freebsd-dev/module/zfs/zfs_debug.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
 */

#include <sys/zfs_context.h>

list_t zfs_dbgmsgs;
int zfs_dbgmsg_size;
kmutex_t zfs_dbgmsgs_lock;
int zfs_dbgmsg_maxsize = 4<<20; /* 4MB */

void
zfs_dbgmsg_init(void)
{
	list_create(&zfs_dbgmsgs, sizeof (zfs_dbgmsg_t),
	    offsetof(zfs_dbgmsg_t, zdm_node));
	mutex_init(&zfs_dbgmsgs_lock, NULL, MUTEX_DEFAULT, NULL);
}

void
zfs_dbgmsg_fini(void)
{
	zfs_dbgmsg_t *zdm;

	while ((zdm = list_remove_head(&zfs_dbgmsgs)) != NULL) {
		int size = sizeof (zfs_dbgmsg_t) + strlen(zdm->zdm_msg);
		kmem_free(zdm, size);
		zfs_dbgmsg_size -= size;
	}
	mutex_destroy(&zfs_dbgmsgs_lock);
	ASSERT0(zfs_dbgmsg_size);
}

/*
 * To get this data enable the zfs__dbgmsg tracepoint as shown:
 *
 * # Enable zfs__dbgmsg tracepoint, clear the tracepoint ring buffer
 * $ echo 1 > /sys/kernel/debug/tracing/events/zfs/enable
 * $ echo 0 > /sys/kernel/debug/tracing/trace
 *
 * # Dump the ring buffer.
 * $ cat /sys/kernel/debug/tracing/trace
 */
void
zfs_dbgmsg(const char *fmt, ...)
{
	int size;
	va_list adx;
	char *nl;
	zfs_dbgmsg_t *zdm;

	va_start(adx, fmt);
	size = vsnprintf(NULL, 0, fmt, adx);
	va_end(adx);

	/*
	 * There is one byte of string in sizeof (zfs_dbgmsg_t), used
	 * for the terminating null.
	 */
	zdm = kmem_alloc(sizeof (zfs_dbgmsg_t) + size, KM_SLEEP);
	zdm->zdm_timestamp = gethrestime_sec();

	va_start(adx, fmt);
	(void) vsnprintf(zdm->zdm_msg, size + 1, fmt, adx);
	va_end(adx);

	/*
	 * Get rid of trailing newline.
	 */
	nl = strrchr(zdm->zdm_msg, '\n');
	if (nl != NULL)
		*nl = '\0';

	DTRACE_PROBE1(zfs__dbgmsg, char *, zdm->zdm_msg);

	mutex_enter(&zfs_dbgmsgs_lock);
	list_insert_tail(&zfs_dbgmsgs, zdm);
	zfs_dbgmsg_size += sizeof (zfs_dbgmsg_t) + size;
	while (zfs_dbgmsg_size > zfs_dbgmsg_maxsize) {
		zdm = list_remove_head(&zfs_dbgmsgs);
		size = sizeof (zfs_dbgmsg_t) + strlen(zdm->zdm_msg);
		kmem_free(zdm, size);
		zfs_dbgmsg_size -= size;
	}
	mutex_exit(&zfs_dbgmsgs_lock);
}

void
zfs_dbgmsg_print(const char *tag)
{
#if !defined(_KERNEL)
	zfs_dbgmsg_t *zdm;

	(void) printf("ZFS_DBGMSG(%s):\n", tag);
	mutex_enter(&zfs_dbgmsgs_lock);
	for (zdm = list_head(&zfs_dbgmsgs); zdm;
	    zdm = list_next(&zfs_dbgmsgs, zdm))
		(void) printf("%s\n", zdm->zdm_msg);
	mutex_exit(&zfs_dbgmsgs_lock);
#endif /* !_KERNEL */
}