index 251c819cf0c5..158c0984b59b 100644
@@ -360,3 +360,28 @@ FTRACE_ENTRY(func_repeats, func_repeats_entry,
 		 __entry->count,
 		 FUNC_REPEATS_GET_DELTA_TS(__entry))
 );
+
+FTRACE_ENTRY(osnoise, osnoise_entry,
+
+	TRACE_OSNOISE,
+
+	F_STRUCT(
+		__field(	u64,			noise		)
+		__field(	u64,			runtime		)
+		__field(	u64,			max_sample	)
+		__field(	unsigned int,		hw_count	)
+		__field(	unsigned int,		nmi_count	)
+		__field(	unsigned int,		irq_count	)
+		__field(	unsigned int,		softirq_count	)
+		__field(	unsigned int,		thread_count	)
+	),
+
+	F_printk("noise:%llu\tmax_sample:%llu\thw:%u\tnmi:%u\tirq:%u\tsoftirq:%u\tthread:%u\n",
+		 __entry->noise,
+		 __entry->max_sample,
+		 __entry->hw_count,
+		 __entry->nmi_count,
+		 __entry->irq_count,
+		 __entry->softirq_count,
+		 __entry->thread_count)
+);

1,384 lines not on this page · raw message

90 lines not on this page · raw message

index b959c9ec9711..d83bbb6859b4 100644
@@ -45,6 +45,7 @@ enum trace_type {
 	TRACE_BPUTS,
 	TRACE_HWLAT,
 	TRACE_OSNOISE,
+	TRACE_TIMERLAT,
 	TRACE_RAW_DATA,
 	TRACE_FUNC_REPEATS,
 

@@ -448,6 +449,7 @@ extern void __ftrace_bad_type(void);
 		IF_ASSIGN(var, ent, struct bputs_entry, TRACE_BPUTS);	\
 		IF_ASSIGN(var, ent, struct hwlat_entry, TRACE_HWLAT);	\
 		IF_ASSIGN(var, ent, struct osnoise_entry, TRACE_OSNOISE);\
+		IF_ASSIGN(var, ent, struct timerlat_entry, TRACE_TIMERLAT);\
 		IF_ASSIGN(var, ent, struct raw_data_entry, TRACE_RAW_DATA);\
 		IF_ASSIGN(var, ent, struct trace_mmiotrace_rw,		\
 			  TRACE_MMIO_RW);				\

index 158c0984b59b..cd41e863b51c 100644
@@ -385,3 +385,19 @@ FTRACE_ENTRY(osnoise, osnoise_entry,
 		 __entry->softirq_count,
 		 __entry->thread_count)
 );
+
+FTRACE_ENTRY(timerlat, timerlat_entry,
+
+	TRACE_TIMERLAT,
+
+	F_STRUCT(
+		__field(	unsigned int,		seqnum		)
+		__field(	int,			context		)
+		__field(	u64,			timer_latency	)
+	),
+
+	F_printk("seq:%u\tcontext:%d\ttimer_latency:%llu\n",
+		 __entry->seqnum,
+		 __entry->context,
+		 __entry->timer_latency)
+);

810 lines not on this page · raw message

59 lines not on this page · raw message

index a625bfdb844e..20e31f79ebd9 100644
@@ -396,13 +396,19 @@ static int kthread_fn(void *data)
 static void stop_single_kthread(void)
 {
 	struct hwlat_kthread_data *kdata = get_cpu_data();
-	struct task_struct *kthread = kdata->kthread;
+	struct task_struct *kthread;
+
+	get_online_cpus();
+	kthread = kdata->kthread;
 
 	if (!kthread)
-		return;
+		goto out_put_cpus;
 
 	kthread_stop(kthread);
 	kdata->kthread = NULL;
+
+out_put_cpus:
+	put_online_cpus();
 }
 
 

@@ -419,20 +425,19 @@ static int start_single_kthread(struct trace_array *tr)
 	struct task_struct *kthread;
 	int next_cpu;
 
+	get_online_cpus();
 	if (kdata->kthread)
-		return 0;
+		goto out_put_cpus;
 
 	kthread = kthread_create(kthread_fn, NULL, "hwlatd");
 	if (IS_ERR(kthread)) {
 		pr_err(BANNER "could not start sampling thread\n");
+		put_online_cpus();
 		return -ENOMEM;
 	}
 
-
 	/* Just pick the first CPU on first iteration */
-	get_online_cpus();
 	cpumask_and(current_mask, cpu_online_mask, tr->tracing_cpumask);
-	put_online_cpus();
 
 	if (hwlat_data.thread_mode == MODE_ROUND_ROBIN) {
 		next_cpu = cpumask_first(current_mask);

@@ -446,6 +451,8 @@ static int start_single_kthread(struct trace_array *tr)
 	kdata->kthread = kthread;
 	wake_up_process(kthread);
 
+out_put_cpus:
+	put_online_cpus();
 	return 0;
 }
 

index 20e31f79ebd9..a6c0cdaf4b87 100644
@@ -466,6 +466,7 @@ static void stop_cpu_kthread(unsigned int cpu)
 	kthread = per_cpu(hwlat_per_cpu_data, cpu).kthread;
 	if (kthread)
 		kthread_stop(kthread);
+	per_cpu(hwlat_per_cpu_data, cpu).kthread = NULL;
 }
 
 /*

@@ -506,6 +507,68 @@ static int start_cpu_kthread(unsigned int cpu)
 	return 0;
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static void hwlat_hotplug_workfn(struct work_struct *dummy)
+{
+	struct trace_array *tr = hwlat_trace;
+	unsigned int cpu = smp_processor_id();
+
+	mutex_lock(&trace_types_lock);
+	mutex_lock(&hwlat_data.lock);
+	get_online_cpus();
+
+	if (!hwlat_busy || hwlat_data.thread_mode != MODE_PER_CPU)
+		goto out_unlock;
+
+	if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))
+		goto out_unlock;
+
+	start_cpu_kthread(cpu);
+
+out_unlock:
+	put_online_cpus();
+	mutex_unlock(&hwlat_data.lock);
+	mutex_unlock(&trace_types_lock);
+}
+
+static DECLARE_WORK(hwlat_hotplug_work, hwlat_hotplug_workfn);
+
+/*
+ * hwlat_cpu_init - CPU hotplug online callback function
+ */
+static int hwlat_cpu_init(unsigned int cpu)
+{
+	schedule_work_on(cpu, &hwlat_hotplug_work);
+	return 0;
+}
+
+/*
+ * hwlat_cpu_die - CPU hotplug offline callback function
+ */
+static int hwlat_cpu_die(unsigned int cpu)
+{
+	stop_cpu_kthread(cpu);
+	return 0;
+}
+
+static void hwlat_init_hotplug_support(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "trace/hwlat:online",
+				hwlat_cpu_init, hwlat_cpu_die);
+	if (ret < 0)
+		pr_warn(BANNER "Error to init cpu hotplug support\n");
+
+	return;
+}
+#else /* CONFIG_HOTPLUG_CPU */
+static void hwlat_init_hotplug_support(void)
+{
+	return;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
 /*
  * start_per_cpu_kthreads - Kick off the hardware latency sampling/detector kthreads
  *

@@ -822,6 +885,8 @@ __init static int init_hwlat_tracer(void)
 	if (ret)
 		return ret;
 
+	hwlat_init_hotplug_support();
+
 	init_tracefs();
 
 	return 0;

index 8546e66bafcb..38aa5e208ffd 100644
@@ -1416,22 +1416,67 @@ static int timerlat_main(void *data)
 #endif /* CONFIG_TIMERLAT_TRACER */
 
 /*
- * stop_per_cpu_kthread - stop per-cpu threads
+ * stop_kthread - stop a workload thread
+ */
+static void stop_kthread(unsigned int cpu)
+{
+	struct task_struct *kthread;
+
+	kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
+	if (kthread)
+		kthread_stop(kthread);
+	per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+}
+
+/*
+ * stop_per_cpu_kthread - Stop per-cpu threads
  *
  * Stop the osnoise sampling htread. Use this on unload and at system
  * shutdown.
  */
 static void stop_per_cpu_kthreads(void)
 {
-	struct task_struct *kthread;
 	int cpu;
 
-	for_each_online_cpu(cpu) {
-		kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
-		if (kthread)
-			kthread_stop(kthread);
-		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
+	get_online_cpus();
+
+	for_each_online_cpu(cpu)
+		stop_kthread(cpu);
+
+	put_online_cpus();
+}
+
+/*
+ * start_kthread - Start a workload tread
+ */
+static int start_kthread(unsigned int cpu)
+{
+	struct task_struct *kthread;
+	void *main = osnoise_main;
+	char comm[24];
+
+#ifdef CONFIG_TIMERLAT_TRACER
+	if (osnoise_data.timerlat_tracer) {
+		snprintf(comm, 24, "timerlat/%d", cpu);
+		main = timerlat_main;
+	} else {
+		snprintf(comm, 24, "osnoise/%d", cpu);
 	}
+#else
+	snprintf(comm, 24, "osnoise/%d", cpu);
+#endif
+	kthread = kthread_create_on_cpu(main, NULL, cpu, comm);
+
+	if (IS_ERR(kthread)) {
+		pr_err(BANNER "could not start sampling thread\n");
+		stop_per_cpu_kthreads();
+		return -ENOMEM;
+	}
+
+	per_cpu(per_cpu_osnoise_var, cpu).kthread = kthread;
+	wake_up_process(kthread);
+
+	return 0;
 }
 
 /*

@@ -1443,9 +1488,7 @@ static void stop_per_cpu_kthreads(void)
 static int start_per_cpu_kthreads(struct trace_array *tr)
 {
 	struct cpumask *current_mask = &save_cpumask;
-	struct task_struct *kthread;
-	char comm[24];
-	void *main = osnoise_main;
+	int retval;
 	int cpu;
 
 	get_online_cpus();

@@ -1457,37 +1500,91 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
 	 * And the CPU is online.
 	 */
 	cpumask_and(current_mask, cpu_online_mask, current_mask);
-	put_online_cpus();
 
-	for_each_online_cpu(cpu)
+	for_each_possible_cpu(cpu)
 		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
 
 	for_each_cpu(cpu, current_mask) {
-#ifdef CONFIG_TIMERLAT_TRACER
-		if (osnoise_data.timerlat_tracer) {
-			snprintf(comm, 24, "timerlat/%d", cpu);
-			main = timerlat_main;
-		} else {
-			snprintf(comm, 24, "osnoise/%d", cpu);
-		}
-#else
-		snprintf(comm, 24, "osnoise/%d", cpu);
-#endif
-		kthread = kthread_create_on_cpu(main, NULL, cpu, comm);
-
-		if (IS_ERR(kthread)) {
-			pr_err(BANNER "could not start sampling thread\n");
+		retval = start_kthread(cpu);
+		if (retval) {
 			stop_per_cpu_kthreads();
-			return -ENOMEM;
+			return retval;
 		}
-
-		per_cpu(per_cpu_osnoise_var, cpu).kthread = kthread;
-		wake_up_process(kthread);
 	}
 
+	put_online_cpus();
+
 	return 0;
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static void osnoise_hotplug_workfn(struct work_struct *dummy)
+{
+	struct trace_array *tr = osnoise_trace;
+	unsigned int cpu = smp_processor_id();
+
+
+	mutex_lock(&trace_types_lock);
+
+	if (!osnoise_busy)
+		goto out_unlock_trace;
+
+	mutex_lock(&interface_lock);
+	get_online_cpus();
+
+	if (!cpumask_test_cpu(cpu, &osnoise_cpumask))
+		goto out_unlock;
+
+	if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))
+		goto out_unlock;
+
+	start_kthread(cpu);
+
+out_unlock:
+	put_online_cpus();
+	mutex_unlock(&interface_lock);
+out_unlock_trace:
+	mutex_unlock(&trace_types_lock);
+}
+
+static DECLARE_WORK(osnoise_hotplug_work, osnoise_hotplug_workfn);
+
+/*
+ * osnoise_cpu_init - CPU hotplug online callback function
+ */
+static int osnoise_cpu_init(unsigned int cpu)
+{
+	schedule_work_on(cpu, &osnoise_hotplug_work);
+	return 0;
+}
+
+/*
+ * osnoise_cpu_die - CPU hotplug offline callback function
+ */
+static int osnoise_cpu_die(unsigned int cpu)
+{
+	stop_kthread(cpu);
+	return 0;
+}
+
+static void osnoise_init_hotplug_support(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "trace/osnoise:online",
+				osnoise_cpu_init, osnoise_cpu_die);
+	if (ret < 0)
+		pr_warn(BANNER "Error to init cpu hotplug support\n");
+
+	return;
+}
+#else /* CONFIG_HOTPLUG_CPU */
+static void osnoise_init_hotplug_support(void)
+{
+	return 0;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
 /*
  * osnoise_cpus_read - Read function for reading the "cpus" file
  * @filp: The active open file structure

@@ -1583,7 +1680,14 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
 		osnoise_tracer_stop(tr);
 
 	mutex_lock(&interface_lock);
+	/*
+	 * osnoise_cpumask is read by CPU hotplug operations.
+	 */
+	get_online_cpus();
+
 	cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new);
+
+	put_online_cpus();
 	mutex_unlock(&interface_lock);
 
 	if (running)

@@ -1940,6 +2044,7 @@ __init static int init_osnoise_tracer(void)
 		return ret;
 	}
 #endif
+	osnoise_init_hotplug_support();
 
 	init_tracefs();