a0458b07c1
sh port of the sLeAZY-fpu feature currently implemented for some architectures such us i386. Right now the SH kernel has a 100% lazy fpu behaviour. This is of course great for applications that have very sporadic or no FPU use. However for very frequent FPU users... you take an extra trap every context switch. The patch below adds a simple heuristic to this code: after 5 consecutive context switches of FPU use, the lazy behavior is disabled and the context gets restored every context switch. After 256 switches, this is reset and the 100% lazy behavior is returned. Tests with LMbench showed no regression. I saw a little improvement due to the prefetching (~2%). The tests below also show that, with this sLeazy patch, indeed, the number of FPU exceptions is reduced. To test this. I hacked the lat_ctx LMBench to use the FPU a little more. sLeasy implementation =========================================== switch_to calls | 79326 sleasy calls | 42577 do_fpu_state_restore calls| 59232 restore_fpu calls | 59032 Exceptions: 0x800 (FPU disabled ): 16604 100% Leazy (default implementation) =========================================== switch_to calls | 79690 do_fpu_state_restore calls | 53299 restore_fpu calls | 53101 Exceptions: 0x800 (FPU disabled ): 53273 Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com> Signed-off-by: Stuart Menefy <stuart.menefy@st.com> Signed-off-by: Paul Mundt <lethal@linux-sh.org>
448 lines
10 KiB
C
448 lines
10 KiB
C
/*
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* arch/sh/kernel/process.c
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*
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* This file handles the architecture-dependent parts of process handling..
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*
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* Copyright (C) 1995 Linus Torvalds
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*
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* SuperH version: Copyright (C) 1999, 2000 Niibe Yutaka & Kaz Kojima
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* Copyright (C) 2006 Lineo Solutions Inc. support SH4A UBC
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* Copyright (C) 2002 - 2008 Paul Mundt
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*/
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <linux/elfcore.h>
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#include <linux/pm.h>
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#include <linux/kallsyms.h>
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#include <linux/kexec.h>
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#include <linux/kdebug.h>
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#include <linux/tick.h>
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#include <linux/reboot.h>
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#include <linux/fs.h>
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#include <linux/ftrace.h>
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#include <linux/preempt.h>
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#include <asm/uaccess.h>
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#include <asm/mmu_context.h>
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#include <asm/pgalloc.h>
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#include <asm/system.h>
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#include <asm/ubc.h>
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#include <asm/fpu.h>
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#include <asm/syscalls.h>
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#include <asm/watchdog.h>
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int ubc_usercnt = 0;
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#ifdef CONFIG_32BIT
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static void watchdog_trigger_immediate(void)
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{
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sh_wdt_write_cnt(0xFF);
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sh_wdt_write_csr(0xC2);
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}
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void machine_restart(char * __unused)
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{
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local_irq_disable();
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/* Use watchdog timer to trigger reset */
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watchdog_trigger_immediate();
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while (1)
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cpu_sleep();
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}
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#else
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void machine_restart(char * __unused)
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{
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/* SR.BL=1 and invoke address error to let CPU reset (manual reset) */
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asm volatile("ldc %0, sr\n\t"
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"mov.l @%1, %0" : : "r" (0x10000000), "r" (0x80000001));
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}
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#endif
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void machine_halt(void)
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{
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local_irq_disable();
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while (1)
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cpu_sleep();
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}
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void machine_power_off(void)
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{
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if (pm_power_off)
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pm_power_off();
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}
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void show_regs(struct pt_regs * regs)
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{
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printk("\n");
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printk("Pid : %d, Comm: \t\t%s\n", task_pid_nr(current), current->comm);
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printk("CPU : %d \t\t%s (%s %.*s)\n\n",
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smp_processor_id(), print_tainted(), init_utsname()->release,
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(int)strcspn(init_utsname()->version, " "),
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init_utsname()->version);
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print_symbol("PC is at %s\n", instruction_pointer(regs));
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print_symbol("PR is at %s\n", regs->pr);
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printk("PC : %08lx SP : %08lx SR : %08lx ",
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regs->pc, regs->regs[15], regs->sr);
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#ifdef CONFIG_MMU
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printk("TEA : %08x\n", ctrl_inl(MMU_TEA));
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#else
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printk("\n");
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#endif
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printk("R0 : %08lx R1 : %08lx R2 : %08lx R3 : %08lx\n",
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regs->regs[0],regs->regs[1],
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regs->regs[2],regs->regs[3]);
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printk("R4 : %08lx R5 : %08lx R6 : %08lx R7 : %08lx\n",
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regs->regs[4],regs->regs[5],
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regs->regs[6],regs->regs[7]);
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printk("R8 : %08lx R9 : %08lx R10 : %08lx R11 : %08lx\n",
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regs->regs[8],regs->regs[9],
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regs->regs[10],regs->regs[11]);
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printk("R12 : %08lx R13 : %08lx R14 : %08lx\n",
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regs->regs[12],regs->regs[13],
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regs->regs[14]);
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printk("MACH: %08lx MACL: %08lx GBR : %08lx PR : %08lx\n",
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regs->mach, regs->macl, regs->gbr, regs->pr);
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show_trace(NULL, (unsigned long *)regs->regs[15], regs);
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show_code(regs);
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}
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/*
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* Create a kernel thread
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*/
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ATTRIB_NORET void kernel_thread_helper(void *arg, int (*fn)(void *))
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{
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do_exit(fn(arg));
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}
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/* Don't use this in BL=1(cli). Or else, CPU resets! */
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int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
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{
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struct pt_regs regs;
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int pid;
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memset(®s, 0, sizeof(regs));
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regs.regs[4] = (unsigned long)arg;
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regs.regs[5] = (unsigned long)fn;
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regs.pc = (unsigned long)kernel_thread_helper;
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regs.sr = (1 << 30);
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/* Ok, create the new process.. */
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pid = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0,
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®s, 0, NULL, NULL);
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return pid;
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}
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/*
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* Free current thread data structures etc..
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*/
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void exit_thread(void)
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{
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if (current->thread.ubc_pc) {
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current->thread.ubc_pc = 0;
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ubc_usercnt -= 1;
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}
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}
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void flush_thread(void)
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{
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#if defined(CONFIG_SH_FPU)
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struct task_struct *tsk = current;
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/* Forget lazy FPU state */
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clear_fpu(tsk, task_pt_regs(tsk));
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clear_used_math();
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#endif
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}
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void release_thread(struct task_struct *dead_task)
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{
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/* do nothing */
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}
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/* Fill in the fpu structure for a core dump.. */
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int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
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{
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int fpvalid = 0;
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#if defined(CONFIG_SH_FPU)
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struct task_struct *tsk = current;
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fpvalid = !!tsk_used_math(tsk);
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if (fpvalid)
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fpvalid = !fpregs_get(tsk, NULL, 0,
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sizeof(struct user_fpu_struct),
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fpu, NULL);
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#endif
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return fpvalid;
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}
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asmlinkage void ret_from_fork(void);
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int copy_thread(unsigned long clone_flags, unsigned long usp,
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unsigned long unused,
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struct task_struct *p, struct pt_regs *regs)
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{
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struct thread_info *ti = task_thread_info(p);
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struct pt_regs *childregs;
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#if defined(CONFIG_SH_FPU) || defined(CONFIG_SH_DSP)
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struct task_struct *tsk = current;
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#endif
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#if defined(CONFIG_SH_FPU)
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unlazy_fpu(tsk, regs);
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p->thread.fpu = tsk->thread.fpu;
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copy_to_stopped_child_used_math(p);
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#endif
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#if defined(CONFIG_SH_DSP)
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if (is_dsp_enabled(tsk)) {
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/* We can use the __save_dsp or just copy the struct:
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* __save_dsp(p);
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* p->thread.dsp_status.status |= SR_DSP
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*/
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p->thread.dsp_status = tsk->thread.dsp_status;
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}
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#endif
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childregs = task_pt_regs(p);
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*childregs = *regs;
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if (user_mode(regs)) {
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childregs->regs[15] = usp;
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ti->addr_limit = USER_DS;
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} else {
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childregs->regs[15] = (unsigned long)childregs;
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ti->addr_limit = KERNEL_DS;
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}
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if (clone_flags & CLONE_SETTLS)
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childregs->gbr = childregs->regs[0];
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childregs->regs[0] = 0; /* Set return value for child */
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p->thread.sp = (unsigned long) childregs;
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p->thread.pc = (unsigned long) ret_from_fork;
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p->thread.ubc_pc = 0;
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return 0;
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}
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/* Tracing by user break controller. */
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static void ubc_set_tracing(int asid, unsigned long pc)
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{
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#if defined(CONFIG_CPU_SH4A)
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unsigned long val;
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val = (UBC_CBR_ID_INST | UBC_CBR_RW_READ | UBC_CBR_CE);
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val |= (UBC_CBR_AIE | UBC_CBR_AIV_SET(asid));
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ctrl_outl(val, UBC_CBR0);
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ctrl_outl(pc, UBC_CAR0);
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ctrl_outl(0x0, UBC_CAMR0);
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ctrl_outl(0x0, UBC_CBCR);
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val = (UBC_CRR_RES | UBC_CRR_PCB | UBC_CRR_BIE);
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ctrl_outl(val, UBC_CRR0);
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/* Read UBC register that we wrote last, for checking update */
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val = ctrl_inl(UBC_CRR0);
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#else /* CONFIG_CPU_SH4A */
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ctrl_outl(pc, UBC_BARA);
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#ifdef CONFIG_MMU
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ctrl_outb(asid, UBC_BASRA);
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#endif
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ctrl_outl(0, UBC_BAMRA);
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if (current_cpu_data.type == CPU_SH7729 ||
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current_cpu_data.type == CPU_SH7710 ||
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current_cpu_data.type == CPU_SH7712 ||
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current_cpu_data.type == CPU_SH7203){
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ctrl_outw(BBR_INST | BBR_READ | BBR_CPU, UBC_BBRA);
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ctrl_outl(BRCR_PCBA | BRCR_PCTE, UBC_BRCR);
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} else {
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ctrl_outw(BBR_INST | BBR_READ, UBC_BBRA);
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ctrl_outw(BRCR_PCBA, UBC_BRCR);
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}
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#endif /* CONFIG_CPU_SH4A */
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}
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/*
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* switch_to(x,y) should switch tasks from x to y.
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*
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*/
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__notrace_funcgraph struct task_struct *
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__switch_to(struct task_struct *prev, struct task_struct *next)
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{
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struct thread_struct *next_t = &next->thread;
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#if defined(CONFIG_SH_FPU)
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unlazy_fpu(prev, task_pt_regs(prev));
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/* we're going to use this soon, after a few expensive things */
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if (next->fpu_counter > 5)
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prefetch(&next_t->fpu.hard);
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#endif
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#ifdef CONFIG_MMU
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/*
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* Restore the kernel mode register
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* k7 (r7_bank1)
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*/
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asm volatile("ldc %0, r7_bank"
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: /* no output */
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: "r" (task_thread_info(next)));
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#endif
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/* If no tasks are using the UBC, we're done */
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if (ubc_usercnt == 0)
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/* If no tasks are using the UBC, we're done */;
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else if (next->thread.ubc_pc && next->mm) {
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int asid = 0;
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#ifdef CONFIG_MMU
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asid |= cpu_asid(smp_processor_id(), next->mm);
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#endif
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ubc_set_tracing(asid, next->thread.ubc_pc);
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} else {
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#if defined(CONFIG_CPU_SH4A)
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ctrl_outl(UBC_CBR_INIT, UBC_CBR0);
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ctrl_outl(UBC_CRR_INIT, UBC_CRR0);
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#else
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ctrl_outw(0, UBC_BBRA);
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ctrl_outw(0, UBC_BBRB);
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#endif
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}
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#if defined(CONFIG_SH_FPU)
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/* If the task has used fpu the last 5 timeslices, just do a full
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* restore of the math state immediately to avoid the trap; the
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* chances of needing FPU soon are obviously high now
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*/
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if (next->fpu_counter > 5) {
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fpu_state_restore(task_pt_regs(next));
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}
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#endif
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return prev;
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}
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asmlinkage int sys_fork(unsigned long r4, unsigned long r5,
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unsigned long r6, unsigned long r7,
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struct pt_regs __regs)
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{
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#ifdef CONFIG_MMU
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struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
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return do_fork(SIGCHLD, regs->regs[15], regs, 0, NULL, NULL);
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#else
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/* fork almost works, enough to trick you into looking elsewhere :-( */
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return -EINVAL;
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#endif
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}
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asmlinkage int sys_clone(unsigned long clone_flags, unsigned long newsp,
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unsigned long parent_tidptr,
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unsigned long child_tidptr,
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struct pt_regs __regs)
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{
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struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
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if (!newsp)
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newsp = regs->regs[15];
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return do_fork(clone_flags, newsp, regs, 0,
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(int __user *)parent_tidptr,
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(int __user *)child_tidptr);
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}
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/*
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* This is trivial, and on the face of it looks like it
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* could equally well be done in user mode.
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*
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* Not so, for quite unobvious reasons - register pressure.
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* In user mode vfork() cannot have a stack frame, and if
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* done by calling the "clone()" system call directly, you
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* do not have enough call-clobbered registers to hold all
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* the information you need.
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*/
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asmlinkage int sys_vfork(unsigned long r4, unsigned long r5,
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unsigned long r6, unsigned long r7,
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struct pt_regs __regs)
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{
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struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
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return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->regs[15], regs,
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0, NULL, NULL);
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}
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/*
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* sys_execve() executes a new program.
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*/
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asmlinkage int sys_execve(char __user *ufilename, char __user * __user *uargv,
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char __user * __user *uenvp, unsigned long r7,
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struct pt_regs __regs)
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{
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struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
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int error;
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char *filename;
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filename = getname(ufilename);
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error = PTR_ERR(filename);
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if (IS_ERR(filename))
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goto out;
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error = do_execve(filename, uargv, uenvp, regs);
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putname(filename);
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out:
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return error;
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}
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unsigned long get_wchan(struct task_struct *p)
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{
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unsigned long pc;
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if (!p || p == current || p->state == TASK_RUNNING)
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return 0;
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/*
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* The same comment as on the Alpha applies here, too ...
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*/
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pc = thread_saved_pc(p);
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#ifdef CONFIG_FRAME_POINTER
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if (in_sched_functions(pc)) {
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unsigned long schedule_frame = (unsigned long)p->thread.sp;
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return ((unsigned long *)schedule_frame)[21];
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}
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#endif
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return pc;
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}
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asmlinkage void break_point_trap(void)
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{
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/* Clear tracing. */
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#if defined(CONFIG_CPU_SH4A)
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ctrl_outl(UBC_CBR_INIT, UBC_CBR0);
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ctrl_outl(UBC_CRR_INIT, UBC_CRR0);
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#else
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ctrl_outw(0, UBC_BBRA);
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ctrl_outw(0, UBC_BBRB);
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ctrl_outl(0, UBC_BRCR);
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#endif
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current->thread.ubc_pc = 0;
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ubc_usercnt -= 1;
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force_sig(SIGTRAP, current);
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}
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