trivial - constify sched.h

Add const to some struct task_struct * uses

Signed-off-by Joe Perches <[email protected]>

---

 include/linux/sched.h |   24 ++++++++++++------------
 1 files changed, 12 insertions(+), 12 deletions(-)

include/linux/sched.h +12 -12

index ba78807..71d40a1 100644
@@ -1222,22 +1222,22 @@ static inline int rt_prio(int prio)
 	return 0;
 }
 
-static inline int rt_task(struct task_struct *p)
+static inline int rt_task(const struct task_struct *p)
 {
 	return rt_prio(p->prio);
 }
 
-static inline pid_t process_group(struct task_struct *tsk)
+static inline pid_t process_group(const struct task_struct *tsk)
 {
 	return tsk->signal->pgrp;
 }
 
-static inline pid_t signal_session(struct signal_struct *sig)
+static inline pid_t signal_session(const struct signal_struct *sig)
 {
 	return sig->__session;
 }
 
-static inline pid_t process_session(struct task_struct *tsk)
+static inline pid_t process_session(const struct task_struct *tsk)
 {
 	return signal_session(tsk->signal);
 }

@@ -1247,22 +1247,22 @@ static inline void set_signal_session(struct signal_struct *sig, pid_t session)
 	sig->__session = session;
 }
 
-static inline struct pid *task_pid(struct task_struct *task)
+static inline struct pid *task_pid(const struct task_struct *task)
 {
 	return task->pids[PIDTYPE_PID].pid;
 }
 
-static inline struct pid *task_tgid(struct task_struct *task)
+static inline struct pid *task_tgid(const struct task_struct *task)
 {
 	return task->group_leader->pids[PIDTYPE_PID].pid;
 }
 
-static inline struct pid *task_pgrp(struct task_struct *task)
+static inline struct pid *task_pgrp(const struct task_struct *task)
 {
 	return task->group_leader->pids[PIDTYPE_PGID].pid;
 }
 
-static inline struct pid *task_session(struct task_struct *task)
+static inline struct pid *task_session(const struct task_struct *task)
 {
 	return task->group_leader->pids[PIDTYPE_SID].pid;
 }

@@ -1275,7 +1275,7 @@ static inline struct pid *task_session(struct task_struct *task)
  * If pid_alive fails, then pointers within the task structure
  * can be stale and must not be dereferenced.
  */
-static inline int pid_alive(struct task_struct *p)
+static inline int pid_alive(const struct task_struct *p)
 {
 	return p->pids[PIDTYPE_PID].pid != NULL;
 }

@@ -1286,7 +1286,7 @@ static inline int pid_alive(struct task_struct *p)
  *
  * Check if a task structure is the first user space task the kernel created.
  */
-static inline int is_init(struct task_struct *tsk)
+static inline int is_init(const struct task_struct *tsk)
 {
 	return tsk->pid = 1;
 }

@@ -1639,7 +1639,7 @@ extern void wait_task_inactive(struct task_struct * p);
  * all we care about is that we have a task with the appropriate
  * pid, we don't actually care if we have the right task.
  */
-static inline int has_group_leader_pid(struct task_struct *p)
+static inline int has_group_leader_pid(const struct task_struct *p)
 {
 	return p->pid = p->tgid;
 }

@@ -1650,7 +1650,7 @@ static inline struct task_struct *next_thread(const struct task_struct *p)
 			  struct task_struct, thread_group);
 }
 
-static inline int thread_group_empty(struct task_struct *p)
+static inline int thread_group_empty(const struct task_struct *p)
 {
 	return list_empty(&p->thread_group);
 }

Add const to some struct task_struct * uses

Quoted 1 line · Joe Perches

Add const to some struct task_struct * uses

Why, oh, why?

Quoted 5 lines · Alexey Dobriyan

Quoted 1 line · Joe Perches

Add const to some struct task_struct * uses

Why, oh, why?

So that you can actually pass in a const struct task_struct * without having to cast it back to [non-const].

Why one would have a const struct task_struct * in the first place is a different matter.

But see http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=77adbfbf4cf96fedf9b75bb330704828c187b190

Quoted 2 lines

So that you can actually pass in a const struct task_struct * without having to cast it back to [non-const].

... which makes zero sense, because ...

Quoted 2 lines

Why one would have a const struct task_struct * in the first place is a different matter.

... exactly.

Quoted 1 line

But see http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;hwadbfbf4cf96fedf9b75bb330704828c187b190

That commit const-ified struct timespec * or struct timeval * arguments, which made sense because: (1) those functions really did not modify the passed structs, and, (2) callers that pass in const struct timeval * or const struct timespec * are indeed plausible (because one can plausibly have const timeval/timespec structs). As the changelog suggested, those callers

were having to cast away the const qualifier before passing to these functions to avoid seeing "passing argument discards qualifiers" warnings. While (1) holds true for the sched.h case here, (2) does not (and there are no warnings to shut up either).

If one really wants to go about "constifying" the kernel, then I think there's a lot of _data_ out there that should first be made const- qualified. xxx_ops function tables, and the like.

Quoted 19 lines · Satyam Sharma

Quoted 2 lines

So that you can actually pass in a const struct task_struct * without having to cast it back to [non-const].

... which makes zero sense, because ...

Quoted 2 lines

Why one would have a const struct task_struct * in the first place is a different matter.

... exactly.

Quoted 1 line

But see http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=77adbfbf4cf96fedf9b75bb330704828c187b190

That commit const-ified struct timespec * or struct timeval * arguments, which made sense because: (1) those functions really did not modify the passed structs, and, (2) callers that pass in const struct timeval * or const struct timespec * are indeed plausible (because one can plausibly have const timeval/timespec structs). As the changelog suggested, those callers

Quoted 4 lines

were having to cast away the const qualifier before passing to these functions to avoid seeing "passing argument discards qualifiers" warnings. While (1) holds true for the sched.h case here, (2) does not (and there are no warnings to shut up either).

"those callers". There was _exactly one_ caller, and that was an out-of-tree module. There were not any in-kernel callers before, and it did not generate any warning. That is perhaps why no one had constified it before me.

This does
not mean we should wait for a caller to pop up before constifying IMHO.

"those callers". There was _exactly one_ caller, and that was an out-of-tree module. There were not any in-kernel callers before, and it did not generate any warning. That is perhaps why no one had constified it before me. This does not mean we should wait for a caller to pop up before constifying IMHO.

Quoted 4 lines · Jan Engelhardt

"those callers". There was _exactly one_ caller, and that was an out-of-tree module. There were not any in-kernel callers before, and it did not generate any warning. That is perhaps why no one had constified it before me. This does not mean we should wait for a caller to pop up before constifying IMHO.

In this case we should just kill it instead of messing with constness.