Changes in / [eacb957:c26eb39] in mainline

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>
-#include <arch/arch.h>
-#include <arch/regdef.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>
 
 .text   
@@ -36 +44 @@
 .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
@@ -53 +51 @@
 context_restore_arch:
         #
-        # 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.
+        # 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.
         #
-        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
-
+        flushw
+        
         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_save().
+         * belonging to other threads were spilled by context_restore().
          * 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
@@ -46 +42 @@
         #
         # Flush all active windows.
-        # 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.
-        #
+        # 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.
+        #               
         flushw