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Subject[PATCH 4.4 1/7] sched/core: Allow putting thread_info into task_struct
Date
From: Andy Lutomirski <luto@kernel.org>

commit c65eacbe290b8141554c71b2c94489e73ade8c8d upstream.

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: Andy 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: Ingo Molnar <mingo@kernel.org>
Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
---
include/linux/init_task.h | 9 +++++++++
include/linux/sched.h | 36 ++++++++++++++++++++++++++++++++++--
include/linux/thread_info.h | 15 +++++++++++++++
init/Kconfig | 7 +++++++
init/init_task.c | 7 +++++--
kernel/sched/sched.h | 4 ++++
6 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 1c1ff7e4faa4..d25d3f70ee99 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -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_thread_info, \
.usage = ATOMIC_INIT(2), \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1218980f53de..d6b2e77aad3f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1389,6 +1389,13 @@ 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;
@@ -1398,6 +1405,9 @@ 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;
@@ -2440,7 +2450,9 @@ 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)];
};

@@ -2840,10 +2852,26 @@ 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)
{
@@ -3135,7 +3163,11 @@ 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)
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 646891f3bc1e..2813de75a96e 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -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.
*/
diff --git a/init/Kconfig b/init/Kconfig
index 47b0bdcf33c2..5dec7d424980 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -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
diff --git a/init/init_task.c b/init/init_task.c
index ba0a7f362d9e..11f83be1fa79 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -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
+};
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 8b96df04ba78..8afd9d62c56e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -978,7 +978,11 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
* per-task data have been completed by this moment.
*/
smp_wmb();
+#ifdef CONFIG_THREAD_INFO_IN_TASK
+ p->cpu = cpu;
+#else
task_thread_info(p)->cpu = cpu;
+#endif
p->wake_cpu = cpu;
#endif
}
--
2.17.2
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