[PATCH] i386: use thread_info flags for debug regs and IO bitmaps

Use thread info flags to track use of debug registers and IO bitmaps.

 - add TIF_DEBUG to track when debug registers are active
 - add TIF_IO_BITMAP to track when I/O bitmap is used
 - modify __switch_to() to use the new TIF flags

Performance tested on Pentium II, ten runs of LMbench context switch
benchmark (smaller is better:)

	before	after
avg	3.65	3.39
min	3.55	3.33

Signed-off-by: Stephane Eranian <eranian@hpl.hp.com>
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Acked-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/asm-i386/thread_info.h b/include/asm-i386/thread_info.h
index 2833fa2c0dd0..54d6d7aea938 100644
--- a/include/asm-i386/thread_info.h
+++ b/include/asm-i386/thread_info.h
@@ -140,6 +140,8 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_SECCOMP             8       /* secure computing */
 #define TIF_RESTORE_SIGMASK     9       /* restore signal mask in do_signal() */
 #define TIF_MEMDIE              16
+#define TIF_DEBUG               17      /* uses debug registers */
+#define TIF_IO_BITMAP           18      /* uses I/O bitmap */
 
 #define _TIF_SYSCALL_TRACE      (1<<TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME      (1<<TIF_NOTIFY_RESUME)
@@ -151,6 +153,8 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_SYSCALL_AUDIT      (1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP            (1<<TIF_SECCOMP)
 #define _TIF_RESTORE_SIGMASK    (1<<TIF_RESTORE_SIGMASK)
+#define _TIF_DEBUG              (1<<TIF_DEBUG)
+#define _TIF_IO_BITMAP          (1<<TIF_IO_BITMAP)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK \
@@ -159,6 +163,9 @@ static inline struct thread_info *current_thread_info(void)
 /* work to do on any return to u-space */
 #define _TIF_ALLWORK_MASK       (0x0000FFFF & ~_TIF_SECCOMP)
 
+/* flags to check in __switch_to() */
+#define _TIF_WORK_CTXSW (_TIF_DEBUG|_TIF_IO_BITMAP)
+
 /*
  * Thread-synchronous status.
  *