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[ARM] Add thread_notify infrastructure

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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>
This commit is contained in:
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
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24
arch/arm/kernel/entry-armv.S
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

2
arch/arm/kernel/iwmmxt.S
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

24
arch/arm/kernel/process.c
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
}

25
arch/arm/nwfpe/fpmodule.c
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;
}
/*

71
arch/arm/vfp/vfpmodule.c
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;
}

48
include/asm-arm/thread_notify.h Normal file
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