Messages in this thread | | | From | Ard Biesheuvel <> | Date | Thu, 30 Sep 2021 15:12:24 +0200 | Subject | Re: [PATCH v2 5/7] sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y |
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On Thu, 30 Sept 2021 at 15:09, Christophe Leroy <christophe.leroy@csgroup.eu> wrote: > > > > Le 30/09/2021 à 14:58, Ard Biesheuvel a écrit : > > 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> > > --- > > arch/arm64/kernel/asm-offsets.c | 1 - > > arch/arm64/kernel/head.S | 2 +- > > arch/powerpc/kernel/asm-offsets.c | 2 +- > > arch/powerpc/kernel/smp.c | 2 +- > > include/linux/sched.h | 13 +------------ > > kernel/sched/sched.h | 4 ---- > > 6 files changed, 4 insertions(+), 20 deletions(-) > > > > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > > index cee9f3e9f906..0bfc048221af 100644 > > --- a/arch/arm64/kernel/asm-offsets.c > > +++ b/arch/arm64/kernel/asm-offsets.c > > @@ -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)); > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > index 17962452e31d..6a98f1a38c29 100644 > > --- a/arch/arm64/kernel/head.S > > +++ b/arch/arm64/kernel/head.S > > @@ -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] > > Why do you need to change the name ? > > For powerpc64, you leave TASK_CPU. >
Because arm64 has a clear idiom here, where TSK_TI_ is used for thread_info fields accessed via a task_struct pointer. Also, it only occurs once in the code.
Power does not seem to have this idiom, and TASK_CPU is used in many more places, so I don't think it makes sense to change its name.
> > ldr \tmp1, [\tmp1, \tmp2, lsl #3] > > set_this_cpu_offset \tmp1 > > .endm > > diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c > > index e563d3222d69..e37e4546034e 100644 > > --- a/arch/powerpc/kernel/asm-offsets.c > > +++ b/arch/powerpc/kernel/asm-offsets.c > > @@ -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 > > ...
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