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Commit c68ba4a7 authored by Peter Oberparleiter's avatar Peter Oberparleiter Committed by Greg Kroah-Hartman
Browse files

s390/debug: fix debug area life cycle 



[ Upstream commit 9372a82892c2caa6bccab9a4081166fa769699f8 ]

Currently allocation and registration of s390dbf debug areas are tied
together. As a result, a debug area cannot be unregistered and
re-registered while any process has an associated debugfs file open.

Fix this by splitting alloc/release from register/unregister.

Signed-off-by: default avatarPeter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 7a67a00e

arch/s390/kernel/debug.c

+56 −46
Original line number Diff line number Diff line
@@ -327,24 +327,6 @@ static debug_info_t *debug_info_create(const char *name, int pages_per_area, 
		goto out;



	rc->mode = mode & ~S_IFMT;



	/* create root directory */

	rc->debugfs_root_entry = debugfs_create_dir(rc->name,

						    debug_debugfs_root_entry);



	/* append new element to linked list */

	if (!debug_area_first) {

		/* first element in list */

		debug_area_first = rc;

		rc->prev = NULL;

	} else {

		/* append element to end of list */

		debug_area_last->next = rc;

		rc->prev = debug_area_last;

	}

	debug_area_last = rc;

	rc->next = NULL;



	refcount_set(&rc->ref_count, 1);

out:

	return rc;
@@ -404,28 +386,11 @@ static void debug_info_get(debug_info_t *db_info) 
 */

static void debug_info_put(debug_info_t *db_info)

{

	int i;



	if (!db_info)

		return;

	if (refcount_dec_and_test(&db_info->ref_count)) {

		for (i = 0; i < DEBUG_MAX_VIEWS; i++) {

			if (!db_info->views[i])

				continue;

			debugfs_remove(db_info->debugfs_entries[i]);

		}

		debugfs_remove(db_info->debugfs_root_entry);

		if (db_info == debug_area_first)

			debug_area_first = db_info->next;

		if (db_info == debug_area_last)

			debug_area_last = db_info->prev;

		if (db_info->prev)

			db_info->prev->next = db_info->next;

		if (db_info->next)

			db_info->next->prev = db_info->prev;

	if (refcount_dec_and_test(&db_info->ref_count))

		debug_info_free(db_info);

}

}



/*

 * debug_format_entry:
@@ -648,6 +613,31 @@ static int debug_close(struct inode *inode, struct file *file) 
	return 0; /* success */

}



/* Create debugfs entries and add to internal list. */

static void _debug_register(debug_info_t *id)

{

	/* create root directory */

	id->debugfs_root_entry = debugfs_create_dir(id->name,

						    debug_debugfs_root_entry);



	/* append new element to linked list */

	if (!debug_area_first) {

		/* first element in list */

		debug_area_first = id;

		id->prev = NULL;

	} else {

		/* append element to end of list */

		debug_area_last->next = id;

		id->prev = debug_area_last;

	}

	debug_area_last = id;

	id->next = NULL;



	debug_register_view(id, &debug_level_view);

	debug_register_view(id, &debug_flush_view);

	debug_register_view(id, &debug_pages_view);

}



/**

 * debug_register_mode() - creates and initializes debug area.

 *
@@ -677,19 +667,16 @@ debug_info_t *debug_register_mode(const char *name, int pages_per_area, 
	if ((uid != 0) || (gid != 0))

		pr_warn("Root becomes the owner of all s390dbf files in sysfs\n");

	BUG_ON(!initialized);

	mutex_lock(&debug_mutex);



	/* create new debug_info */

	rc = debug_info_create(name, pages_per_area, nr_areas, buf_size, mode);

	if (!rc)

		goto out;

	debug_register_view(rc, &debug_level_view);

	debug_register_view(rc, &debug_flush_view);

	debug_register_view(rc, &debug_pages_view);

out:

	if (!rc)

		pr_err("Registering debug feature %s failed\n", name);

	if (rc) {

		mutex_lock(&debug_mutex);

		_debug_register(rc);

		mutex_unlock(&debug_mutex);

	} else {

		pr_err("Registering debug feature %s failed\n", name);

	}

	return rc;

}

EXPORT_SYMBOL(debug_register_mode);
@@ -718,6 +705,27 @@ debug_info_t *debug_register(const char *name, int pages_per_area, 
}

EXPORT_SYMBOL(debug_register);



/* Remove debugfs entries and remove from internal list. */

static void _debug_unregister(debug_info_t *id)

{

	int i;



	for (i = 0; i < DEBUG_MAX_VIEWS; i++) {

		if (!id->views[i])

			continue;

		debugfs_remove(id->debugfs_entries[i]);

	}

	debugfs_remove(id->debugfs_root_entry);

	if (id == debug_area_first)

		debug_area_first = id->next;

	if (id == debug_area_last)

		debug_area_last = id->prev;

	if (id->prev)

		id->prev->next = id->next;

	if (id->next)

		id->next->prev = id->prev;

}



/**

 * debug_unregister() - give back debug area.

 *
@@ -731,8 +739,10 @@ void debug_unregister(debug_info_t *id) 
	if (!id)

		return;

	mutex_lock(&debug_mutex);

	debug_info_put(id);

	_debug_unregister(id);

	mutex_unlock(&debug_mutex);



	debug_info_put(id);

}

EXPORT_SYMBOL(debug_unregister);