diff options
author | Eric W. Biederman <ebiederm@xmission.com> | 2017-09-26 21:06:43 +0300 |
---|---|---|
committer | Eric W. Biederman <ebiederm@xmission.com> | 2018-07-21 18:43:12 +0300 |
commit | 2c4704756cab7cfa031ada4dab361562f0e357c0 (patch) | |
tree | 8757eb8762d60e34eeab747493759abf3f902c09 | |
parent | 71dbc8a96953aa91c50181a526acb7f80af74f67 (diff) | |
download | linux-2c4704756cab7cfa031ada4dab361562f0e357c0.tar.xz |
pids: Move the pgrp and session pid pointers from task_struct to signal_struct
To access these fields the code always has to go to group leader so
going to signal struct is no loss and is actually a fundamental simplification.
This saves a little bit of memory by only allocating the pid pointer array
once instead of once for every thread, and even better this removes a
few potential races caused by the fact that group_leader can be changed
by de_thread, while signal_struct can not.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r-- | arch/ia64/kernel/asm-offsets.c | 2 | ||||
-rw-r--r-- | arch/ia64/kernel/fsys.S | 4 | ||||
-rw-r--r-- | fs/autofs/autofs_i.h | 1 | ||||
-rw-r--r-- | include/linux/init_task.h | 9 | ||||
-rw-r--r-- | include/linux/pid.h | 8 | ||||
-rw-r--r-- | include/linux/sched.h | 22 | ||||
-rw-r--r-- | include/linux/sched/signal.h | 26 | ||||
-rw-r--r-- | init/init_task.c | 11 | ||||
-rw-r--r-- | kernel/fork.c | 23 | ||||
-rw-r--r-- | kernel/pid.c | 45 |
10 files changed, 78 insertions, 73 deletions
diff --git a/arch/ia64/kernel/asm-offsets.c b/arch/ia64/kernel/asm-offsets.c index f5433bb7f04a..c1f8a57855af 100644 --- a/arch/ia64/kernel/asm-offsets.c +++ b/arch/ia64/kernel/asm-offsets.c @@ -50,7 +50,7 @@ void foo(void) DEFINE(IA64_TASK_BLOCKED_OFFSET,offsetof (struct task_struct, blocked)); DEFINE(IA64_TASK_CLEAR_CHILD_TID_OFFSET,offsetof (struct task_struct, clear_child_tid)); - DEFINE(IA64_TASK_TGIDLINK_OFFSET, offsetof (struct task_struct, pids[PIDTYPE_PID].pid)); + DEFINE(IA64_TASK_THREAD_PID_OFFSET,offsetof (struct task_struct, thread_pid)); DEFINE(IA64_PID_LEVEL_OFFSET, offsetof (struct pid, level)); DEFINE(IA64_PID_UPID_OFFSET, offsetof (struct pid, numbers[0])); DEFINE(IA64_TASK_PENDING_OFFSET,offsetof (struct task_struct, pending)); diff --git a/arch/ia64/kernel/fsys.S b/arch/ia64/kernel/fsys.S index eaf5a0d6f3e0..e85ebdac678b 100644 --- a/arch/ia64/kernel/fsys.S +++ b/arch/ia64/kernel/fsys.S @@ -96,11 +96,11 @@ ENTRY(fsys_set_tid_address) .altrp b6 .body add r9=TI_FLAGS+IA64_TASK_SIZE,r16 - add r17=IA64_TASK_TGIDLINK_OFFSET,r16 + add r17=IA64_TASK_THREAD_PID_OFFSET,r16 ;; ld4 r9=[r9] tnat.z p6,p7=r32 // check argument register for being NaT - ld8 r17=[r17] // r17 = current->pids[PIDTYPE_PID].pid + ld8 r17=[r17] // r17 = current->thread_pid ;; and r9=TIF_ALLWORK_MASK,r9 add r8=IA64_PID_LEVEL_OFFSET,r17 diff --git a/fs/autofs/autofs_i.h b/fs/autofs/autofs_i.h index 9400a9f6318a..502812289850 100644 --- a/fs/autofs/autofs_i.h +++ b/fs/autofs/autofs_i.h @@ -18,6 +18,7 @@ #include <linux/string.h> #include <linux/wait.h> #include <linux/sched.h> +#include <linux/sched/signal.h> #include <linux/mount.h> #include <linux/namei.h> #include <linux/uaccess.h> diff --git a/include/linux/init_task.h b/include/linux/init_task.h index a454b8aeb938..a7083a45a26c 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -46,15 +46,6 @@ extern struct cred init_cred; #define INIT_CPU_TIMERS(s) #endif -#define INIT_PID_LINK(type) \ -{ \ - .node = { \ - .next = NULL, \ - .pprev = NULL, \ - }, \ - .pid = &init_struct_pid, \ -} - #define INIT_TASK_COMM "swapper" /* Attach to the init_task data structure for proper alignment */ diff --git a/include/linux/pid.h b/include/linux/pid.h index 7633d55d9a24..3d4c504dcc8c 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -67,12 +67,6 @@ struct pid extern struct pid init_struct_pid; -struct pid_link -{ - struct hlist_node node; - struct pid *pid; -}; - static inline struct pid *get_pid(struct pid *pid) { if (pid) @@ -177,7 +171,7 @@ pid_t pid_vnr(struct pid *pid); do { \ if ((pid) != NULL) \ hlist_for_each_entry_rcu((task), \ - &(pid)->tasks[type], pids[type].node) { + &(pid)->tasks[type], pid_links[type]) { /* * Both old and new leaders may be attached to diff --git a/include/linux/sched.h b/include/linux/sched.h index a461ff89a3af..445bdf5b1f64 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -775,7 +775,8 @@ struct task_struct { struct list_head ptrace_entry; /* PID/PID hash table linkage. */ - struct pid_link pids[PIDTYPE_MAX]; + struct pid *thread_pid; + struct hlist_node pid_links[PIDTYPE_MAX]; struct list_head thread_group; struct list_head thread_node; @@ -1199,22 +1200,7 @@ struct task_struct { static inline struct pid *task_pid(struct task_struct *task) { - return task->pids[PIDTYPE_PID].pid; -} - -/* - * Without tasklist or RCU lock it is not safe to dereference - * the result of task_pgrp/task_session even if task == current, - * we can race with another thread doing sys_setsid/sys_setpgid. - */ -static inline struct pid *task_pgrp(struct task_struct *task) -{ - return task->group_leader->pids[PIDTYPE_PGID].pid; -} - -static inline struct pid *task_session(struct task_struct *task) -{ - return task->group_leader->pids[PIDTYPE_SID].pid; + return task->thread_pid; } /* @@ -1263,7 +1249,7 @@ static inline pid_t task_tgid_nr(struct task_struct *tsk) */ static inline int pid_alive(const struct task_struct *p) { - return p->pids[PIDTYPE_PID].pid != NULL; + return p->thread_pid != NULL; } static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index b95a272c1ab5..2dcded16eb1e 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -146,7 +146,9 @@ struct signal_struct { #endif + /* PID/PID hash table linkage. */ struct pid *leader_pid; + struct pid *pids[PIDTYPE_MAX]; #ifdef CONFIG_NO_HZ_FULL atomic_t tick_dep_mask; @@ -559,9 +561,12 @@ void walk_process_tree(struct task_struct *top, proc_visitor, void *); static inline struct pid *task_pid_type(struct task_struct *task, enum pid_type type) { - if (type != PIDTYPE_PID) - task = task->group_leader; - return task->pids[type].pid; + struct pid *pid; + if (type == PIDTYPE_PID) + pid = task_pid(task); + else + pid = task->signal->pids[type]; + return pid; } static inline struct pid *task_tgid(struct task_struct *task) @@ -569,6 +574,21 @@ static inline struct pid *task_tgid(struct task_struct *task) return task->signal->leader_pid; } +/* + * Without tasklist or RCU lock it is not safe to dereference + * the result of task_pgrp/task_session even if task == current, + * we can race with another thread doing sys_setsid/sys_setpgid. + */ +static inline struct pid *task_pgrp(struct task_struct *task) +{ + return task->signal->pids[PIDTYPE_PGID]; +} + +static inline struct pid *task_session(struct task_struct *task) +{ + return task->signal->pids[PIDTYPE_SID]; +} + static inline int get_nr_threads(struct task_struct *tsk) { return tsk->signal->nr_threads; diff --git a/init/init_task.c b/init/init_task.c index 7914ffb8dc73..db12a61259f1 100644 --- a/init/init_task.c +++ b/init/init_task.c @@ -34,6 +34,11 @@ static struct signal_struct init_signals = { #endif INIT_CPU_TIMERS(init_signals) .leader_pid = &init_struct_pid, + .pids = { + [PIDTYPE_PID] = &init_struct_pid, + [PIDTYPE_PGID] = &init_struct_pid, + [PIDTYPE_SID] = &init_struct_pid, + }, INIT_PREV_CPUTIME(init_signals) }; @@ -112,11 +117,7 @@ struct task_struct init_task INIT_CPU_TIMERS(init_task) .pi_lock = __RAW_SPIN_LOCK_UNLOCKED(init_task.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_pid = &init_struct_pid, .thread_group = LIST_HEAD_INIT(init_task.thread_group), .thread_node = LIST_HEAD_INIT(init_signals.thread_head), #ifdef CONFIG_AUDITSYSCALL diff --git a/kernel/fork.c b/kernel/fork.c index 9440d61b925c..d2952162399b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1549,10 +1549,22 @@ static void posix_cpu_timers_init(struct task_struct *tsk) static inline void posix_cpu_timers_init(struct task_struct *tsk) { } #endif +static inline void init_task_pid_links(struct task_struct *task) +{ + enum pid_type type; + + for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { + INIT_HLIST_NODE(&task->pid_links[type]); + } +} + static inline void init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) { - task->pids[type].pid = pid; + if (type == PIDTYPE_PID) + task->thread_pid = pid; + else + task->signal->pids[type] = pid; } static inline void rcu_copy_process(struct task_struct *p) @@ -1928,6 +1940,7 @@ static __latent_entropy struct task_struct *copy_process( goto bad_fork_cancel_cgroup; } + init_task_pid_links(p); if (likely(p->pid)) { ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace); @@ -2036,13 +2049,13 @@ fork_out: return ERR_PTR(retval); } -static inline void init_idle_pids(struct pid_link *links) +static inline void init_idle_pids(struct task_struct *idle) { enum pid_type type; for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) { - INIT_HLIST_NODE(&links[type].node); /* not really needed */ - links[type].pid = &init_struct_pid; + INIT_HLIST_NODE(&idle->pid_links[type]); /* not really needed */ + init_task_pid(idle, type, &init_struct_pid); } } @@ -2052,7 +2065,7 @@ struct task_struct *fork_idle(int cpu) task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0, 0, cpu_to_node(cpu)); if (!IS_ERR(task)) { - init_idle_pids(task->pids); + init_idle_pids(task); init_idle(task, cpu); } diff --git a/kernel/pid.c b/kernel/pid.c index d0de2b59f86f..f8486d2e2346 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -265,27 +265,35 @@ struct pid *find_vpid(int nr) } EXPORT_SYMBOL_GPL(find_vpid); +static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type) +{ + return (type == PIDTYPE_PID) ? + &task->thread_pid : + (type == __PIDTYPE_TGID) ? + &task->signal->leader_pid : + &task->signal->pids[type]; +} + /* * attach_pid() must be called with the tasklist_lock write-held. */ void attach_pid(struct task_struct *task, enum pid_type type) { - struct pid_link *link = &task->pids[type]; - hlist_add_head_rcu(&link->node, &link->pid->tasks[type]); + struct pid *pid = *task_pid_ptr(task, type); + hlist_add_head_rcu(&task->pid_links[type], &pid->tasks[type]); } static void __change_pid(struct task_struct *task, enum pid_type type, struct pid *new) { - struct pid_link *link; + struct pid **pid_ptr = task_pid_ptr(task, type); struct pid *pid; int tmp; - link = &task->pids[type]; - pid = link->pid; + pid = *pid_ptr; - hlist_del_rcu(&link->node); - link->pid = new; + hlist_del_rcu(&task->pid_links[type]); + *pid_ptr = new; for (tmp = PIDTYPE_MAX; --tmp >= 0; ) if (!hlist_empty(&pid->tasks[tmp])) @@ -310,8 +318,9 @@ void change_pid(struct task_struct *task, enum pid_type type, void transfer_pid(struct task_struct *old, struct task_struct *new, enum pid_type type) { - new->pids[type].pid = old->pids[type].pid; - hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node); + if (type == PIDTYPE_PID) + new->thread_pid = old->thread_pid; + hlist_replace_rcu(&old->pid_links[type], &new->pid_links[type]); } struct task_struct *pid_task(struct pid *pid, enum pid_type type) @@ -322,7 +331,7 @@ struct task_struct *pid_task(struct pid *pid, enum pid_type type) first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]), lockdep_tasklist_lock_is_held()); if (first) - result = hlist_entry(first, struct task_struct, pids[(type)].node); + result = hlist_entry(first, struct task_struct, pid_links[(type)]); } return result; } @@ -360,9 +369,7 @@ struct pid *get_task_pid(struct task_struct *task, enum pid_type type) { struct pid *pid; rcu_read_lock(); - if (type != PIDTYPE_PID) - task = task->group_leader; - pid = get_pid(rcu_dereference(task->pids[type].pid)); + pid = get_pid(rcu_dereference(*task_pid_ptr(task, type))); rcu_read_unlock(); return pid; } @@ -420,16 +427,8 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, rcu_read_lock(); if (!ns) ns = task_active_pid_ns(current); - if (likely(pid_alive(task))) { - struct pid *pid; - if (type == PIDTYPE_PID) - pid = task_pid(task); - else if (type == __PIDTYPE_TGID) - pid = task_tgid(task); - else - pid = rcu_dereference(task->group_leader->pids[type].pid); - nr = pid_nr_ns(pid, ns); - } + if (likely(pid_alive(task))) + nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns); rcu_read_unlock(); return nr; |