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3bd3706251
In commit:
4b53a3412d ("sched/core: Remove the tsk_nr_cpus_allowed() wrapper")
the tsk_nr_cpus_allowed() wrapper was removed. There was not
much difference in !RT but in RT we used this to implement
migrate_disable(). Within a migrate_disable() section the CPU mask is
restricted to single CPU while the "normal" CPU mask remains untouched.
As an alternative implementation Ingo suggested to use:
struct task_struct {
const cpumask_t *cpus_ptr;
cpumask_t cpus_mask;
};
with
t->cpus_ptr = &t->cpus_mask;
In -RT we then can switch the cpus_ptr to:
t->cpus_ptr = &cpumask_of(task_cpu(p));
in a migration disabled region. The rules are simple:
- Code that 'uses' ->cpus_allowed would use the pointer.
- Code that 'modifies' ->cpus_allowed would use the direct mask.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190423142636.14347-1-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
194 lines
5.3 KiB
C
194 lines
5.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/init_task.h>
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#include <linux/export.h>
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#include <linux/mqueue.h>
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#include <linux/sched.h>
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#include <linux/sched/sysctl.h>
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#include <linux/sched/rt.h>
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#include <linux/sched/task.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/audit.h>
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#include <linux/numa.h>
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#include <asm/pgtable.h>
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#include <linux/uaccess.h>
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static struct signal_struct init_signals = {
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.nr_threads = 1,
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.thread_head = LIST_HEAD_INIT(init_task.thread_node),
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.wait_chldexit = __WAIT_QUEUE_HEAD_INITIALIZER(init_signals.wait_chldexit),
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.shared_pending = {
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.list = LIST_HEAD_INIT(init_signals.shared_pending.list),
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.signal = {{0}}
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},
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.multiprocess = HLIST_HEAD_INIT,
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.rlim = INIT_RLIMITS,
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.cred_guard_mutex = __MUTEX_INITIALIZER(init_signals.cred_guard_mutex),
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#ifdef CONFIG_POSIX_TIMERS
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.posix_timers = LIST_HEAD_INIT(init_signals.posix_timers),
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.cputimer = {
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.cputime_atomic = INIT_CPUTIME_ATOMIC,
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.running = false,
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.checking_timer = false,
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},
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#endif
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INIT_CPU_TIMERS(init_signals)
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.pids = {
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[PIDTYPE_PID] = &init_struct_pid,
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[PIDTYPE_TGID] = &init_struct_pid,
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[PIDTYPE_PGID] = &init_struct_pid,
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[PIDTYPE_SID] = &init_struct_pid,
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},
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INIT_PREV_CPUTIME(init_signals)
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};
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static struct sighand_struct init_sighand = {
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.count = REFCOUNT_INIT(1),
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.action = { { { .sa_handler = SIG_DFL, } }, },
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.siglock = __SPIN_LOCK_UNLOCKED(init_sighand.siglock),
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.signalfd_wqh = __WAIT_QUEUE_HEAD_INITIALIZER(init_sighand.signalfd_wqh),
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};
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/*
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* Set up the first task table, touch at your own risk!. Base=0,
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* limit=0x1fffff (=2MB)
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*/
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struct task_struct init_task
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#ifdef CONFIG_ARCH_TASK_STRUCT_ON_STACK
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__init_task_data
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#endif
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= {
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#ifdef CONFIG_THREAD_INFO_IN_TASK
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.thread_info = INIT_THREAD_INFO(init_task),
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.stack_refcount = REFCOUNT_INIT(1),
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#endif
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.state = 0,
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.stack = init_stack,
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.usage = REFCOUNT_INIT(2),
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.flags = PF_KTHREAD,
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.prio = MAX_PRIO - 20,
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.static_prio = MAX_PRIO - 20,
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.normal_prio = MAX_PRIO - 20,
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.policy = SCHED_NORMAL,
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.cpus_ptr = &init_task.cpus_mask,
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.cpus_mask = CPU_MASK_ALL,
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.nr_cpus_allowed= NR_CPUS,
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.mm = NULL,
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.active_mm = &init_mm,
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.restart_block = {
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.fn = do_no_restart_syscall,
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},
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.se = {
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.group_node = LIST_HEAD_INIT(init_task.se.group_node),
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},
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.rt = {
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.run_list = LIST_HEAD_INIT(init_task.rt.run_list),
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.time_slice = RR_TIMESLICE,
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},
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.tasks = LIST_HEAD_INIT(init_task.tasks),
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#ifdef CONFIG_SMP
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.pushable_tasks = PLIST_NODE_INIT(init_task.pushable_tasks, MAX_PRIO),
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#endif
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#ifdef CONFIG_CGROUP_SCHED
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.sched_task_group = &root_task_group,
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#endif
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.ptraced = LIST_HEAD_INIT(init_task.ptraced),
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.ptrace_entry = LIST_HEAD_INIT(init_task.ptrace_entry),
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.real_parent = &init_task,
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.parent = &init_task,
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.children = LIST_HEAD_INIT(init_task.children),
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.sibling = LIST_HEAD_INIT(init_task.sibling),
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.group_leader = &init_task,
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RCU_POINTER_INITIALIZER(real_cred, &init_cred),
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RCU_POINTER_INITIALIZER(cred, &init_cred),
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.comm = INIT_TASK_COMM,
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.thread = INIT_THREAD,
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.fs = &init_fs,
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.files = &init_files,
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.signal = &init_signals,
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.sighand = &init_sighand,
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.nsproxy = &init_nsproxy,
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.pending = {
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.list = LIST_HEAD_INIT(init_task.pending.list),
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.signal = {{0}}
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},
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.blocked = {{0}},
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.alloc_lock = __SPIN_LOCK_UNLOCKED(init_task.alloc_lock),
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.journal_info = NULL,
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INIT_CPU_TIMERS(init_task)
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.pi_lock = __RAW_SPIN_LOCK_UNLOCKED(init_task.pi_lock),
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.timer_slack_ns = 50000, /* 50 usec default slack */
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.thread_pid = &init_struct_pid,
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.thread_group = LIST_HEAD_INIT(init_task.thread_group),
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.thread_node = LIST_HEAD_INIT(init_signals.thread_head),
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#ifdef CONFIG_AUDIT
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.loginuid = INVALID_UID,
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.sessionid = AUDIT_SID_UNSET,
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#endif
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#ifdef CONFIG_PERF_EVENTS
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.perf_event_mutex = __MUTEX_INITIALIZER(init_task.perf_event_mutex),
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.perf_event_list = LIST_HEAD_INIT(init_task.perf_event_list),
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#endif
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#ifdef CONFIG_PREEMPT_RCU
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.rcu_read_lock_nesting = 0,
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.rcu_read_unlock_special.s = 0,
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.rcu_node_entry = LIST_HEAD_INIT(init_task.rcu_node_entry),
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.rcu_blocked_node = NULL,
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#endif
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#ifdef CONFIG_TASKS_RCU
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.rcu_tasks_holdout = false,
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.rcu_tasks_holdout_list = LIST_HEAD_INIT(init_task.rcu_tasks_holdout_list),
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.rcu_tasks_idle_cpu = -1,
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#endif
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#ifdef CONFIG_CPUSETS
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.mems_allowed_seq = SEQCNT_ZERO(init_task.mems_allowed_seq),
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#endif
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#ifdef CONFIG_RT_MUTEXES
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.pi_waiters = RB_ROOT_CACHED,
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.pi_top_task = NULL,
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#endif
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INIT_PREV_CPUTIME(init_task)
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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.vtime.seqcount = SEQCNT_ZERO(init_task.vtime_seqcount),
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.vtime.starttime = 0,
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.vtime.state = VTIME_SYS,
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#endif
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#ifdef CONFIG_NUMA_BALANCING
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.numa_preferred_nid = NUMA_NO_NODE,
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.numa_group = NULL,
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.numa_faults = NULL,
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#endif
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#ifdef CONFIG_KASAN
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.kasan_depth = 1,
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#endif
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#ifdef CONFIG_TRACE_IRQFLAGS
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.softirqs_enabled = 1,
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#endif
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#ifdef CONFIG_LOCKDEP
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.lockdep_recursion = 0,
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#endif
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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.ret_stack = NULL,
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#endif
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#if defined(CONFIG_TRACING) && defined(CONFIG_PREEMPT)
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.trace_recursion = 0,
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#endif
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#ifdef CONFIG_LIVEPATCH
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.patch_state = KLP_UNDEFINED,
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#endif
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#ifdef CONFIG_SECURITY
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.security = NULL,
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#endif
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};
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EXPORT_SYMBOL(init_task);
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/*
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* Initial thread structure. Alignment of this is handled by a special
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* linker map entry.
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*/
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#ifndef CONFIG_THREAD_INFO_IN_TASK
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struct thread_info init_thread_info __init_thread_info = INIT_THREAD_INFO(init_task);
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#endif
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