On 11/4/21 09:26, Ard Biesheuvel wrote:
> In commit 2214c0e77259 ("parisc: Move thread_info into task struct")
> PA-RISC gained support for THREAD_INFO_IN_TASK while changes were
> already underway to keep the CPU field in thread_info rather than move
> it into task_struct when THREAD_INFO_IN_TASK is enabled. The result is a
> broken build for all PA-RISC configs that enable SMP.
>
> So let's partially revert that commit, and get rid of the ugly hack to
> get at the offset of task_struct::cpu without having to include
> linux/sched.h, and put the CPU field back where it was before.
>
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Fixes: bcf9033e5449 ("sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y")
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Thanks Ard!
I actually had the same patch finished right now too :-)
One small nid though. See below...
> ---
> arch/parisc/include/asm/smp.h | 19 ++-----------------
> arch/parisc/include/asm/thread_info.h | 2 ++
> arch/parisc/kernel/asm-offsets.c | 4 +---
> arch/parisc/kernel/smp.c | 2 +-
> 4 files changed, 6 insertions(+), 21 deletions(-)
>
> diff --git a/arch/parisc/include/asm/smp.h b/arch/parisc/include/asm/smp.h
> index 16d41127500e..cba55abf7bac 100644
> --- a/arch/parisc/include/asm/smp.h
> +++ b/arch/parisc/include/asm/smp.h
> @@ -34,23 +34,8 @@ extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
>
> #endif /* !ASSEMBLY */
>
> -/*
> - * 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
> -#include <asm/asm-offsets.h>
> -#define raw_smp_processor_id() (*(unsigned int *)((void *)current + TASK_CPU))
> -#endif
> +#define raw_smp_processor_id() (current_thread_info()->cpu)
> +
> #else /* CONFIG_SMP */
>
> static inline void smp_send_all_nop(void) { return; }
> diff --git a/arch/parisc/include/asm/thread_info.h b/arch/parisc/include/asm/thread_info.h
> index 75657c2c54e1..d6268834bfa5 100644
> --- a/arch/parisc/include/asm/thread_info.h
> +++ b/arch/parisc/include/asm/thread_info.h
> @@ -8,12 +8,14 @@
>
> struct thread_info {
> unsigned long flags; /* thread_info flags (see TIF_*) */
> + __u32 cpu; /* current CPU */
> int preempt_count; /* 0=premptable, <0=BUG; will also serve as bh-counter */
> };
>
> #define INIT_THREAD_INFO(tsk) \
> { \
> .flags = 0, \
> + .cpu = 0, \
> .preempt_count = INIT_PREEMPT_COUNT, \
> }
>
> diff --git a/arch/parisc/kernel/asm-offsets.c b/arch/parisc/kernel/asm-offsets.c
> index e35154035441..629d38e36e22 100644
> --- a/arch/parisc/kernel/asm-offsets.c
> +++ b/arch/parisc/kernel/asm-offsets.c
> @@ -14,8 +14,6 @@
> * Copyright (C) 2003 James Bottomley <jejb at parisc-linux.org>
> */
>
> -#define GENERATING_ASM_OFFSETS /* asm/smp.h */
> -
> #include <linux/types.h>
> #include <linux/sched.h>
> #include <linux/thread_info.h>
> @@ -40,7 +38,7 @@ int main(void)
> DEFINE(TASK_TI_FLAGS, offsetof(struct task_struct, thread_info.flags));
> DEFINE(TASK_STACK, offsetof(struct task_struct, stack));
> #ifdef CONFIG_SMP
> - DEFINE(TASK_CPU, offsetof(struct task_struct, cpu));
> + DEFINE(TASK_CPU, offsetof(struct task_struct, thread_info.cpu));
> #endif
The TASK_CPU define isn't needed any longer.
So, the whole part inside #ifdef..#endif can go.
If it's Ok for you I'll clean up your patch and submit
all with the next pull request to Linus later today.
Helge
> BLANK();
> DEFINE(TASK_REGS, offsetof(struct task_struct, thread.regs));
> diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
> index 171925285f3e..0cd97fa004c5 100644
> --- a/arch/parisc/kernel/smp.c
> +++ b/arch/parisc/kernel/smp.c
> @@ -339,7 +339,7 @@ int smp_boot_one_cpu(int cpuid, struct task_struct *idle)
> const struct cpuinfo_parisc *p = &per_cpu(cpu_data, cpuid);
> long timeout;
>
> - idle->cpu = cpuid;
> + task_thread_info(idle)->cpu = cpuid;
>
> /* Let _start know what logical CPU we're booting
> ** (offset into init_tasks[],cpu_data[])
>
