Commit bcf9033e authored by Ard Biesheuvel's avatar Ard Biesheuvel
Browse files

sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y 



THREAD_INFO_IN_TASK moved the CPU field out of thread_info, but this
causes some issues on architectures that define raw_smp_processor_id()
in terms of this field, due to the fact that #include'ing linux/sched.h
to get at struct task_struct is problematic in terms of circular
dependencies.

Given that thread_info and task_struct are the same data structure
anyway when THREAD_INFO_IN_TASK=y, let's move it back so that having
access to the type definition of struct thread_info is sufficient to
reference the CPU number of the current task.

Note that this requires THREAD_INFO_IN_TASK's definition of the
task_thread_info() helper to be updated, as task_cpu() takes a
pointer-to-const, whereas task_thread_info() (which is used to generate
lvalues as well), needs a non-const pointer. So make it a macro instead.

Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 227d735d

arch/arm64/kernel/asm-offsets.c

+0 −1
Original line number Diff line number Diff line
@@ -27,7 +27,6 @@ 
int main(void)

{

  DEFINE(TSK_ACTIVE_MM,		offsetof(struct task_struct, active_mm));

  DEFINE(TSK_CPU,		offsetof(struct task_struct, cpu));

  BLANK();

  DEFINE(TSK_TI_CPU,		offsetof(struct task_struct, thread_info.cpu));

  DEFINE(TSK_TI_FLAGS,		offsetof(struct task_struct, thread_info.flags));

arch/arm64/kernel/head.S

+1 −1
Original line number Diff line number Diff line
@@ -412,7 +412,7 @@ SYM_FUNC_END(__create_page_tables) 
	scs_load \tsk



	adr_l	\tmp1, __per_cpu_offset

	ldr	w\tmp2, [\tsk, #TSK_CPU]

	ldr	w\tmp2, [\tsk, #TSK_TI_CPU]

	ldr	\tmp1, [\tmp1, \tmp2, lsl #3]

	set_this_cpu_offset \tmp1

	.endm

arch/powerpc/kernel/asm-offsets.c

+1 −1
Original line number Diff line number Diff line
@@ -93,7 +93,7 @@ int main(void) 
#endif /* CONFIG_PPC64 */

	OFFSET(TASK_STACK, task_struct, stack);

#ifdef CONFIG_SMP

	OFFSET(TASK_CPU, task_struct, cpu);

	OFFSET(TASK_CPU, task_struct, thread_info.cpu);

#endif



#ifdef CONFIG_LIVEPATCH

arch/powerpc/kernel/smp.c

+1 −1
Original line number Diff line number Diff line
@@ -1223,7 +1223,7 @@ static void cpu_idle_thread_init(unsigned int cpu, struct task_struct *idle) 
	paca_ptrs[cpu]->kstack = (unsigned long)task_stack_page(idle) +

				 THREAD_SIZE - STACK_FRAME_OVERHEAD;

#endif

	idle->cpu = cpu;

	task_thread_info(idle)->cpu = cpu;

	secondary_current = current_set[cpu] = idle;

}

include/linux/sched.h

+1 −12
Original line number Diff line number Diff line
@@ -750,10 +750,6 @@ struct task_struct { 
#ifdef CONFIG_SMP

	int				on_cpu;

	struct __call_single_node	wake_entry;

#ifdef CONFIG_THREAD_INFO_IN_TASK

	/* Current CPU: */

	unsigned int			cpu;

#endif

	unsigned int			wakee_flips;

	unsigned long			wakee_flip_decay_ts;

	struct task_struct		*last_wakee;
@@ -1886,10 +1882,7 @@ extern struct thread_info init_thread_info; 
extern unsigned long init_stack[THREAD_SIZE / sizeof(unsigned long)];



#ifdef CONFIG_THREAD_INFO_IN_TASK

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

{

	return &task->thread_info;

}

# define task_thread_info(task)	(&(task)->thread_info)

#elif !defined(__HAVE_THREAD_FUNCTIONS)

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

#endif
@@ -2114,11 +2107,7 @@ static __always_inline bool need_resched(void) 


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

{

#ifdef CONFIG_THREAD_INFO_IN_TASK

	return READ_ONCE(p->cpu);

#else

	return READ_ONCE(task_thread_info(p)->cpu);

#endif

}



extern void set_task_cpu(struct task_struct *p, unsigned int cpu);