[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, 4 insertions, 1 deletions

diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c
index fd7eaf7866e0..d3db03f4085d 100644
--- a/arch/i386/kernel/ptrace.c
+++ b/arch/i386/kernel/ptrace.c
@@ -468,8 +468,11 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                                   for(i=0; i<4; i++)
                                           if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
                                                   goto out_tsk;
+                                  if (data)
+                                          set_tsk_thread_flag(child, TIF_DEBUG);
+                                  else
+                                          clear_tsk_thread_flag(child, TIF_DEBUG);
                           }
-
                           addr -= (long) &dummy->u_debugreg;
                           addr = addr >> 2;
                           child->thread.debugreg[addr] = data;