From 03d5e49ae91c6a972c68d38622c2b4654fe0983f Mon Sep 17 00:00:00 2001
From: Phil Budne <phil@ultimate.com>
Date: Tue, 8 Mar 2016 11:49:18 -0500
Subject: [PATCH] sys comments for rmes/smes calls, process table (user list)
 words noticed "exit" call falls into "rmes" call!!!

---
 src/sys/s1.s | 10 ++++-----
 src/sys/s2.s |  2 +-
 src/sys/s3.s | 63 ++++++++++++++++++++++++++++++----------------------
 src/sys/s7.s |  2 +-
 src/sys/s8.s |  7 ++++--
 5 files changed, 48 insertions(+), 36 deletions(-)

diff --git a/src/sys/s1.s b/src/sys/s1.s
index f50088c..6b71282 100644
--- a/src/sys/s1.s
+++ b/src/sys/s1.s
@@ -86,7 +86,7 @@ swap: 0
    jms lookfor; 1 " in/ready
       skp
    jmp 1b			" loop until a process becomes ready
-   dzm maxquant			" here with in/ready (self?)
+   dzm maxquant			" in/ready (self?): come back next tick!
    jmp 3f
 1:				" here with out/ready process
    dac 9f+t			" save process pointer (swapped out) in t0
@@ -97,7 +97,7 @@ swap: 0
    jmp 2f
 1:
    lac swap
-   dac u.swapret		" return to scheduler when swapped back
+   dac u.swapret		" return to caller when swapped back
    iof
    lac o200000			" change status to swapped out
    tad u.ulistp i
@@ -105,13 +105,13 @@ swap: 0
    ion
    jms dskswap; 07000		" swap process out
    lac u.dspbuf
-   sna
-   jmp 2f
+   sna				" process using display??
+   jmp 2f			"  no
    law dspbuf
    jms movdsp
 2:
    iof				" disable interrupts
-   lac o600000			" change status (1->7?)
+   lac o600000			" change status (1->7?????)
    tad 9f+t i
    dac 9f+t i
    ion				" enable interrupts
diff --git a/src/sys/s2.s b/src/sys/s2.s
index 4006ed5..64d6f93 100644
--- a/src/sys/s2.s
+++ b/src/sys/s2.s
@@ -284,7 +284,7 @@ open1:				" common exit for open/creat
    jmp 1f			"  no
    iof				" yes: disable interrupts
    lac ii			" get i number
-   tad swr			" get read routine table addr
+   tad swr			" add to base instruction
    dac .+1
    jmp .. i			" dispatch to read routine
 1:
diff --git a/src/sys/s3.s b/src/sys/s3.s
index 45be20e..baec05c 100644
--- a/src/sys/s3.s
+++ b/src/sys/s3.s
@@ -1,7 +1,7 @@
 "** 01-s1.pdf page 14
 " s3
 
-	" search for user (process)
+	" search for user (process) table entry
 	" call:
 	"   jms searchu; worker_routine_addr
 	" worker called with copy of a process table entry in "lu"
@@ -113,36 +113,44 @@ badcal:				" bad (unimplemented) system call
    isz u.ulistp
    dzm u.ulistp i		" clear pid in process table
    jms swap			" find a new process to run
+	" exit falls into "rmes" !!!
 
+	" rmes system call
+	"   sys smes
+	" returns with message delivered, or error if process does not exit
+	" AC/ sending pid
+	" MQ/ message
 .rmes:
    jms awake
-   lac o100000
+   lac o100000			" mark this process to "not ready"
    tad u.ulistp i
    dac u.ulistp i
    law 2
    tad u.ulistp
-   dac 9f+t
+   dac 9f+t			" pointer to msg status in proc table
    -1
-   dac 9f+t i
-   jms swap
+   dac 9f+t i			" set to -1 (waiting for message)
+   jms swap			" switch processes
    law 2
    tad u.ulistp
    dac 9f+t
-   lac 9f+t i
-   cma
-   dac u.ac
-   dzm 9f+t i
+   lac 9f+t i			" get msg status word
+   cma				" complement (get sender pid)
+   dac u.ac			" return in user AC
+   dzm 9f+t i			" clear status word
    isz 9f+t
-   lac 9f+t i
-   dac u.mq
-   dzm 9f+t i
+   lac 9f+t i			" get message
+   dac u.mq			" return in user MQ
+   dzm 9f+t i			" clear message
    jmp sysexit
 t = t+1
 
 "** 01-s1.pdf page 16
 	" smes system call
 	" AC/ pid
+	" MQ/ message
 	"   sys smes
+	" returns with message delivered, or error if process does not exit
 .smes:
    lac u.ac			" get pid from user AC
    sna spa			" >0?
@@ -158,10 +166,10 @@ t = t+1
    sad u.ac			" match?
    skp				"  yes
    jmp 1b i			"   no
-   lac lu+2			" get mailbox
+   lac lu+2			" get mailbox status
    sad dm1			" -1?
    jmp 1f			"  yes
-   lac o100000			" no: increment process status
+   lac o100000			" no: bump our process status (to notready?)
    tad u.ulistp i
    dac u.ulistp i
    law 2
@@ -178,35 +186,36 @@ t = t+1
 1:
    -3
    tad 8
-   dac 9f+t
-   lac o700000
+   dac 9f+t			" pointer to dest process ulist entry
+   lac o700000			" complement process status? marks ready??
    tad 9f+t i
    dac 9f+t i
    isz 9f+t
-   isz 9f+t
-   lac u.pid
-   cma
-   dac 9f+t i
-   isz 9f+t
-   lac u.mq
-   dac 9f+t i
+   isz 9f+t			" point to mailbox word?
+   lac u.pid			" get our pid
+   cma				" complement
+   dac 9f+t i			" store in mailbox??
+   isz 9f+t			" advance to next word
+   lac u.mq			" get user MQ
+   dac 9f+t i			" save as message
    jmp okexit
 t = t+1
 
+	" wake up process hanging on rmes for current process??
 awake: 0
    jms searchu; 1f
    jmp awake i
 1: 0				" searchu worker
    lac u.pid			" get caller pid
-   sad lu+2			" match process table entry?
+   sad lu+2			" match mailbox status?
    skp				"  yes
    jmp 1b i			"   no, return
    -3
-   tad 8			" get pointer to pid in process table??
+   tad 8			" get pointer to process table entry
    dac 9f+t			" save in t0
 "** 01-s1.pdf page 17
-   lac o700000			" set high bits
-   tad 9f+t i
+   lac o700000
+   tad 9f+t i			" complement process status (mark ready)??
    dac 9f+t i
    jmp 1b i			" return from worker
 t = t+1
diff --git a/src/sys/s7.s b/src/sys/s7.s
index 27f1139..356e193 100644
--- a/src/sys/s7.s
+++ b/src/sys/s7.s
@@ -330,7 +330,7 @@ putcr: 0
    cla
    jmp putcr i
 
-intrp1:			" here with keyboard interrupt
+intrp1:			" here with TTY interrupt character
    lac d6		" get keyboard special device number
    dac .int1		" save as interrupt source
    lac d1
diff --git a/src/sys/s8.s b/src/sys/s8.s
index afce88c..6b88276 100644
--- a/src/sys/s8.s
+++ b/src/sys/s8.s
@@ -175,8 +175,11 @@ sysdata:			" system data 64 words saved to disk
 	"	4: out/notready??
 	"   bits 3:17 -- disk swap address/8
 	" second word: process pid
-	" third word:  used for smes/rmes
-	" fourth word: ??
+	" third word:  smes/rmes status:
+	"	0: not waiting
+	"	-1: this process waiting (rmes)
+	"	other: complement of sender pid
+	" fourth word: smes message
 ulist:
    0131000;1;0;0
    0031040;0;0;0