d3a4f48d48
Hello, Following my discussion with Andi. Here is a patch that introduces two new TIF flags to simplify the context switch code in __switch_to(). The idea is to minimize the number of cache lines accessed in the common case, i.e., when neither the debug registers nor the I/O bitmap are used. This patch covers the x86-64 modifications. A patch for i386 follows. Changelog: - 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 <signed-off-by>: eranian@hpl.hp.com Signed-off-by: Andi Kleen <ak@suse.de>
167 lines
5 KiB
C
167 lines
5 KiB
C
/* thread_info.h: x86_64 low-level thread information
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*
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* Copyright (C) 2002 David Howells (dhowells@redhat.com)
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* - Incorporating suggestions made by Linus Torvalds and Dave Miller
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*/
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#ifndef _ASM_THREAD_INFO_H
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#define _ASM_THREAD_INFO_H
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#ifdef __KERNEL__
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#include <asm/page.h>
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#include <asm/types.h>
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#include <asm/pda.h>
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/*
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* low level task data that entry.S needs immediate access to
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* - this struct should fit entirely inside of one cache line
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* - this struct shares the supervisor stack pages
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*/
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#ifndef __ASSEMBLY__
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struct task_struct;
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struct exec_domain;
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#include <asm/mmsegment.h>
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struct thread_info {
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struct task_struct *task; /* main task structure */
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struct exec_domain *exec_domain; /* execution domain */
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__u32 flags; /* low level flags */
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__u32 status; /* thread synchronous flags */
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__u32 cpu; /* current CPU */
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int preempt_count; /* 0 => preemptable, <0 => BUG */
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mm_segment_t addr_limit;
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struct restart_block restart_block;
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};
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#endif
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/*
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* macros/functions for gaining access to the thread information structure
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* preempt_count needs to be 1 initially, until the scheduler is functional.
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*/
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#ifndef __ASSEMBLY__
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#define INIT_THREAD_INFO(tsk) \
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{ \
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.task = &tsk, \
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.exec_domain = &default_exec_domain, \
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.flags = 0, \
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.cpu = 0, \
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.preempt_count = 1, \
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.addr_limit = KERNEL_DS, \
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.restart_block = { \
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.fn = do_no_restart_syscall, \
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}, \
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}
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#define init_thread_info (init_thread_union.thread_info)
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#define init_stack (init_thread_union.stack)
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static inline struct thread_info *current_thread_info(void)
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{
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struct thread_info *ti;
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ti = (void *)(read_pda(kernelstack) + PDA_STACKOFFSET - THREAD_SIZE);
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return ti;
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}
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/* do not use in interrupt context */
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static inline struct thread_info *stack_thread_info(void)
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{
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struct thread_info *ti;
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__asm__("andq %%rsp,%0; ":"=r" (ti) : "0" (~(THREAD_SIZE - 1)));
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return ti;
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}
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/* thread information allocation */
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#ifdef CONFIG_DEBUG_STACK_USAGE
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#define alloc_thread_info(tsk) \
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({ \
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struct thread_info *ret; \
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\
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ret = ((struct thread_info *) __get_free_pages(GFP_KERNEL,THREAD_ORDER)); \
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if (ret) \
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memset(ret, 0, THREAD_SIZE); \
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ret; \
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})
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#else
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#define alloc_thread_info(tsk) \
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((struct thread_info *) __get_free_pages(GFP_KERNEL,THREAD_ORDER))
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#endif
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#define free_thread_info(ti) free_pages((unsigned long) (ti), THREAD_ORDER)
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#else /* !__ASSEMBLY__ */
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/* how to get the thread information struct from ASM */
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#define GET_THREAD_INFO(reg) \
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movq %gs:pda_kernelstack,reg ; \
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subq $(THREAD_SIZE-PDA_STACKOFFSET),reg
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#endif
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/*
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* thread information flags
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* - these are process state flags that various assembly files may need to access
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* - pending work-to-be-done flags are in LSW
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* - other flags in MSW
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* Warning: layout of LSW is hardcoded in entry.S
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*/
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#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
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#define TIF_NOTIFY_RESUME 1 /* resumption notification requested */
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#define TIF_SIGPENDING 2 /* signal pending */
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#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
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#define TIF_SINGLESTEP 4 /* reenable singlestep on user return*/
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#define TIF_IRET 5 /* force IRET */
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#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
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#define TIF_SECCOMP 8 /* secure computing */
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#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */
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/* 16 free */
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#define TIF_IA32 17 /* 32bit process */
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#define TIF_FORK 18 /* ret_from_fork */
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#define TIF_ABI_PENDING 19
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#define TIF_MEMDIE 20
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#define TIF_DEBUG 21 /* uses debug registers */
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#define TIF_IO_BITMAP 22 /* uses I/O bitmap */
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#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
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#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
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#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
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#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
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#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
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#define _TIF_IRET (1<<TIF_IRET)
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#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
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#define _TIF_SECCOMP (1<<TIF_SECCOMP)
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#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
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#define _TIF_IA32 (1<<TIF_IA32)
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#define _TIF_FORK (1<<TIF_FORK)
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#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
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#define _TIF_DEBUG (1<<TIF_DEBUG)
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#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
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/* work to do on interrupt/exception return */
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#define _TIF_WORK_MASK \
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(0x0000FFFF & ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP|_TIF_SECCOMP))
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/* work to do on any return to user space */
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#define _TIF_ALLWORK_MASK (0x0000FFFF & ~_TIF_SECCOMP)
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/* flags to check in __switch_to() */
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#define _TIF_WORK_CTXSW (_TIF_DEBUG|_TIF_IO_BITMAP)
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#define PREEMPT_ACTIVE 0x10000000
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/*
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* Thread-synchronous status.
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*
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* This is different from the flags in that nobody else
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* ever touches our thread-synchronous status, so we don't
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* have to worry about atomic accesses.
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*/
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#define TS_USEDFPU 0x0001 /* FPU was used by this task this quantum (SMP) */
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#define TS_COMPAT 0x0002 /* 32bit syscall active */
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#define TS_POLLING 0x0004 /* true if in idle loop and not sleeping */
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#define tsk_is_polling(t) ((t)->thread_info->status & TS_POLLING)
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#endif /* __KERNEL__ */
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#endif /* _ASM_THREAD_INFO_H */
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