[sginsberg] 56333: - Even while I love having the trap/fpu/context code in C, the bugs this switch introduced continue to amaze me. This time, fix a bug from 45156 when KiFlushNPXState was rewritte...

Author: sginsberg
Date: Fri Apr  6 20:13:33 2012
New Revision: 56333

URL: http://svn.reactos.org/svn/reactos?rev=56333&view=rev
Log:
- Even while I love having the trap/fpu/context code in C, the bugs this switch introduced
continue to amaze me. This time, fix a bug from 45156 when KiFlushNPXState was rewritten
in C. The C version could miss to restore the interrupt state, which would lead to
interrupts being disabled when it was not expected. This "interrupt leak" was
seen in the page fault handler if a page fault occurred after interrupts had been disabled
(which had sometimes been observed to occur on the test server during exception handling
and thread creation when KiFlushNPXState had been called). This didn't completely hang
the system because during thread creation (and other system calls where this may have
happened) interrupts would be re-enabled when returning to user mode when restoring
eflags, and the exception handling would result in a system call which would enable
interrupts again (it appears exception handler would have run with interrupts disabled,
though!). This is now fixed, as well as any other issues this might have caused. The hack
in the page fault handler remains until another issue has been fixed.

Modified:
    trunk/reactos/ntoskrnl/ke/i386/cpu.c

Modified: trunk/reactos/ntoskrnl/ke/i386/cpu.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/ke/i386/cpu.c?rev…
==============================================================================
--- trunk/reactos/ntoskrnl/ke/i386/cpu.c [iso-8859-1] (original)
+++ trunk/reactos/ntoskrnl/ke/i386/cpu.c [iso-8859-1] Fri Apr  6 20:13:33 2012
@@ -1323,7 +1323,12 @@
     if (Thread->NpxState != NPX_STATE_LOADED)
     {
         /* If there's nothing to load, quit */
-        if (!SaveArea) return;
+        if (!SaveArea)
+        {
+            /* Restore interrupt state and return */
+            __writeeflags(EFlags);
+            return;
+        }
 
         /* Need FXSR support for this */
         ASSERT(KeI386FxsrPresent == TRUE);