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Commit c65eacbe authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

sched/core: Allow putting thread_info into task_struct 



If an arch opts in by setting CONFIG_THREAD_INFO_IN_TASK_STRUCT,
then thread_info is defined as a single 'u32 flags' and is the first
entry of task_struct.  thread_info::task is removed (it serves no
purpose if thread_info is embedded in task_struct), and
thread_info::cpu gets its own slot in task_struct.

This is heavily based on a patch written by Linus.

Originally-from: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jann Horn <jann@thejh.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a0898196f0476195ca02713691a5037a14f2aac5.1473801993.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d896fa20

include/linux/init_task.h

+9 −0
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ 
#include <net/net_namespace.h>

#include <linux/sched/rt.h>



#include <asm/thread_info.h>



#ifdef CONFIG_SMP

# define INIT_PUSHABLE_TASKS(tsk)					\

	.pushable_tasks = PLIST_NODE_INIT(tsk.pushable_tasks, MAX_PRIO),
@@ -183,12 +185,19 @@ extern struct task_group root_task_group; 
# define INIT_KASAN(tsk)

#endif



#ifdef CONFIG_THREAD_INFO_IN_TASK

# define INIT_TASK_TI(tsk) .thread_info = INIT_THREAD_INFO(tsk),

#else

# define INIT_TASK_TI(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)	\

{									\

	INIT_TASK_TI(tsk)						\

	.state		= 0,						\

	.stack		= init_stack,					\

	.usage		= ATOMIC_INIT(2),				\

include/linux/sched.h

+34 −2
Original line number Diff line number Diff line
@@ -1458,6 +1458,13 @@ struct tlbflush_unmap_batch { 
};



struct task_struct {

#ifdef CONFIG_THREAD_INFO_IN_TASK

	/*

	 * For reasons of header soup (see current_thread_info()), this

	 * must be the first element of task_struct.

	 */

	struct thread_info thread_info;

#endif

	volatile long state;	/* -1 unrunnable, 0 runnable, >0 stopped */

	void *stack;

	atomic_t usage;
@@ -1467,6 +1474,9 @@ struct task_struct { 
#ifdef CONFIG_SMP

	struct llist_node wake_entry;

	int on_cpu;

#ifdef CONFIG_THREAD_INFO_IN_TASK

	unsigned int cpu;	/* current CPU */

#endif

	unsigned int wakee_flips;

	unsigned long wakee_flip_decay_ts;

	struct task_struct *last_wakee;
@@ -2588,7 +2598,9 @@ extern void set_curr_task(int cpu, struct task_struct *p); 
void yield(void);



union thread_union {

#ifndef CONFIG_THREAD_INFO_IN_TASK

	struct thread_info thread_info;

#endif

	unsigned long stack[THREAD_SIZE/sizeof(long)];

};
@@ -3076,10 +3088,26 @@ static inline void threadgroup_change_end(struct task_struct *tsk) 
	cgroup_threadgroup_change_end(tsk);

}



#ifndef __HAVE_THREAD_FUNCTIONS

#ifdef CONFIG_THREAD_INFO_IN_TASK



static inline struct thread_info *task_thread_info(struct task_struct *task)

{

	return &task->thread_info;

}

static inline void *task_stack_page(const struct task_struct *task)

{

	return task->stack;

}

#define setup_thread_stack(new,old)	do { } while(0)

static inline unsigned long *end_of_stack(const struct task_struct *task)

{

	return task->stack;

}



#elif !defined(__HAVE_THREAD_FUNCTIONS)



#define task_thread_info(task)	((struct thread_info *)(task)->stack)

#define task_stack_page(task)	((task)->stack)

#define task_stack_page(task)	((void *)(task)->stack)



static inline void setup_thread_stack(struct task_struct *p, struct task_struct *org)

{
@@ -3379,7 +3407,11 @@ static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume) 


static inline unsigned int task_cpu(const struct task_struct *p)

{

#ifdef CONFIG_THREAD_INFO_IN_TASK

	return p->cpu;

#else

	return task_thread_info(p)->cpu;

#endif

}



static inline int task_node(const struct task_struct *p)

include/linux/thread_info.h

+15 −0
Original line number Diff line number Diff line
@@ -13,6 +13,21 @@ 
struct timespec;

struct compat_timespec;



#ifdef CONFIG_THREAD_INFO_IN_TASK

struct thread_info {

	u32			flags;		/* low level flags */

};



#define INIT_THREAD_INFO(tsk)			\

{						\

	.flags		= 0,			\

}

#endif



#ifdef CONFIG_THREAD_INFO_IN_TASK

#define current_thread_info() ((struct thread_info *)current)

#endif



/*

 * System call restart block.

 */

init/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -26,6 +26,13 @@ config IRQ_WORK 
config BUILDTIME_EXTABLE_SORT

	bool



config THREAD_INFO_IN_TASK

	bool

	help

	  Select this to move thread_info off the stack into task_struct.  To

	  make this work, an arch will need to remove all thread_info fields

	  except flags and fix any runtime bugs.



menu "General setup"



config BROKEN

init/init_task.c

+5 −2
Original line number Diff line number Diff line
@@ -22,5 +22,8 @@ EXPORT_SYMBOL(init_task); 
 * Initial thread structure. Alignment of this is handled by a special

 * linker map entry.

 */

union thread_union init_thread_union __init_task_data =

	{ INIT_THREAD_INFO(init_task) };
 
union thread_union init_thread_union __init_task_data = {

#ifndef CONFIG_THREAD_INFO_IN_TASK

	INIT_THREAD_INFO(init_task)

#endif

};