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>
126 lines
3.5 KiB
C
126 lines
3.5 KiB
C
#ifndef __ASM_SH_THREAD_INFO_H
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#define __ASM_SH_THREAD_INFO_H
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/* SuperH version
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* Copyright (C) 2002 Niibe Yutaka
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*
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* The copyright of original i386 version is:
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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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#ifdef __KERNEL__
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#include <asm/page.h>
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#ifndef __ASSEMBLY__
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#include <asm/processor.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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unsigned long flags; /* low level flags */
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__u32 cpu;
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int preempt_count; /* 0 => preemptable, <0 => BUG */
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mm_segment_t addr_limit; /* thread address space */
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struct restart_block restart_block;
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unsigned long previous_sp; /* sp of previous stack in case
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of nested IRQ stacks */
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__u8 supervisor_stack[0];
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};
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#endif
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#define PREEMPT_ACTIVE 0x10000000
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#ifdef CONFIG_4KSTACKS
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#define THREAD_SIZE (PAGE_SIZE)
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#else
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#define THREAD_SIZE (PAGE_SIZE * 2)
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#endif
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#define STACK_WARN (THREAD_SIZE / 8)
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/*
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* macros/functions for gaining access to the thread information structure
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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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/* how to get the current stack pointer from C */
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register unsigned long current_stack_pointer asm("r15") __attribute_used__;
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/* how to get the thread information struct from C */
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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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#ifdef CONFIG_CPU_HAS_SR_RB
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__asm__("stc r7_bank, %0" : "=r" (ti));
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#else
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unsigned long __dummy;
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__asm__ __volatile__ (
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"mov r15, %0\n\t"
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"and %1, %0\n\t"
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: "=&r" (ti), "=r" (__dummy)
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: "1" (~(THREAD_SIZE - 1))
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: "memory");
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#endif
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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(ti) kzalloc(THREAD_SIZE, GFP_KERNEL)
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#else
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#define alloc_thread_info(ti) kmalloc(THREAD_SIZE, GFP_KERNEL)
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#endif
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#define free_thread_info(ti) kfree(ti)
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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 LSW
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* - other flags in MSW
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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_RESTORE_SIGMASK 4 /* restore signal mask in do_signal() */
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#define TIF_USEDFPU 16 /* FPU was used by this task this quantum (SMP) */
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#define TIF_POLLING_NRFLAG 17 /* true if poll_idle() is polling TIF_NEED_RESCHED */
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#define TIF_MEMDIE 18
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#define TIF_FREEZE 19
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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_NEED_RESCHED (1<<TIF_NEED_RESCHED)
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#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
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#define _TIF_USEDFPU (1<<TIF_USEDFPU)
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#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
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#define _TIF_FREEZE (1<<TIF_FREEZE)
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#define _TIF_WORK_MASK 0x000000FE /* work to do on interrupt/exception return */
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#define _TIF_ALLWORK_MASK 0x000000FF /* work to do on any return to u-space */
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#endif /* __KERNEL__ */
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#endif /* __ASM_SH_THREAD_INFO_H */
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