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0c740d0afc
kernel-ark/include/linux/init_task.h
Oleg Nesterov 0c740d0afc introduce for_each_thread() to replace the buggy while_each_thread() 
while_each_thread() and next_thread() should die, almost every lockless
usage is wrong.

1. Unless g == current, the lockless while_each_thread() is not safe.

   while_each_thread(g, t) can loop forever if g exits, next_thread()
   can't reach the unhashed thread in this case. Note that this can
   happen even if g is the group leader, it can exec.

2. Even if while_each_thread() itself was correct, people often use
   it wrongly.

   It was never safe to just take rcu_read_lock() and loop unless
   you verify that pid_alive(g) == T, even the first next_thread()
   can point to the already freed/reused memory.

This patch adds signal_struct->thread_head and task->thread_node to
create the normal rcu-safe list with the stable head.  The new
for_each_thread(g, t) helper is always safe under rcu_read_lock() as
long as this task_struct can't go away.

Note: of course it is ugly to have both task_struct->thread_node and the
old task_struct->thread_group, we will kill it later, after we change
the users of while_each_thread() to use for_each_thread().

Perhaps we can kill it even before we convert all users, we can
reimplement next_thread(t) using the new thread_head/thread_node.  But
we can't do this right now because this will lead to subtle behavioural
changes.  For example, do/while_each_thread() always sees at least one
task, while for_each_thread() can do nothing if the whole thread group
has died.  Or thread_group_empty(), currently its semantics is not clear
unless thread_group_leader(p) and we need to audit the callers before we
can change it.

So this patch adds the new interface which has to coexist with the old
one for some time, hopefully the next changes will be more or less
straightforward and the old one will go away soon.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Sergey Dyasly <dserrg@gmail.com>
Tested-by: Sergey Dyasly <dserrg@gmail.com>
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mandeep Singh Baines <msb@chromium.org>
Cc: "Ma, Xindong" <xindong.ma@intel.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: "Tu, Xiaobing" <xiaobing.tu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-01-21 16:19:46 -08:00

252 lines
6.6 KiB
C
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#ifndef _LINUX__INIT_TASK_H
#define _LINUX__INIT_TASK_H
#include <linux/rcupdate.h>
#include <linux/irqflags.h>
#include <linux/utsname.h>
#include <linux/lockdep.h>
#include <linux/ftrace.h>
#include <linux/ipc.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/securebits.h>
#include <linux/seqlock.h>
#include <linux/rbtree.h>
#include <net/net_namespace.h>
#include <linux/sched/rt.h>
#ifdef CONFIG_SMP
# define INIT_PUSHABLE_TASKS(tsk) \
.pushable_tasks = PLIST_NODE_INIT(tsk.pushable_tasks, MAX_PRIO),
#else
# define INIT_PUSHABLE_TASKS(tsk)
#endif
extern struct files_struct init_files;
extern struct fs_struct init_fs;
#ifdef CONFIG_CGROUPS
#define INIT_GROUP_RWSEM(sig) \
.group_rwsem = __RWSEM_INITIALIZER(sig.group_rwsem),
#else
#define INIT_GROUP_RWSEM(sig)
#endif
#ifdef CONFIG_CPUSETS
#define INIT_CPUSET_SEQ(tsk) \
.mems_allowed_seq = SEQCNT_ZERO(tsk.mems_allowed_seq),
#else
#define INIT_CPUSET_SEQ(tsk)
#endif
#define INIT_SIGNALS(sig) { \
.nr_threads = 1, \
.thread_head = LIST_HEAD_INIT(init_task.thread_node), \
.wait_chldexit = __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),\
.shared_pending = { \
.list = LIST_HEAD_INIT(sig.shared_pending.list), \
.signal = {{0}}}, \
.posix_timers = LIST_HEAD_INIT(sig.posix_timers), \
.cpu_timers = INIT_CPU_TIMERS(sig.cpu_timers), \
.rlim = INIT_RLIMITS, \
.cputimer = { \
.cputime = INIT_CPUTIME, \
.running = 0, \
.lock = __RAW_SPIN_LOCK_UNLOCKED(sig.cputimer.lock), \
}, \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(sig.cred_guard_mutex), \
INIT_GROUP_RWSEM(sig) \
}
extern struct nsproxy init_nsproxy;
#define INIT_SIGHAND(sighand) { \
.count = ATOMIC_INIT(1), \
.action = { { { .sa_handler = SIG_DFL, } }, }, \
.siglock = __SPIN_LOCK_UNLOCKED(sighand.siglock), \
.signalfd_wqh = __WAIT_QUEUE_HEAD_INITIALIZER(sighand.signalfd_wqh), \
}
extern struct group_info init_groups;
#define INIT_STRUCT_PID { \
.count = ATOMIC_INIT(1), \
.tasks = { \
{ .first = NULL }, \
{ .first = NULL }, \
{ .first = NULL }, \
}, \
.level = 0, \
.numbers = { { \
.nr = 0, \
.ns = &init_pid_ns, \
.pid_chain = { .next = NULL, .pprev = NULL }, \
}, } \
}
#define INIT_PID_LINK(type) \
{ \
.node = { \
.next = NULL, \
.pprev = NULL, \
}, \
.pid = &init_struct_pid, \
}
#ifdef CONFIG_AUDITSYSCALL
#define INIT_IDS \
.loginuid = INVALID_UID, \
.sessionid = -1,
#else
#define INIT_IDS
#endif
#ifdef CONFIG_RCU_BOOST
#define INIT_TASK_RCU_BOOST() \
.rcu_boost_mutex = NULL,
#else
#define INIT_TASK_RCU_BOOST()
#endif
#ifdef CONFIG_TREE_PREEMPT_RCU
#define INIT_TASK_RCU_TREE_PREEMPT() \
.rcu_blocked_node = NULL,
#else
#define INIT_TASK_RCU_TREE_PREEMPT(tsk)
#endif
#ifdef CONFIG_PREEMPT_RCU
#define INIT_TASK_RCU_PREEMPT(tsk) \
.rcu_read_lock_nesting = 0, \
.rcu_read_unlock_special = 0, \
.rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry), \
INIT_TASK_RCU_TREE_PREEMPT() \
INIT_TASK_RCU_BOOST()
#else
#define INIT_TASK_RCU_PREEMPT(tsk)
#endif
extern struct cred init_cred;
extern struct task_group root_task_group;
#ifdef CONFIG_CGROUP_SCHED
# define INIT_CGROUP_SCHED(tsk) \
.sched_task_group = &root_task_group,
#else
# define INIT_CGROUP_SCHED(tsk)
#endif
#ifdef CONFIG_PERF_EVENTS
# define INIT_PERF_EVENTS(tsk) \
.perf_event_mutex = \
__MUTEX_INITIALIZER(tsk.perf_event_mutex), \
.perf_event_list = LIST_HEAD_INIT(tsk.perf_event_list),
#else
# define INIT_PERF_EVENTS(tsk)
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
# define INIT_VTIME(tsk) \
.vtime_seqlock = __SEQLOCK_UNLOCKED(tsk.vtime_seqlock), \
.vtime_snap = 0, \
.vtime_snap_whence = VTIME_SYS,
#else
# define INIT_VTIME(tsk)
#endif
#define INIT_TASK_COMM "swapper"
#ifdef CONFIG_RT_MUTEXES
# define INIT_RT_MUTEXES(tsk) \
.pi_waiters = RB_ROOT, \
.pi_waiters_leftmost = NULL,
#else
# define INIT_RT_MUTEXES(tsk)
#endif
/*
* INIT_TASK is used to set up the first task table, touch at
* your own risk!. Base=0, limit=0x1fffff (=2MB)
*/
#define INIT_TASK(tsk) \
{ \
.state = 0, \
.stack = &init_thread_info, \
.usage = ATOMIC_INIT(2), \
.flags = PF_KTHREAD, \
.prio = MAX_PRIO-20, \
.static_prio = MAX_PRIO-20, \
.normal_prio = MAX_PRIO-20, \
.policy = SCHED_NORMAL, \
.cpus_allowed = CPU_MASK_ALL, \
.nr_cpus_allowed= NR_CPUS, \
.mm = NULL, \
.active_mm = &init_mm, \
.se = { \
.group_node = LIST_HEAD_INIT(tsk.se.group_node), \
}, \
.rt = { \
.run_list = LIST_HEAD_INIT(tsk.rt.run_list), \
.time_slice = RR_TIMESLICE, \
}, \
.tasks = LIST_HEAD_INIT(tsk.tasks), \
INIT_PUSHABLE_TASKS(tsk) \
INIT_CGROUP_SCHED(tsk) \
.ptraced = LIST_HEAD_INIT(tsk.ptraced), \
.ptrace_entry = LIST_HEAD_INIT(tsk.ptrace_entry), \
.real_parent = &tsk, \
.parent = &tsk, \
.children = LIST_HEAD_INIT(tsk.children), \
.sibling = LIST_HEAD_INIT(tsk.sibling), \
.group_leader = &tsk, \
RCU_POINTER_INITIALIZER(real_cred, &init_cred), \
RCU_POINTER_INITIALIZER(cred, &init_cred), \
.comm = INIT_TASK_COMM, \
.thread = INIT_THREAD, \
.fs = &init_fs, \
.files = &init_files, \
.signal = &init_signals, \
.sighand = &init_sighand, \
.nsproxy = &init_nsproxy, \
.pending = { \
.list = LIST_HEAD_INIT(tsk.pending.list), \
.signal = {{0}}}, \
.blocked = {{0}}, \
.alloc_lock = __SPIN_LOCK_UNLOCKED(tsk.alloc_lock), \
.journal_info = NULL, \
.cpu_timers = INIT_CPU_TIMERS(tsk.cpu_timers), \
.pi_lock = __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock), \
.timer_slack_ns = 50000, /* 50 usec default slack */ \
.pids = { \
[PIDTYPE_PID] = INIT_PID_LINK(PIDTYPE_PID), \
[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID), \
[PIDTYPE_SID] = INIT_PID_LINK(PIDTYPE_SID), \
}, \
.thread_group = LIST_HEAD_INIT(tsk.thread_group), \
.thread_node = LIST_HEAD_INIT(init_signals.thread_head), \
INIT_IDS \
INIT_PERF_EVENTS(tsk) \
INIT_TRACE_IRQFLAGS \
INIT_LOCKDEP \
INIT_FTRACE_GRAPH \
INIT_TRACE_RECURSION \
INIT_TASK_RCU_PREEMPT(tsk) \
INIT_CPUSET_SEQ(tsk) \
INIT_RT_MUTEXES(tsk) \
INIT_VTIME(tsk) \
}
#define INIT_CPU_TIMERS(cpu_timers) \
{ \
LIST_HEAD_INIT(cpu_timers[0]), \
LIST_HEAD_INIT(cpu_timers[1]), \
LIST_HEAD_INIT(cpu_timers[2]), \
}
/* Attach to the init_task data structure for proper alignment */
#define __init_task_data __attribute__((__section__(".data..init_task")))
#endif
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