8a102eed9c
Currently, to tell a task that it should go to the refrigerator, we set the PF_FREEZE flag for it and send a fake signal to it. Unfortunately there are two SMP-related problems with this approach. First, a task running on another CPU may be updating its flags while the freezer attempts to set PF_FREEZE for it and this may leave the task's flags in an inconsistent state. Second, there is a potential race between freeze_process() and refrigerator() in which freeze_process() running on one CPU is reading a task's PF_FREEZE flag while refrigerator() running on another CPU has just set PF_FROZEN for the same task and attempts to reset PF_FREEZE for it. If the refrigerator wins the race, freeze_process() will state that PF_FREEZE hasn't been set for the task and will set it unnecessarily, so the task will go to the refrigerator once again after it's been thawed. To solve first of these problems we need to stop using PF_FREEZE to tell tasks that they should go to the refrigerator. Instead, we can introduce a special TIF_*** flag and use it for this purpose, since it is allowed to change the other tasks' TIF_*** flags and there are special calls for it. To avoid the freeze_process()-refrigerator() race we can make freeze_process() to always check the task's PF_FROZEN flag after it's read its "freeze" flag. We should also make sure that refrigerator() will always reset the task's "freeze" flag after it's set PF_FROZEN for it. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Cc: Russell King <rmk@arm.linux.org.uk> Cc: David Howells <dhowells@redhat.com> Cc: Andi Kleen <ak@muc.de> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Paul Mundt <lethal@linux-sh.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
170 lines
5.1 KiB
C
170 lines
5.1 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_FREEZE 23 /* is freezing for suspend */
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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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#define _TIF_FREEZE (1<<TIF_FREEZE)
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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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