From b3cf257623fabd8f1ee6700a6d328cc1c5da5a1d Mon Sep 17 00:00:00 2001 From: Stephane Eranian Date: Sun, 9 Jul 2006 21:12:39 -0400 Subject: [PATCH] [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 Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Acked-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/i386/kernel/ioport.c | 1 + arch/i386/kernel/process.c | 50 ++++++++++++++++++++-------------- arch/i386/kernel/ptrace.c | 5 +++- include/asm-i386/thread_info.h | 7 +++++ 4 files changed, 41 insertions(+), 22 deletions(-) diff --git a/arch/i386/kernel/ioport.c b/arch/i386/kernel/ioport.c index 79026f026b85..498e8bc197d5 100644 --- a/arch/i386/kernel/ioport.c +++ b/arch/i386/kernel/ioport.c @@ -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); } /* diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index 94e2c87edeaa..923bb292f47f 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -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); 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; 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<