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linux/include/asm-arm/thread_info.h
Paul Gortmaker 122214428a [ARM] 3911/2: Simplify alloc_thread_info on ARM 
Remove ARM local cache of 4 struct thread_info.
Can cause oops under certain circumstances.

Russell indicated the original optimization was
required on older kernels to avoid thread starvation
on memory fragmentation, but may no longer be
required.  I've updated the patch to 19rc4 and
ensured no <config.h> dain-bramage slipped in this
time (sorry about that).

Original description follows:

I was given some test results which pointed to an
Oops in alloc_thread_info (happened 2x), and after
looking at the code, I see that ARM has its own
local cache of 4 struct thread_info. There wasn't
any clear (to me) synchronization between the
alloc_thread_info and the free_thread_info.

I looked over the other arch, and they all simply
allocate them on an as needed basis, so I simplified
the ARM to do the same, based on the other arch
(e.g. PPC) and the folks doing the testing have
indicated that this fixed the oops.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2006-11-30 15:27:03 +00:00

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/*
* linux/include/asm-arm/thread_info.h
*
* Copyright (C) 2002 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 __ASM_ARM_THREAD_INFO_H
#define __ASM_ARM_THREAD_INFO_H
#ifdef __KERNEL__
#include <linux/compiler.h>
#include <asm/fpstate.h>
#define THREAD_SIZE_ORDER 1
#define THREAD_SIZE 8192
#define THREAD_START_SP (THREAD_SIZE - 8)
#ifndef __ASSEMBLY__
struct task_struct;
struct exec_domain;
#include <asm/ptrace.h>
#include <asm/types.h>
#include <asm/domain.h>
typedef unsigned long mm_segment_t;
struct cpu_context_save {
__u32 r4;
__u32 r5;
__u32 r6;
__u32 r7;
__u32 r8;
__u32 r9;
__u32 sl;
__u32 fp;
__u32 sp;
__u32 pc;
__u32 extra[2]; /* Xscale 'acc' register, etc */
};
/*
* low level task data that entry.S needs immediate access to.
* __switch_to() assumes cpu_context follows immediately after cpu_domain.
*/
struct thread_info {
unsigned long flags; /* low level flags */
int preempt_count; /* 0 => preemptable, <0 => bug */
mm_segment_t addr_limit; /* address limit */
struct task_struct *task; /* main task structure */
struct exec_domain *exec_domain; /* execution domain */
__u32 cpu; /* cpu */
__u32 cpu_domain; /* cpu domain */
struct cpu_context_save cpu_context; /* cpu context */
__u8 used_cp[16]; /* thread used copro */
unsigned long tp_value;
struct crunch_state crunchstate;
union fp_state fpstate __attribute__((aligned(8)));
union vfp_state vfpstate;
struct restart_block restart_block;
};
#define INIT_THREAD_INFO(tsk) \
{ \
.task = &tsk, \
.exec_domain = &default_exec_domain, \
.flags = 0, \
.preempt_count = 1, \
.addr_limit = KERNEL_DS, \
.cpu_domain = domain_val(DOMAIN_USER, DOMAIN_MANAGER) | \
domain_val(DOMAIN_KERNEL, DOMAIN_MANAGER) | \
domain_val(DOMAIN_IO, DOMAIN_CLIENT), \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
}
#define init_thread_info (init_thread_union.thread_info)
#define init_stack (init_thread_union.stack)
/*
* how to get the thread information struct from C
*/
static inline struct thread_info *current_thread_info(void) __attribute_const__;
static inline struct thread_info *current_thread_info(void)
{
register unsigned long sp asm ("sp");
return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
}
/* thread information allocation */
#ifdef CONFIG_DEBUG_STACK_USAGE
#define alloc_thread_info(tsk) \
((struct thread_info *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, \
THREAD_SIZE_ORDER))
#else
#define alloc_thread_info(tsk) \
((struct thread_info *)__get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER))
#endif
#define free_thread_info(info) \
free_pages((unsigned long)info, THREAD_SIZE_ORDER);
#define thread_saved_pc(tsk) \
((unsigned long)(pc_pointer(task_thread_info(tsk)->cpu_context.pc)))
#define thread_saved_fp(tsk) \
((unsigned long)(task_thread_info(tsk)->cpu_context.fp))
extern void crunch_task_disable(struct thread_info *);
extern void crunch_task_copy(struct thread_info *, void *);
extern void crunch_task_restore(struct thread_info *, void *);
extern void crunch_task_release(struct thread_info *);
extern void iwmmxt_task_disable(struct thread_info *);
extern void iwmmxt_task_copy(struct thread_info *, void *);
extern void iwmmxt_task_restore(struct thread_info *, void *);
extern void iwmmxt_task_release(struct thread_info *);
extern void iwmmxt_task_switch(struct thread_info *);
#endif
/*
* We use bit 30 of the preempt_count to indicate that kernel
* preemption is occurring. See include/asm-arm/hardirq.h.
*/
#define PREEMPT_ACTIVE 0x40000000
/*
* thread information flags:
* TIF_SYSCALL_TRACE - syscall trace active
* TIF_NOTIFY_RESUME - resumption notification requested
* TIF_SIGPENDING - signal pending
* TIF_NEED_RESCHED - rescheduling necessary
* TIF_USEDFPU - FPU was used by this task this quantum (SMP)
* TIF_POLLING_NRFLAG - true if poll_idle() is polling TIF_NEED_RESCHED
*/
#define TIF_NOTIFY_RESUME 0
#define TIF_SIGPENDING 1
#define TIF_NEED_RESCHED 2
#define TIF_SYSCALL_TRACE 8
#define TIF_POLLING_NRFLAG 16
#define TIF_USING_IWMMXT 17
#define TIF_MEMDIE 18
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
#define _TIF_USING_IWMMXT (1 << TIF_USING_IWMMXT)
/*
* Change these and you break ASM code in entry-common.S
*/
#define _TIF_WORK_MASK 0x000000ff
#endif /* __KERNEL__ */
#endif /* __ASM_ARM_THREAD_INFO_H */
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