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linux-sg2042
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[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>
This commit is contained in:
Stephane Eranian 2006-07-09 21:12:39 -04:00 committed by Linus Torvalds
parent 09075ef0fd
commit b3cf257623
4 changed files with 41 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/i386/kernel/ioport.c
View File

@ -79,6 +79,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
memset(bitmap, 0xff, IO_BITMAP_BYTES);
t->io_bitmap_ptr = bitmap;
set_thread_flag(TIF_IO_BITMAP);
}
/*

50
arch/i386/kernel/process.c
View File

@ -359,16 +359,16 @@ EXPORT_SYMBOL(kernel_thread);
*/
void exit_thread(void)
{
struct task_struct *tsk = current;
struct thread_struct *t = &tsk->thread;
/* The process may have allocated an io port bitmap... nuke it. */
if (unlikely(NULL != t->io_bitmap_ptr)) {
if (unlikely(test_thread_flag(TIF_IO_BITMAP))) {
struct task_struct *tsk = current;
struct thread_struct *t = &tsk->thread;
int cpu = get_cpu();
struct tss_struct *tss = &per_cpu(init_tss, cpu);
kfree(t->io_bitmap_ptr);
t->io_bitmap_ptr = NULL;
clear_thread_flag(TIF_IO_BITMAP);
/*
* Careful, clear this in the TSS too:
*/
@ -387,6 +387,7 @@ void flush_thread(void)
memset(tsk->thread.debugreg, 0, sizeof(unsigned long)*8);
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
clear_tsk_thread_flag(tsk, TIF_DEBUG);
/*
* Forget coprocessor state..
*/
@ -431,7 +432,7 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
savesegment(gs,p->thread.gs);
tsk = current;
if (unlikely(NULL != tsk->thread.io_bitmap_ptr)) {
if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
if (!p->thread.io_bitmap_ptr) {
p->thread.io_bitmap_max = 0;
@ -439,6 +440,7 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
}
memcpy(p->thread.io_bitmap_ptr, tsk->thread.io_bitmap_ptr,
IO_BITMAP_BYTES);
set_tsk_thread_flag(p, TIF_IO_BITMAP);
}
/*
@ -533,10 +535,24 @@ int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
return 1;
}
static inline void
handle_io_bitmap(struct thread_struct *next, struct tss_struct *tss)
static noinline void __switch_to_xtra(struct task_struct *next_p,
struct tss_struct *tss)
{
if (!next->io_bitmap_ptr) {
struct thread_struct *next;
next = &next_p->thread;
if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
set_debugreg(next->debugreg[0], 0);
set_debugreg(next->debugreg[1], 1);
set_debugreg(next->debugreg[2], 2);
set_debugreg(next->debugreg[3], 3);
/* no 4 and 5 */
set_debugreg(next->debugreg[6], 6);
set_debugreg(next->debugreg[7], 7);
}
if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
/*
* Disable the bitmap via an invalid offset. We still cache
* the previous bitmap owner and the IO bitmap contents:
@ -544,6 +560,7 @@ handle_io_bitmap(struct thread_struct *next, struct tss_struct *tss)
tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
return;
}
if (likely(next == tss->io_bitmap_owner)) {
/*
* Previous owner of the bitmap (hence the bitmap content)
@ -671,20 +688,11 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
set_iopl_mask(next->iopl);
/*
* Now maybe reload the debug registers
* Now maybe handle debug registers and/or IO bitmaps
*/
if (unlikely(next->debugreg[7])) {
set_debugreg(next->debugreg[0], 0);
set_debugreg(next->debugreg[1], 1);
set_debugreg(next->debugreg[2], 2);
set_debugreg(next->debugreg[3], 3);
/* no 4 and 5 */
set_debugreg(next->debugreg[6], 6);
set_debugreg(next->debugreg[7], 7);
}
if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr))
handle_io_bitmap(next, tss);
if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW))
|| test_tsk_thread_flag(prev_p, TIF_IO_BITMAP))
__switch_to_xtra(next_p, tss);
disable_tsc(prev_p, next_p);

5
arch/i386/kernel/ptrace.c
View File

@ -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;

7
include/asm-i386/thread_info.h
View File

@ -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.
*