Commit 18ed1c01 authored by Ard Biesheuvel's avatar Ard Biesheuvel
Browse files

ARM: smp: Enable THREAD_INFO_IN_TASK 



Now that we no longer rely on thread_info living at the base of the task
stack to be able to access the 'current' pointer, we can wire up the
generic support for moving thread_info into the task struct itself.

Note that this requires us to update the cpu field in thread_info
explicitly, now that the core code no longer does so. Ideally, we would
switch the percpu code to access the cpu field in task_struct instead,
but this unleashes #include circular dependency hell.

Co-developed-by: default avatarKeith Packard <keithpac@amazon.com>
Signed-off-by: default avatarKeith Packard <keithpac@amazon.com>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Tested-by: default avatarAmit Daniel Kachhap <amit.kachhap@arm.com>
parent 50596b75

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -125,6 +125,7 @@ config ARM 
	select PERF_USE_VMALLOC

	select RTC_LIB

	select SYS_SUPPORTS_APM_EMULATION

	select THREAD_INFO_IN_TASK if CURRENT_POINTER_IN_TPIDRURO

	select TRACE_IRQFLAGS_SUPPORT if !CPU_V7M

	# Above selects are sorted alphabetically; please add new ones

	# according to that.  Thanks.

arch/arm/include/asm/assembler.h

+5 −0
Original line number Diff line number Diff line
@@ -227,10 +227,15 @@ 
 * Get current thread_info.

 */

	.macro	get_thread_info, rd

#ifdef CONFIG_THREAD_INFO_IN_TASK

	/* thread_info is the first member of struct task_struct */

	get_current \rd

#else

 ARM(	mov	\rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT	)

 THUMB(	mov	\rd, sp			)

 THUMB(	lsr	\rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT	)

	mov	\rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT

#endif

	.endm



/*

arch/arm/include/asm/switch_to.h

+14 −0
Original line number Diff line number Diff line
@@ -23,9 +23,23 @@ 
 */

extern struct task_struct *__switch_to(struct task_struct *, struct thread_info *, struct thread_info *);



static inline void set_ti_cpu(struct task_struct *p)

{

#ifdef CONFIG_THREAD_INFO_IN_TASK

	/*

	 * The core code no longer maintains the thread_info::cpu field once

	 * CONFIG_THREAD_INFO_IN_TASK is in effect, but we rely on it for

	 * raw_smp_processor_id(), which cannot access struct task_struct*

	 * directly for reasons of circular #inclusion hell.

	 */

	task_thread_info(p)->cpu = task_cpu(p);

#endif

}



#define switch_to(prev,next,last)					\

do {									\

	__complete_pending_tlbi();					\

	set_ti_cpu(next);						\

	if (IS_ENABLED(CONFIG_CURRENT_POINTER_IN_TPIDRURO))		\

		__this_cpu_write(__entry_task, next);			\

	last = __switch_to(prev,task_thread_info(prev), task_thread_info(next));	\

arch/arm/include/asm/thread_info.h

+9 −1
Original line number Diff line number Diff line
@@ -54,7 +54,9 @@ struct cpu_context_save { 
struct thread_info {

	unsigned long		flags;		/* low level flags */

	int			preempt_count;	/* 0 => preemptable, <0 => bug */

#ifndef CONFIG_THREAD_INFO_IN_TASK

	struct task_struct	*task;		/* main task structure */

#endif

	__u32			cpu;		/* cpu */

	__u32			cpu_domain;	/* cpu domain */

	struct cpu_context_save	cpu_context;	/* cpu context */
@@ -70,11 +72,16 @@ struct thread_info { 


#define INIT_THREAD_INFO(tsk)						\

{									\

	.task		= &tsk,						\

	INIT_THREAD_INFO_TASK(tsk)					\

	.flags		= 0,						\

	.preempt_count	= INIT_PREEMPT_COUNT,				\

}



#ifdef CONFIG_THREAD_INFO_IN_TASK

#define INIT_THREAD_INFO_TASK(tsk)

#else

#define INIT_THREAD_INFO_TASK(tsk)	.task = &(tsk),



/*

 * how to get the thread information struct from C

 */
@@ -85,6 +92,7 @@ static inline struct thread_info *current_thread_info(void) 
	return (struct thread_info *)

		(current_stack_pointer & ~(THREAD_SIZE - 1));

}

#endif



#define thread_saved_pc(tsk)	\

	((unsigned long)(task_thread_info(tsk)->cpu_context.pc))

arch/arm/kernel/asm-offsets.c

+2 −0
Original line number Diff line number Diff line
@@ -43,7 +43,9 @@ int main(void) 
  BLANK();

  DEFINE(TI_FLAGS,		offsetof(struct thread_info, flags));

  DEFINE(TI_PREEMPT,		offsetof(struct thread_info, preempt_count));

#ifndef CONFIG_THREAD_INFO_IN_TASK

  DEFINE(TI_TASK,		offsetof(struct thread_info, task));

#endif

  DEFINE(TI_CPU,		offsetof(struct thread_info, cpu));

  DEFINE(TI_CPU_DOMAIN,		offsetof(struct thread_info, cpu_domain));

  DEFINE(TI_CPU_SAVE,		offsetof(struct thread_info, cpu_context));