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authorEric W. Biederman <ebiederm@xmission.com>2017-09-26 13:06:43 -0500
committerEric W. Biederman <ebiederm@xmission.com>2018-07-21 10:43:12 -0500
commit2c4704756cab7cfa031ada4dab361562f0e357c0 (patch)
tree8757eb8762d60e34eeab747493759abf3f902c09 /include/linux/sched.h
parent71dbc8a96953aa91c50181a526acb7f80af74f67 (diff)
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>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r--include/linux/sched.h22
1 files changed, 4 insertions, 18 deletions
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)