[Openmcl-cvs-notifications] r10623 - in /trunk/source/lisp-kernel: ppc-exceptions.c ppc-spentry.s

[gb at clozure.com]

Author: gb
Date: Mon Sep  8 00:06:21 2008
New Revision: 10623

Log:
Use a different set of conventions (the label
egc_store_node_conditional_test and the state of cr0[eq]) to determine
whether or not a store_node_conditional has completed.

If pc_luser_xp interrupts/completes set_hash_key, ensure that it
stores arg_z.  (Was storing 0, which, if it ever happened, was
obviously the wrong thing to do.)

Modified:
    trunk/source/lisp-kernel/ppc-exceptions.c
    trunk/source/lisp-kernel/ppc-spentry.s

Modified: trunk/source/lisp-kernel/ppc-exceptions.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
--- trunk/source/lisp-kernel/ppc-exceptions.c (original)
+++ trunk/source/lisp-kernel/ppc-exceptions.c Mon Sep  8 00:06:21 2008
@@ -1831,6 +1831,7 @@
   egc_write_barrier_start,
   egc_write_barrier_end, =

   egc_store_node_conditional, =

+  egc_store_node_conditional_test,
   egc_set_hash_key,
   egc_gvset,
   egc_rplaca,
@@ -1857,17 +1858,19 @@
     Boolean need_store =3D true, need_check_memo =3D true, need_memoize_ro=
ot =3D false;
 =

     if (program_counter >=3D &egc_store_node_conditional) {
-      if ((program_counter =3D=3D &egc_store_node_conditional) || ! (xpCCR=
(xp) & 0x20000000)) {
-        /* The conditional store either hasn't been attempted yet, or
-           has failed.  No need to adjust the PC, or do memoization. */
-        return;
+      if ((program_counter < &egc_store_node_conditional_test) ||
+	  ((program_counter =3D=3D &egc_store_node_conditional_test) &&
+	   (! (xpCCR(xp) & 0x20000000)))) {
+	/* The conditional store either hasn't been attempted yet, or
+	   has failed.  No need to adjust the PC, or do memoization. */
+	return;
       }
-      val =3D xpGPR(xp,arg_z);
       ea =3D (LispObj*)(xpGPR(xp,arg_x) + xpGPR(xp,imm4));
       xpGPR(xp,arg_z) =3D t_value;
       need_store =3D false;
     } else if (program_counter >=3D &egc_set_hash_key) {
       root =3D xpGPR(xp,arg_x);
+      val =3D xpGPR(xp,arg_z);
       ea =3D (LispObj *) (root+xpGPR(xp,arg_y)+misc_data_offset);
       need_memoize_root =3D true;
     } else if (program_counter >=3D &egc_gvset) {

Modified: trunk/source/lisp-kernel/ppc-spentry.s
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
--- trunk/source/lisp-kernel/ppc-spentry.s (original)
+++ trunk/source/lisp-kernel/ppc-spentry.s Mon Sep  8 00:06:21 2008
@@ -605,17 +605,23 @@
         __(isync)
         __(blr)
         =

-/* This is a little trickier: the first instruction clears the EQ bit in C=
R0; */
-/* the only way that it can get set is if the conditional store succeeds. =
  */
-/* So: */
-/*   a) if we're interrupted on the first instruction, or if we're  */
-/*      interrupted on a subsequent instruction but CR0[EQ] is clear, the =
 */
-/*      condtional store hasn't succeeded yet.  We don't have to adjust th=
e  */
-/*      PC in this case; when the thread's resumed, the conditional store =
*/
-/*      will be (re-)attempted and will eventually either succeed or fail.=
 */
-/*   b) if the CR0[EQ] bit is set (on some instruction other than the firs=
t), */
-/*      the handler can decide if/how to handle memoization.  The handler =
*/
-/*      should set the PC to the LR, and set arg_z to T. */
+/*
+   Interrupt handling (in pc_luser_xp()) notes:	=

+   If we are in this function and before the test which follows the
+   conditional (at egc_store_node_conditional), or at that test
+   and cr0[eq] is clear, pc_luser_xp() should just let this continue
+   (we either haven't done the store conditional yet, or got a
+   possibly transient failure.)  If we're at that test and the
+   cr0[EQ] bit is set, then the conditional store succeeded and
+   we have to atomically memoize the possible intergenerational
+   reference.  Note that the local labels 4 and 5 are at or beyond
+  'egc_write_barrier_end'
+
+   N.B:	it's not possible to really understand what's going on just
+   by the state of the cr0[eq] bit.  A transient failure in the
+   conditional stores that handle memoization might clear cr0[eq]
+   without having completed the memoization.
+*/
 =

         .globl C(egc_store_node_conditional)
         .globl C(egc_write_barrier_end)
@@ -629,6 +635,8 @@
         __(cmpr(cr1,temp1,arg_y))
         __(bne cr1,3f)
         __(strcx(arg_z,arg_x,imm4))
+	.globl C(egc_store_node_conditional_test)
+C(egc_store_node_conditional_test):	=

         __(bne 1b)
         __(isync)
         __(add imm0,imm4,arg_x)
@@ -650,9 +658,9 @@
         __(bne- 2b)
         __(isync)
         __(b 5f)
+C(egc_write_barrier_end):
 3:      __(li imm0,RESERVATION_DISCHARGE)
         __(strcx(rzero,0,imm0))
-C(egc_write_barrier_end):
 4:      __(li arg_z,nil_value)
         __(blr)
 5:      __(li arg_z,t_value)