[Bug 1932] New: SMP: SPARC switch_to_first_task_smp creates bad window

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https://www.rtems.org/bugzilla/show_bug.cgi?id=1932

           Summary: SMP: SPARC switch_to_first_task_smp creates bad window
           Product: RTEMS
           Version: HEAD
          Platform: sparc
        OS/Version: RTEMS
            Status: NEW
          Severity: normal
          Priority: P3
         Component: cpukit
        AssignedTo: joel.sherrill at oarcorp.com
        ReportedBy: daniel at gaisler.com


Created attachment 1350
  --> https://www.rtems.org/bugzilla/attachment.cgi?id=1350
_CPU_Context_switch_to_first_task_smp() WIM patch

I have got SMP the smphack01.exe test to successfully complete on a dual core
LEON3 GR712RC ASIC today, the below patch is required.

At some point the interrupt trap handler causes a window-overflow and the
window overflow trap handler crashes when writing to 0. I found that this is
because the WIM was bad, to the window overflow handler uses a uninitialized
stack pointer in a window never used. The below code is rewritten:
 * g3=CWP, not WIM
 * CWP is incremented by done_flushing no need doing that here also
 * I see no reason to create an additional stack frame (save)
 * Must turn off traps when updating WIM (maybe already done by caller?)

Daniel


Index: cpukit/score/cpu/sparc/cpu_asm.S
===================================================================
RCS file:
/home/cvspserver/SMP_Repository/rtems-smp/cpukit/score/cpu/sparc/cpu_asm.S,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 cpu_asm.S
--- cpukit/score/cpu/sparc/cpu_asm.S    31 Mar 2011 18:32:59 -0000    1.1.1.1
+++ cpukit/score/cpu/sparc/cpu_asm.S    7 Oct 2011 11:28:05 -0000
@@ -336,22 +336,22 @@
  *
  *  This routine is only used to switch to the first task on a
  *  secondary core in an SMP configuration.  We do not need to
- *  flush all the windows and, in fact, this can be dangerous
+ *  flush any windows and, in fact, this can be dangerous
  *  as they may or may not be initialized properly.  So we just
  *  reinitialize the PSR and WIM.
  */
         PUBLIC(_CPU_Context_switch_to_first_task_smp)
 SYM(_CPU_Context_switch_to_first_task_smp):
-        save    %sp, -CPU_MINIMUM_STACK_FRAME_SIZE, %sp
-
-        mov    %psr, %g1             ! Initialize WIM
-    add    %g1, 1, %g2
-    and    %g2, 0x7, %g2
-    set    1, %g3
-    sll    %g3, %g2, %g3
-        mov     %g3, %wim
-        ba      done_flushing
-        mov     %i0, %o1                      ! in the delay slot
+    mov    %psr, %g1        ! Turn of traps when modifying WIM
+    andn    %g1, SPARC_PSR_ET_MASK, %g1
+    mov    %g1, %psr
+    /* WIM and PSR will be set in done_flushing, it need args:
+     * g1=PSR, g3=CWP, o1=Context
+     */
+    and    %g1, SPARC_NUMBER_OF_REGISTER_WINDOWS - 1, %g3
+    nop
+    mov    %o0, %o1        ! in the delay slot
+    ba,a    done_flushing
 #endif

 /* end of file */

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