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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>
114 lines
4.2 KiB
C
114 lines
4.2 KiB
C
/*
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* Copyright (C) 2002-2003 Hewlett-Packard Co
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* David Mosberger-Tang <davidm@hpl.hp.com>
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*/
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#ifndef _ASM_IA64_THREAD_INFO_H
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#define _ASM_IA64_THREAD_INFO_H
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#ifndef ASM_OFFSETS_C
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#include <asm/asm-offsets.h>
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#endif
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#include <asm/processor.h>
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#include <asm/ptrace.h>
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#define PREEMPT_ACTIVE_BIT 30
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#define PREEMPT_ACTIVE (1 << PREEMPT_ACTIVE_BIT)
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#ifndef __ASSEMBLY__
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/*
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* On IA-64, we want to keep the task structure and kernel stack together, so they can be
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* mapped by a single TLB entry and so they can be addressed by the "current" pointer
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* without having to do pointer masking.
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*/
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struct thread_info {
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struct task_struct *task; /* XXX not really needed, except for dup_task_struct() */
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struct exec_domain *exec_domain;/* execution domain */
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__u32 flags; /* thread_info flags (see TIF_*) */
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__u32 cpu; /* current CPU */
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__u32 last_cpu; /* Last CPU thread ran on */
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__u32 status; /* Thread synchronous flags */
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mm_segment_t addr_limit; /* user-level address space limit */
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int preempt_count; /* 0=premptable, <0=BUG; will also serve as bh-counter */
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struct restart_block restart_block;
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};
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#define THREAD_SIZE KERNEL_STACK_SIZE
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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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.addr_limit = KERNEL_DS, \
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.preempt_count = 0, \
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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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#ifndef ASM_OFFSETS_C
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/* how to get the thread information struct from C */
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#define current_thread_info() ((struct thread_info *) ((char *) current + IA64_TASK_SIZE))
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#define alloc_thread_info(tsk) ((struct thread_info *) ((char *) (tsk) + IA64_TASK_SIZE))
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#define task_thread_info(tsk) ((struct thread_info *) ((char *) (tsk) + IA64_TASK_SIZE))
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#else
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#define current_thread_info() ((struct thread_info *) 0)
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#define alloc_thread_info(tsk) ((struct thread_info *) 0)
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#define task_thread_info(tsk) ((struct thread_info *) 0)
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#endif
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#define free_thread_info(ti) /* nothing */
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#define task_stack_page(tsk) ((void *)(tsk))
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#define __HAVE_THREAD_FUNCTIONS
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#define setup_thread_stack(p, org) \
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*task_thread_info(p) = *task_thread_info(org); \
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task_thread_info(p)->task = (p);
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#define end_of_stack(p) (unsigned long *)((void *)(p) + IA64_RBS_OFFSET)
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#define __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
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#define alloc_task_struct() ((struct task_struct *)__get_free_pages(GFP_KERNEL | __GFP_COMP, KERNEL_STACK_SIZE_ORDER))
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#define free_task_struct(tsk) free_pages((unsigned long) (tsk), KERNEL_STACK_SIZE_ORDER)
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#endif /* !__ASSEMBLY */
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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 least-significant 16 bits, other flags
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* in top 16 bits
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*/
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#define TIF_NOTIFY_RESUME 0 /* resumption notification requested */
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#define TIF_SIGPENDING 1 /* signal pending */
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#define TIF_NEED_RESCHED 2 /* rescheduling necessary */
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#define TIF_SYSCALL_TRACE 3 /* syscall trace active */
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#define TIF_SYSCALL_AUDIT 4 /* syscall auditing active */
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#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
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#define TIF_MEMDIE 17
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#define TIF_MCA_INIT 18 /* this task is processing MCA or INIT */
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#define TIF_DB_DISABLED 19 /* debug trap disabled for fsyscall */
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#define TIF_FREEZE 20 /* is freezing for suspend */
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#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
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#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
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#define _TIF_SYSCALL_TRACEAUDIT (_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT)
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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_NEED_RESCHED (1 << TIF_NEED_RESCHED)
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#define _TIF_POLLING_NRFLAG (1 << TIF_POLLING_NRFLAG)
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#define _TIF_MCA_INIT (1 << TIF_MCA_INIT)
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#define _TIF_DB_DISABLED (1 << TIF_DB_DISABLED)
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#define _TIF_FREEZE (1 << TIF_FREEZE)
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/* "work to do on user-return" bits */
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#define TIF_ALLWORK_MASK (_TIF_NOTIFY_RESUME|_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT)
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/* like TIF_ALLWORK_BITS but sans TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT */
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#define TIF_WORK_MASK (TIF_ALLWORK_MASK&~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT))
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#define TS_POLLING 1 /* 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 /* _ASM_IA64_THREAD_INFO_H */
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