usched questions and a patch

[Michal Belczyk <belczyk@xxxxxxxxxxxxx>]

Hello hackers!

I've got a question about the TAILQ_ENTRY(lwp) lwp_procq in struct lwp - why
isn't it a part of lwp_usdata union?  Isn't it a usched-dependent data?  What
if a different usched wants to hold its lwps in e.g. red-black tree or a
heap?

Another thing I noticed is that usched_set() syscall does not zero the
content of lwp_usdata which makes impossible for the newly selected usched
to distinguish between an lwp it already had on its queue/tree/whatever and
had already put some data into its lwp_usdata, and a 'new' lwp it will get in
the following call to acquire_curproc() from userexit() IIRC.

What do You think about the attached patch?

And one more thing - what do You think about adding another usched API call,
e.g.  exiting_curproc() called from exit1() instead of release_curproc() so
that a usched could (1) actually trace lwps during their lifetime and
(2) differentiate between lwps 'only' going into kernel and the ones that do
exit1()?


-- 
Michal Belczyk

Index: bin/ps/keyword.c
===================================================================
RCS file: /home/dcvs/src/bin/ps/keyword.c,v
retrieving revision 1.21
diff -u -r1.21 keyword.c
--- bin/ps/keyword.c	11 Oct 2005 22:10:22 -0000	1.21
+++ bin/ps/keyword.c	20 Dec 2005 19:02:34 -0000
@@ -153,8 +153,6 @@
 	{"re", "RE", NULL, 0, pvar, NULL, 3, POFF(p_swtime), UINT, "d", NULL},
 	{"rgid", "RGID", NULL, 0, evar, NULL, UIDLEN, EOFF(e_ucred.cr_rgid),
 		UINT, UIDFMT, NULL},
-	{"rlink", "RLINK", NULL, 0, pvar, NULL, 8, POFF(p_lwp.lwp_procq.tqe_prev), KPTR, "lx",
-		NULL},
 	{"rss", "RSS", NULL, 0, p_rssize, NULL, 4, 0, 0, NULL, NULL},
 	{"rssize", "", "rsz", 0, NULL, NULL, 0, 0, 0, NULL, NULL},
 	{"rsz", "RSZ", NULL, 0, rssize, NULL, 4, 0, 0, NULL, NULL},
Index: bin/ps/ps.1
===================================================================
RCS file: /home/dcvs/src/bin/ps/ps.1,v
retrieving revision 1.7
diff -u -r1.7 ps.1
--- bin/ps/ps.1	14 Nov 2005 18:49:48 -0000	1.7
+++ bin/ps/ps.1	20 Dec 2005 19:03:29 -0000
@@ -424,8 +424,6 @@
 .It rgid
 real group
 .Tn ID
-.It rlink
-reverse link on run queue, or 0
 .It rss
 resident set size
 .It rsz
Index: sys/kern/kern_usched.c
===================================================================
RCS file: /home/dcvs/src/sys/kern/kern_usched.c,v
retrieving revision 1.1
diff -u -r1.1 kern_usched.c
--- sys/kern/kern_usched.c	16 Nov 2005 02:24:30 -0000	1.1
+++ sys/kern/kern_usched.c	20 Dec 2005 19:42:18 -0000
@@ -161,6 +161,11 @@
 	if (item && item != p->p_usched) {
 		p->p_usched->release_curproc(&p->p_lwp);
 		p->p_usched = item;
+		/*
+		 * Give the new usched a chance to recognize the lwp
+		 * as a 'new' one.
+		 */
+		bzero(&p->p_lwp.lwp_usdata, sizeof(p->p_lwp.lwp_usdata));
 	} else if (item == NULL) {
 		error = EINVAL;
 	}
Index: sys/kern/usched_bsd4.c
===================================================================
RCS file: /home/dcvs/src/sys/kern/usched_bsd4.c,v
retrieving revision 1.6
diff -u -r1.6 usched_bsd4.c
--- sys/kern/usched_bsd4.c	21 Nov 2005 21:59:50 -0000	1.6
+++ sys/kern/usched_bsd4.c	20 Dec 2005 18:59:29 -0000
@@ -81,6 +81,7 @@
 #define lwp_rqindex	lwp_usdata.bsd4.rqindex
 #define lwp_origcpu	lwp_usdata.bsd4.origcpu
 #define lwp_estcpu	lwp_usdata.bsd4.estcpu
+#define lwp_procq	lwp_usdata.bsd4.lwp_procq
 
 static void bsd4_acquire_curproc(struct lwp *lp);
 static void bsd4_release_curproc(struct lwp *lp);
Index: sys/sys/proc.h
===================================================================
RCS file: /home/dcvs/src/sys/sys/proc.h,v
retrieving revision 1.73
diff -u -r1.73 proc.h
--- sys/sys/proc.h	1 Dec 2005 18:30:10 -0000	1.73
+++ sys/sys/proc.h	20 Dec 2005 18:58:21 -0000
@@ -132,7 +132,6 @@
 struct jail;
 
 struct lwp {
-	TAILQ_ENTRY(lwp) lwp_procq;	/* run/sleep queue. */
 	LIST_ENTRY(lwp) lwp_list;	/* List of all threads in the proc. */
 
 	struct proc	*lwp_proc;	/* Link to our proc. */
Index: sys/sys/usched.h
===================================================================
RCS file: /home/dcvs/src/sys/sys/usched.h,v
retrieving revision 1.7
diff -u -r1.7 usched.h
--- sys/sys/usched.h	16 Nov 2005 02:24:33 -0000	1.7
+++ sys/sys/usched.h	20 Dec 2005 18:58:18 -0000
@@ -42,6 +42,7 @@
      * BSD4 scheduler. 
      */
     struct {
+	TAILQ_ENTRY(lwp) lwp_procq;	/* run/sleep queue. */
 	short	priority;	/* lower is better */
 	char	interactive;	/* (currently not used) */
 	char	rqindex;
@@ -49,7 +50,7 @@
 	int	estcpu;		/* dynamic priority modification */
     } bsd4;
 
-    int		pad[4];		/* PAD for future expansion */
+    int		pad[8];		/* PAD for future expansion */
 };
 
 /*