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cpu-to-thread_info update for v5.16-rc1

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Cross-architecture update to move task_struct::cpu back into thread_info
 on arm64, x86, s390, powerpc, and riscv. All Acked by arch maintainers.
 
 Quoting Ard Biesheuvel:
 
 "Move task_struct::cpu back into thread_info
 
  Keeping CPU in task_struct is problematic for architectures that define
  raw_smp_processor_id() in terms of this field, as it requires
  linux/sched.h to be included, which causes a lot of pain in terms of
  circular dependencies (aka 'header soup')
 
  This series moves it back into thread_info (where it came from) for all
  architectures that enable THREAD_INFO_IN_TASK, addressing the header
  soup issue as well as some pointless differences in the implementations
  of task_cpu() and set_task_cpu()."
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Merge tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull thread_info update to move 'cpu' back from task_struct from Kees Cook:
 "Cross-architecture update to move task_struct::cpu back into
  thread_info on arm64, x86, s390, powerpc, and riscv. All Acked by arch
  maintainers.

  Quoting Ard Biesheuvel:

     'Move task_struct::cpu back into thread_info

      Keeping CPU in task_struct is problematic for architectures that
      define raw_smp_processor_id() in terms of this field, as it
      requires linux/sched.h to be included, which causes a lot of pain
      in terms of circular dependencies (aka 'header soup')

      This series moves it back into thread_info (where it came from)
      for all architectures that enable THREAD_INFO_IN_TASK, addressing
      the header soup issue as well as some pointless differences in the
      implementations of task_cpu() and set_task_cpu()'"

* tag 'cpu-to-thread_info-v5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  riscv: rely on core code to keep thread_info::cpu updated
  powerpc: smp: remove hack to obtain offset of task_struct::cpu
  sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y
  powerpc: add CPU field to struct thread_info
  s390: add CPU field to struct thread_info
  x86: add CPU field to struct thread_info
  arm64: add CPU field to struct thread_info
This commit is contained in:
Linus Torvalds 2021-11-01 17:00:05 -07:00
commit 01463374c5
15 changed files with 14 additions and 56 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/include/asm/thread_info.h
View File

@ -42,6 +42,7 @@ struct thread_info {
void *scs_base;
void *scs_sp;
#endif
u32 cpu;
};
#define thread_saved_pc(tsk) \

2
arch/arm64/kernel/asm-offsets.c
View File

@ -28,8 +28,8 @@
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));
DEFINE(TSK_TI_PREEMPT, offsetof(struct task_struct, thread_info.preempt_count));
#ifdef CONFIG_ARM64_SW_TTBR0_PAN

2
arch/arm64/kernel/head.S
View File

@ -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

11
arch/powerpc/Makefile
View File

@ -446,17 +446,6 @@ else
endif
endif
ifdef CONFIG_SMP
ifdef CONFIG_PPC32
prepare: task_cpu_prepare
PHONY += task_cpu_prepare
task_cpu_prepare: prepare0
$(eval KBUILD_CFLAGS += -D_TASK_CPU=$(shell awk '{if ($$2 == "TASK_CPU") print $$3;}' include/generated/asm-offsets.h))
endif # CONFIG_PPC32
endif # CONFIG_SMP
PHONY += checkbin
# Check toolchain versions:
# - gcc-4.6 is the minimum kernel-wide version so nothing required.

17
arch/powerpc/include/asm/smp.h
View File

@ -87,22 +87,7 @@ int is_cpu_dead(unsigned int cpu);
/* 32-bit */
extern int smp_hw_index[];
/*
* This is particularly ugly: it appears we can't actually get the definition
* of task_struct here, but we need access to the CPU this task is running on.
* Instead of using task_struct we're using _TASK_CPU which is extracted from
* asm-offsets.h by kbuild to get the current processor ID.
*
* This also needs to be safeguarded when building asm-offsets.s because at
* that time _TASK_CPU is not defined yet. It could have been guarded by
* _TASK_CPU itself, but we want the build to fail if _TASK_CPU is missing
* when building something else than asm-offsets.s
*/
#ifdef GENERATING_ASM_OFFSETS
#define raw_smp_processor_id() (0)
#else
#define raw_smp_processor_id() (*(unsigned int *)((void *)current + _TASK_CPU))
#endif
#define raw_smp_processor_id() (current_thread_info()->cpu)
#define hard_smp_processor_id() (smp_hw_index[smp_processor_id()])
static inline int get_hard_smp_processor_id(int cpu)

3
arch/powerpc/include/asm/thread_info.h
View File

@ -47,6 +47,9 @@
struct thread_info {
int preempt_count; /* 0 => preemptable,
<0 => BUG */
#ifdef CONFIG_SMP
unsigned int cpu;
#endif
unsigned long local_flags; /* private flags for thread */
#ifdef CONFIG_LIVEPATCH
unsigned long *livepatch_sp;

4
arch/powerpc/kernel/asm-offsets.c
View File

@ -9,8 +9,6 @@
* #defines from the assembly-language output.
*/
#define GENERATING_ASM_OFFSETS /* asm/smp.h */
#include <linux/compat.h>
#include <linux/signal.h>
#include <linux/sched.h>
@ -93,7 +91,7 @@ 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

2
arch/powerpc/kernel/smp.c
View File

@ -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;
}

1
arch/riscv/kernel/asm-offsets.c
View File

@ -33,7 +33,6 @@ void asm_offsets(void)
OFFSET(TASK_TI_PREEMPT_COUNT, task_struct, thread_info.preempt_count);
OFFSET(TASK_TI_KERNEL_SP, task_struct, thread_info.kernel_sp);
OFFSET(TASK_TI_USER_SP, task_struct, thread_info.user_sp);
OFFSET(TASK_TI_CPU, task_struct, thread_info.cpu);
OFFSET(TASK_THREAD_F0, task_struct, thread.fstate.f[0]);
OFFSET(TASK_THREAD_F1, task_struct, thread.fstate.f[1]);

5
arch/riscv/kernel/entry.S
View File

@ -543,11 +543,6 @@ ENTRY(__switch_to)
REG_L s9, TASK_THREAD_S9_RA(a4)
REG_L s10, TASK_THREAD_S10_RA(a4)
REG_L s11, TASK_THREAD_S11_RA(a4)
/* Swap the CPU entry around. */
lw a3, TASK_TI_CPU(a0)
lw a4, TASK_TI_CPU(a1)
sw a3, TASK_TI_CPU(a1)
sw a4, TASK_TI_CPU(a0)
/* The offset of thread_info in task_struct is zero. */
move tp, a1
ret

1
arch/riscv/kernel/head.S
View File

@ -318,7 +318,6 @@ clear_bss_done:
call setup_trap_vector
/* Restore C environment */
la tp, init_task
sw zero, TASK_TI_CPU(tp)
la sp, init_thread_union + THREAD_SIZE
#ifdef CONFIG_KASAN

1
arch/s390/include/asm/thread_info.h
View File

@ -37,6 +37,7 @@
struct thread_info {
unsigned long flags; /* low level flags */
unsigned long syscall_work; /* SYSCALL_WORK_ flags */
unsigned int cpu; /* current CPU */
};
/*

3
arch/x86/include/asm/thread_info.h
View File

@ -57,6 +57,9 @@ struct thread_info {
unsigned long flags; /* low level flags */
unsigned long syscall_work; /* SYSCALL_WORK_ flags */
u32 status; /* thread synchronous flags */
#ifdef CONFIG_SMP
u32 cpu; /* current CPU */
#endif
};
#define INIT_THREAD_INFO(tsk) \

13
include/linux/sched.h
View File

@ -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
@ -2133,11 +2126,7 @@ 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);

4
kernel/sched/sched.h
View File

@ -1912,11 +1912,7 @@ 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
WRITE_ONCE(p->cpu, cpu);
#else
WRITE_ONCE(task_thread_info(p)->cpu, cpu);
#endif
p->wake_cpu = cpu;
#endif
}