1
0
Fork 0

[ARM] Add thread_notify infrastructure

Some machine classes need to allow VFP support to be built into the
kernel, but still allow the kernel to run even though VFP isn't
present.  Unfortunately, the kernel hard-codes VFP instructions
into the thread switch, which prevents this being run-time selectable.

Solve this by introducing a notifier which things such as VFP can
hook into to be informed of events which affect the VFP subsystem
(eg, creation and destruction of threads, switches between threads.)

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
hifive-unleashed-5.1
Russell King 2006-06-21 13:31:52 +01:00 committed by Russell King
parent 52ab3f3dc7
commit d6551e884c
6 changed files with 135 additions and 59 deletions

View File

@ -20,6 +20,7 @@
#include <asm/glue.h>
#include <asm/vfpmacros.h>
#include <asm/arch/entry-macro.S>
#include <asm/thread_notify.h>
#include "entry-header.S"
@ -560,10 +561,8 @@ ENTRY(__switch_to)
add ip, r1, #TI_CPU_SAVE
ldr r3, [r2, #TI_TP_VALUE]
stmia ip!, {r4 - sl, fp, sp, lr} @ Store most regs on stack
#ifndef CONFIG_MMU
add r2, r2, #TI_CPU_DOMAIN
#else
ldr r6, [r2, #TI_CPU_DOMAIN]!
#ifdef CONFIG_MMU
ldr r6, [r2, #TI_CPU_DOMAIN]
#endif
#if __LINUX_ARM_ARCH__ >= 6
#ifdef CONFIG_CPU_32v6K
@ -585,21 +584,20 @@ ENTRY(__switch_to)
#ifdef CONFIG_MMU
mcr p15, 0, r6, c3, c0, 0 @ Set domain register
#endif
#ifdef CONFIG_VFP
@ Always disable VFP so we can lazily save/restore the old
@ state. This occurs in the context of the previous thread.
VFPFMRX r4, FPEXC
bic r4, r4, #FPEXC_ENABLE
VFPFMXR FPEXC, r4
#endif
#if defined(CONFIG_IWMMXT)
bl iwmmxt_task_switch
#elif defined(CONFIG_CPU_XSCALE)
add r4, r2, #40 @ cpu_context_save->extra
add r4, r2, #TI_CPU_DOMAIN + 40 @ cpu_context_save->extra
ldmib r4, {r4, r5}
mar acc0, r4, r5
#endif
ldmib r2, {r4 - sl, fp, sp, pc} @ Load all regs saved previously
mov r5, r0
add r4, r2, #TI_CPU_SAVE
ldr r0, =thread_notify_head
mov r1, #THREAD_NOTIFY_SWITCH
bl atomic_notifier_call_chain
mov r0, r5
ldmia r4, {r4 - sl, fp, sp, pc} @ Load all regs saved previously
__INIT

View File

@ -285,7 +285,7 @@ ENTRY(iwmmxt_task_switch)
bne 1f @ yes: block them for next task
ldr r5, =concan_owner
add r6, r2, #(TI_IWMMXT_STATE - TI_CPU_DOMAIN) @ get next task Concan save area
add r6, r2, #TI_IWMMXT_STATE @ get next task Concan save area
ldr r5, [r5] @ get current Concan owner
teq r5, r6 @ next task owns it?
movne pc, lr @ no: leave Concan disabled

View File

@ -33,6 +33,7 @@
#include <asm/leds.h>
#include <asm/processor.h>
#include <asm/system.h>
#include <asm/thread_notify.h>
#include <asm/uaccess.h>
#include <asm/mach/time.h>
@ -338,13 +339,9 @@ void exit_thread(void)
{
}
static void default_fp_init(union fp_state *fp)
{
memset(fp, 0, sizeof(union fp_state));
}
ATOMIC_NOTIFIER_HEAD(thread_notify_head);
void (*fp_init)(union fp_state *) = default_fp_init;
EXPORT_SYMBOL(fp_init);
EXPORT_SYMBOL_GPL(thread_notify_head);
void flush_thread(void)
{
@ -353,22 +350,21 @@ void flush_thread(void)
memset(thread->used_cp, 0, sizeof(thread->used_cp));
memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
memset(&thread->fpstate, 0, sizeof(union fp_state));
thread_notify(THREAD_NOTIFY_FLUSH, thread);
#if defined(CONFIG_IWMMXT)
iwmmxt_task_release(thread);
#endif
fp_init(&thread->fpstate);
#if defined(CONFIG_VFP)
vfp_flush_thread(&thread->vfpstate);
#endif
}
void release_thread(struct task_struct *dead_task)
{
#if defined(CONFIG_VFP)
vfp_release_thread(&task_thread_info(dead_task)->vfpstate);
#endif
struct thread_info *thread = task_thread_info(dead_task);
thread_notify(THREAD_NOTIFY_RELEASE, thread);
#if defined(CONFIG_IWMMXT)
iwmmxt_task_release(task_thread_info(dead_task));
iwmmxt_task_release(thread);
#endif
}

View File

@ -33,7 +33,8 @@
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/init.h>
/* XXX */
#include <asm/thread_notify.h>
#include "softfloat.h"
#include "fpopcode.h"
@ -56,16 +57,28 @@ void fp_send_sig(unsigned long sig, struct task_struct *p, int priv);
extern char fpe_type[];
#endif
static int nwfpe_notify(struct notifier_block *self, unsigned long cmd, void *v)
{
struct thread_info *thread = v;
if (cmd == THREAD_NOTIFY_FLUSH)
nwfpe_init_fpa(&thread->fpstate);
return NOTIFY_DONE;
}
static struct notifier_block nwfpe_notifier_block = {
.notifier_call = nwfpe_notify,
};
/* kernel function prototypes required */
void fp_setup(void);
/* external declarations for saved kernel symbols */
extern void (*kern_fp_enter)(void);
extern void (*fp_init)(union fp_state *);
/* Original value of fp_enter from kernel before patched by fpe_init. */
static void (*orig_fp_enter)(void);
static void (*orig_fp_init)(union fp_state *);
/* forward declarations */
extern void nwfpe_enter(void);
@ -88,20 +101,20 @@ static int __init fpe_init(void)
printk(KERN_WARNING "NetWinder Floating Point Emulator V0.97 ("
NWFPE_BITS " precision)\n");
thread_register_notifier(&nwfpe_notifier_block);
/* Save pointer to the old FP handler and then patch ourselves in */
orig_fp_enter = kern_fp_enter;
orig_fp_init = fp_init;
kern_fp_enter = nwfpe_enter;
fp_init = nwfpe_init_fpa;
return 0;
}
static void __exit fpe_exit(void)
{
thread_unregister_notifier(&nwfpe_notifier_block);
/* Restore the values we saved earlier. */
kern_fp_enter = orig_fp_enter;
fp_init = orig_fp_init;
}
/*

View File

@ -15,6 +15,8 @@
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <asm/thread_notify.h>
#include <asm/vfp.h>
#include "vfpinstr.h"
@ -36,37 +38,54 @@ union vfp_state *last_VFP_context;
*/
unsigned int VFP_arch;
/*
* Per-thread VFP initialisation.
*/
void vfp_flush_thread(union vfp_state *vfp)
static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
{
memset(vfp, 0, sizeof(union vfp_state));
struct thread_info *thread = v;
union vfp_state *vfp = &thread->vfpstate;
vfp->hard.fpexc = FPEXC_ENABLE;
vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
switch (cmd) {
case THREAD_NOTIFY_FLUSH:
/*
* Per-thread VFP initialisation.
*/
memset(vfp, 0, sizeof(union vfp_state));
/*
* Disable VFP to ensure we initialise it first.
*/
fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_ENABLE);
vfp->hard.fpexc = FPEXC_ENABLE;
vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
/*
* Ensure we don't try to overwrite our newly initialised
* state information on the first fault.
*/
if (last_VFP_context == vfp)
last_VFP_context = NULL;
/*
* Disable VFP to ensure we initialise it first.
*/
fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_ENABLE);
/*
* FALLTHROUGH: Ensure we don't try to overwrite our newly
* initialised state information on the first fault.
*/
case THREAD_NOTIFY_RELEASE:
/*
* Per-thread VFP cleanup.
*/
if (last_VFP_context == vfp)
last_VFP_context = NULL;
break;
case THREAD_NOTIFY_SWITCH:
/*
* Always disable VFP so we can lazily save/restore the
* old state.
*/
fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_ENABLE);
break;
}
return NOTIFY_DONE;
}
/*
* Per-thread VFP cleanup.
*/
void vfp_release_thread(union vfp_state *vfp)
{
if (last_VFP_context == vfp)
last_VFP_context = NULL;
}
static struct notifier_block vfp_notifier_block = {
.notifier_call = vfp_notifier,
};
/*
* Raise a SIGFPE for the current process.
@ -281,6 +300,8 @@ static int __init vfp_init(void)
(vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT,
(vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT);
vfp_vector = vfp_support_entry;
thread_register_notifier(&vfp_notifier_block);
}
return 0;
}

View File

@ -0,0 +1,48 @@
/*
* linux/include/asm-arm/thread_notify.h
*
* Copyright (C) 2006 Russell King.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef ASMARM_THREAD_NOTIFY_H
#define ASMARM_THREAD_NOTIFY_H
#ifdef __KERNEL__
#ifndef __ASSEMBLY__
#include <linux/notifier.h>
#include <asm/thread_info.h>
static inline int thread_register_notifier(struct notifier_block *n)
{
extern struct atomic_notifier_head thread_notify_head;
return atomic_notifier_chain_register(&thread_notify_head, n);
}
static inline void thread_unregister_notifier(struct notifier_block *n)
{
extern struct atomic_notifier_head thread_notify_head;
atomic_notifier_chain_unregister(&thread_notify_head, n);
}
static inline void thread_notify(unsigned long rc, struct thread_info *thread)
{
extern struct atomic_notifier_head thread_notify_head;
atomic_notifier_call_chain(&thread_notify_head, rc, thread);
}
#endif
/*
* These are the reason codes for the thread notifier.
*/
#define THREAD_NOTIFY_FLUSH 0
#define THREAD_NOTIFY_RELEASE 1
#define THREAD_NOTIFY_SWITCH 2
#endif
#endif