Changeset 245e8399 in mainline

Timestamp:

2009-12-25T19:17:27Z (15 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

eacb957

Parents:

3766467

Message:

Flush windows in context_save_arch() instead of context_restore_arch().

Files:

• kernel/arch/sparc64/src/context.S (modified) (3 diffs)
• kernel/arch/sparc64/src/trap/trap_table.S (modified) (1 diff)
• uspace/lib/libc/arch/sparc64/src/fibril.S (modified) (2 diffs)

kernel/arch/sparc64/src/context.S

@@ -28 +28 @@
 
 #include <arch/context_offset.h>
-
-/**
- * Both context_save_arch() and context_restore_arch() are
- * leaf-optimized procedures. This kind of optimization
- * is very important and prevents any implicit window
- * spill/fill/clean traps in these very core kernel
- * functions.
- */
-        
-#include <arch/context_offset.h>
+#include <arch/arch.h>
+#include <arch/regdef.h>
 
 .text   
@@ -44 +36 @@
 .global context_restore_arch
 
+/*
+ * context_save_arch() is required not to create its own stack frame. See the
+ * generic context.h for explanation.
+ */
 context_save_arch:
+        #
+        # Force all our active register windows to memory so that we can find
+        # them there even if e.g. the thread is migrated to another processor.
+        #
+        flushw
+
         CONTEXT_SAVE_ARCH_CORE %o0
         retl
@@ -51 +53 @@
 context_restore_arch:
         #
-        # Flush all active windows.
-        # This is essential, because CONTEXT_LOAD overwrites
-        # %sp of CWP - 1 with the value written to %fp of CWP.
-        # Flushing all active windows mitigates this problem
-        # as CWP - 1 becomes the overlap window.
+        # Forget all previous windows, they are not going to be needed again.
+        # Enforce a window fill on the next RESTORE instruction by setting
+        # CANRESTORE to zero and other window configuration registers
+        # accordingly. Note that the same can be achieved by executing the
+        # FLUSHW instruction, but since we don't need to remember the previous
+        # windows, we do the former and save thus some unnecessary window
+        # spills.
         #
-        flushw
-        
+        rdpr %pstate, %l0
+        andn %l0, PSTATE_IE_BIT, %l1
+        wrpr %l1, %pstate
+        wrpr %g0, 0, %canrestore
+        wrpr %g0, 0, %otherwin
+        wrpr %g0, NWINDOWS - 2, %cansave
+        wrpr %l0, %pstate
+
         CONTEXT_RESTORE_ARCH_CORE %o0
         retl

kernel/arch/sparc64/src/trap/trap_table.S

@@ -652 +652 @@
          * spilled to kernel memory (i.e. register window buffer). Moreover,
          * if the scheduler was called in the meantime, all valid windows
-         * belonging to other threads were spilled by context_restore().
+         * belonging to other threads were spilled by context_save().
          * If OTHERWIN is non-zero, then some userspace windows are still
          * valid. Others might have been spilled. However, the CWP pointer

uspace/lib/libc/arch/sparc64/src/fibril.S

@@ -35 +35 @@
 
 context_save:
+        #
+        # We rely on the kernel to flush our active register windows to memory
+        # should a thread switch occur.
+        #
         CONTEXT_SAVE_ARCH_CORE %o0
         retl
@@ -42 +46 @@
         #
         # Flush all active windows.
-        # This is essential, because CONTEXT_LOAD overwrites
-        # %sp of CWP - 1 with the value written to %fp of CWP.
-        # Flushing all active windows mitigates this problem
-        # as CWP - 1 becomes the overlap window.
-        #               
+        # This is essential, because CONTEXT_RESTORE_ARCH_CORE overwrites %sp of
+        # CWP - 1 with the value written to %fp of CWP.  Flushing all active
+        # windows mitigates this problem as CWP - 1 becomes the overlap window.
+        #
         flushw