svn commit: r242200 - in stable/8/sys: conf kern

[Davide Italiano]

Author: davide
Date: Sat Oct 27 23:34:18 2012
New Revision: 242200
URL: http://svn.freebsd.org/changeset/base/242200

Log:
  MFC r238925:
  Until now KTR_ENTRIES, which defines the size of circular buffer used in
  ktr(4), was constrained to be a power of two. Remove this constraint and
  update sys/conf/NOTES accordingly.

Modified:
  stable/8/sys/conf/NOTES
  stable/8/sys/kern/kern_ktr.c
Directory Properties:
  stable/8/sys/   (props changed)
  stable/8/sys/conf/   (props changed)
  stable/8/sys/kern/   (props changed)

Modified: stable/8/sys/conf/NOTES
==============================================================================
--- stable/8/sys/conf/NOTES	Sat Oct 27 23:30:46 2012	(r242199)
+++ stable/8/sys/conf/NOTES	Sat Oct 27 23:34:18 2012	(r242200)
@@ -409,7 +409,7 @@ options 	KTRACE_REQUEST_POOL=101
 # KTR is a kernel tracing mechanism imported from BSD/OS.  Currently
 # it has no userland interface aside from a few sysctl's.  It is
 # enabled with the KTR option.  KTR_ENTRIES defines the number of
-# entries in the circular trace buffer; it must be a power of two.
+# entries in the circular trace buffer; it may be an arbitrary number.
 # KTR_COMPILE defines the mask of events to compile into the kernel as
 # defined by the KTR_* constants in <sys/ktr.h>.  KTR_MASK defines the
 # initial value of the ktr_mask variable which determines at runtime

Modified: stable/8/sys/kern/kern_ktr.c
==============================================================================
--- stable/8/sys/kern/kern_ktr.c	Sat Oct 27 23:30:46 2012	(r242199)
+++ stable/8/sys/kern/kern_ktr.c	Sat Oct 27 23:34:18 2012	(r242200)
@@ -235,7 +235,7 @@ ktr_tracepoint(u_int mask, const char *f
 	{
 		do {
 			saveindex = ktr_idx;
-			newindex = (saveindex + 1) & (KTR_ENTRIES - 1);
+			newindex = (saveindex + 1) % KTR_ENTRIES;
 		} while (atomic_cmpset_rel_int(&ktr_idx, saveindex, newindex) == 0);
 		entry = &ktr_buf[saveindex];
 	}
@@ -290,7 +290,7 @@ static	int db_mach_vtrace(void);
 DB_SHOW_COMMAND(ktr, db_ktr_all)
 {
 	
-	tstate.cur = (ktr_idx - 1) & (KTR_ENTRIES - 1);
+	tstate.cur = (ktr_idx - 1) % KTR_ENTRIES;
 	tstate.first = -1;
 	db_ktr_verbose = 0;
 	db_ktr_verbose |= (index(modif, 'v') != NULL) ? 2 : 0;