Messages in this thread Patch in this message |  | | From | Guo Ren <> | Date | Mon, 26 Sep 2022 07:25:30 +0800 | Subject | Re: [PATCH 2/4] riscv: consolidate ret_from_kernel_thread into ret_from_fork |
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On Mon, Sep 26, 2022 at 2:03 AM Jisheng Zhang <jszhang@kernel.org> wrote: > > The ret_from_kernel_thread() behaves similarly with ret_from_fork(), > the only difference is whether call the fn(arg) or not, this can be > acchieved by testing fn is NULL or not, I.E s0 is 0 or not. > > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > --- > arch/riscv/kernel/entry.S | 11 +++-------- > arch/riscv/kernel/process.c | 5 ++--- > 2 files changed, 5 insertions(+), 11 deletions(-) > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > index 2207cf44a3bc..a3e1ed2fa2ac 100644 > --- a/arch/riscv/kernel/entry.S > +++ b/arch/riscv/kernel/entry.S > @@ -323,20 +323,15 @@ END(handle_kernel_stack_overflow) > > ENTRY(ret_from_fork) > call schedule_tail > - move a0, sp /* pt_regs */ > - la ra, ret_from_exception > - tail syscall_exit_to_user_mode > -ENDPROC(ret_from_fork) > - > -ENTRY(ret_from_kernel_thread) > - call schedule_tail > + beqz s0, 1f /* not from kernel thread */ We can't use s0 as condition for ret_from_fork/ret_from_kernel_thread. The s0=0 is also okay for ret_from_fork.
/* p->thread holds context to be restored by __switch_to() */ if (unlikely(args->fn)) { /* Kernel thread */ memset(childregs, 0, sizeof(struct pt_regs)); childregs->gp = gp_in_global; /* Supervisor/Machine, irqs on: */ childregs->status = SR_PP | SR_PIE;
p->thread.ra = (unsigned long)ret_from_kernel_thread; p->thread.s[0] = (unsigned long)args->fn; p->thread.s[1] = (unsigned long)args->fn_arg; } else { *childregs = *(current_pt_regs()); ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ if (usp) /* User fork */ childregs->sp = usp; if (clone_flags & CLONE_SETTLS) childregs->tp = tls; childregs->a0 = 0; /* Return value of fork() */ p->thread.ra = (unsigned long)ret_from_fork; } p->thread.sp = (unsigned long)childregs; /* kernel sp */
> /* Call fn(arg) */ > move a0, s1 > jalr s0 > +1: > move a0, sp /* pt_regs */ > la ra, ret_from_exception > tail syscall_exit_to_user_mode > -ENDPROC(ret_from_kernel_thread) > +ENDPROC(ret_from_fork) > > #ifdef CONFIG_IRQ_STACKS > ENTRY(call_on_stack) > diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c > index ceb9ebab6558..67e7cd123ceb 100644 > --- a/arch/riscv/kernel/process.c > +++ b/arch/riscv/kernel/process.c > @@ -34,7 +34,6 @@ EXPORT_SYMBOL(__stack_chk_guard); > #endif > > extern asmlinkage void ret_from_fork(void); > -extern asmlinkage void ret_from_kernel_thread(void); > > void arch_cpu_idle(void) > { > @@ -172,7 +171,6 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) > /* Supervisor/Machine, irqs on: */ > childregs->status = SR_PP | SR_PIE; > > - p->thread.ra = (unsigned long)ret_from_kernel_thread; > p->thread.s[0] = (unsigned long)args->fn; > p->thread.s[1] = (unsigned long)args->fn_arg; > } else { > @@ -182,8 +180,9 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) > if (clone_flags & CLONE_SETTLS) > childregs->tp = tls; > childregs->a0 = 0; /* Return value of fork() */ > - p->thread.ra = (unsigned long)ret_from_fork; > + p->thread.s[0] = 0; > } > + p->thread.ra = (unsigned long)ret_from_fork; > p->thread.sp = (unsigned long)childregs; /* kernel sp */ > return 0; > } > -- > 2.34.1 >
-- Best Regards Guo Ren
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