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

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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: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ard Biesheuvel 2021-09-14 14:10:33 +02:00
parent 227d735d88
commit bcf9033e54
6 changed files with 4 additions and 20 deletions
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1
arch/arm64/kernel/asm-offsets.c
View File

@ -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));

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

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

@ -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

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;
}

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
@ -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);

4
kernel/sched/sched.h
View File

@ -1926,11 +1926,7 @@ 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
}