Move the PCPU_MD_FIELDS last in struct pcpu. While this header is

private to the kernel, some ports define _KERNEL and include this
header. While arguably this is wrong, it's also reality. By having
the MD fields last, architectures that have CPU-specific variations
of PCPU_MD_FIELDS will at least have the MI fields at a constant
offset.  Of course, having all MI fields first helps kernel debugging
as well, so this is not a change without some benefits to us.

This change does not result in an ABI breakage, because this header
is not part of the ABI. Recompilation of lsof is required though :-)

1 files changed, 11 insertions, 1 deletions

diff --git a/sys/sys/pcpu.h b/sys/sys/pcpu.h
index a129997..df73985 100644
--- a/sys/sys/pcpu.h
+++ b/sys/sys/pcpu.h
@@ -81,7 +81,6 @@ struct pcpu {
 	int		pc_ktr_idx;		/* Index into trace table */
 	char		*pc_ktr_buf;
 #endif
-	PCPU_MD_FIELDS;
 	struct vmmeter	pc_cnt;			/* VM stats counters */
 	long		pc_cp_time[CPUSTATES];	/* statclock ticks */
 	struct device	*pc_device;
@@ -94,6 +93,17 @@ struct pcpu {
 	 */
 	struct rm_queue  pc_rm_queue; 
 
+	/*
+	 * Keep MD fields last, so that CPU-specific variations on a
+	 * single architecture don't result in offset variations of
+	 * the machine-independent fields of the pcpu. Even though
+	 * the pcpu structure is private to the kernel, some ports
+	 * (e.g. lsof, part of gtop) define _KERNEL and include this
+	 * header. While strictly speaking this is wrong, there's no
+	 * reason not to keep the offsets of the MI fields contants.
+	 * If only to make kernel debugging easier...
+	 */
+	PCPU_MD_FIELDS;
 };
 
 SLIST_HEAD(cpuhead, pcpu);