riscv: implement arch_switch()
The move to arch_switch() is a prerequisite for SMP support. Make it optimal without the need for an ECALL roundtrip on every context switch. Performance numbers from tests/benchmarks/sched: Before: unpend 107 ready 102 switch 188 pend 218 tot 615 (avg 615) After: unpend 107 ready 102 switch 170 pend 217 tot 596 (avg 595) Signed-off-by: Nicolas Pitre <npitre@baylibre.com>
This commit is contained in:
Nicolas Pitre
Anas Nashif
parent
247d2c8e3b
commit
ce8dabfe9e
12 changed files with 197 additions and 234 deletions
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@ -41,35 +41,6 @@
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op fa6, __z_arch_esf_t_fa6_OFFSET(reg) ;\
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op fa7, __z_arch_esf_t_fa7_OFFSET(reg) ;
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#define DO_FP_CALLEE_SAVED(op, reg) \
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op fs0, _thread_offset_to_fs0(reg) ;\
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op fs1, _thread_offset_to_fs1(reg) ;\
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op fs2, _thread_offset_to_fs2(reg) ;\
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op fs3, _thread_offset_to_fs3(reg) ;\
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op fs4, _thread_offset_to_fs4(reg) ;\
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op fs5, _thread_offset_to_fs5(reg) ;\
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op fs6, _thread_offset_to_fs6(reg) ;\
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op fs7, _thread_offset_to_fs7(reg) ;\
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op fs8, _thread_offset_to_fs8(reg) ;\
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op fs9, _thread_offset_to_fs9(reg) ;\
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op fs10, _thread_offset_to_fs10(reg) ;\
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op fs11, _thread_offset_to_fs11(reg) ;
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#define DO_CALLEE_SAVED(op, reg) \
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op s0, _thread_offset_to_tp(reg) ;\
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op s0, _thread_offset_to_s0(reg) ;\
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op s1, _thread_offset_to_s1(reg) ;\
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op s2, _thread_offset_to_s2(reg) ;\
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op s3, _thread_offset_to_s3(reg) ;\
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op s4, _thread_offset_to_s4(reg) ;\
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op s5, _thread_offset_to_s5(reg) ;\
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op s6, _thread_offset_to_s6(reg) ;\
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op s7, _thread_offset_to_s7(reg) ;\
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op s8, _thread_offset_to_s8(reg) ;\
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op s9, _thread_offset_to_s9(reg) ;\
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op s10, _thread_offset_to_s10(reg) ;\
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op s11, _thread_offset_to_s11(reg) ;
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#define DO_CALLER_SAVED(op) \
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op ra, __z_arch_esf_t_ra_OFFSET(sp) ;\
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op t0, __z_arch_esf_t_t0_OFFSET(sp) ;\
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@ -101,25 +72,16 @@ GTEXT(__soc_restore_context)
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#endif /* CONFIG_RISCV_SOC_CONTEXT_SAVE */
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GTEXT(z_riscv_fatal_error)
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GTEXT(_k_neg_eagain)
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GTEXT(_is_next_thread_current)
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GTEXT(z_get_next_ready_thread)
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GTEXT(z_get_next_switch_handle)
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GTEXT(z_riscv_switch)
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GTEXT(z_riscv_thread_start)
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#ifdef CONFIG_INSTRUMENT_THREAD_SWITCHING
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GTEXT(z_thread_mark_switched_in)
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GTEXT(z_thread_mark_switched_out)
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#ifdef CONFIG_TRACING
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GTEXT(sys_trace_isr_enter)
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#endif
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#endif
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#ifdef CONFIG_USERSPACE
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GDATA(_k_syscall_table)
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GTEXT(z_riscv_configure_user_allowed_stack)
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#endif
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#ifdef CONFIG_PMP_STACK_GUARD
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GTEXT(z_riscv_configure_stack_guard)
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#endif
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/* exports */
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@ -291,21 +253,15 @@ is_kernel_syscall:
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/* Determine what to do. Operation code is in a7. */
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lr a7, __z_arch_esf_t_a7_OFFSET(sp)
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ASSUME_EQUAL(RV_ECALL_CONTEXT_SWITCH, 0)
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beqz a7, reschedule
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ASSUME_EQUAL(RV_ECALL_RUNTIME_EXCEPT, 0)
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beqz a7, do_fault
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#if defined(CONFIG_IRQ_OFFLOAD)
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addi a7, a7, -1
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ASSUME_EQUAL(RV_ECALL_IRQ_OFFLOAD, 1)
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beqz a7, do_irq_offload
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addi a7, a7, -1
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#else
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addi a7, a7, -2
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#endif
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ASSUME_EQUAL(RV_ECALL_RUNTIME_EXCEPT, 2)
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beqz a7, do_fault
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/* default fault code is K_ERR_KERNEL_OOPS */
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li a0, 3
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j 1f
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@ -467,102 +423,32 @@ irq_done:
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#endif
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reschedule:
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/* Get reference to _kernel */
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la t1, _kernel
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/*
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* Check if next thread to schedule is current thread.
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* If yes do not perform a reschedule
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*/
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lr t2, _kernel_offset_to_current(t1)
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lr t3, _kernel_offset_to_ready_q_cache(t1)
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beq t3, t2, no_reschedule
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#if CONFIG_INSTRUMENT_THREAD_SWITCHING
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call z_thread_mark_switched_out
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#endif
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/* Get reference to _kernel */
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la t0, _kernel
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/* Get pointer to _kernel.current */
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lr t1, _kernel_offset_to_current(t0)
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/*
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* Save callee-saved registers of current kernel thread
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* prior to handle context-switching
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*/
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DO_CALLEE_SAVED(sr, t1)
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#if defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)
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/* Assess whether floating-point registers need to be saved. */
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lb t2, _thread_offset_to_user_options(t1)
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andi t2, t2, K_FP_REGS
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beqz t2, skip_store_fp_callee_saved
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frcsr t2
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sw t2, _thread_offset_to_fcsr(t1)
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DO_FP_CALLEE_SAVED(fsr, t1)
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skip_store_fp_callee_saved:
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#endif /* CONFIG_FPU && CONFIG_FPU_SHARING */
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/*
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* Save stack pointer of current thread and set the default return value
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* of z_swap to _k_neg_eagain for the thread.
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*/
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sr sp, _thread_offset_to_sp(t1)
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la t2, _k_neg_eagain
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lw t3, 0(t2)
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sw t3, _thread_offset_to_swap_return_value(t1)
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/* Get next thread to schedule. */
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lr t1, _kernel_offset_to_ready_q_cache(t0)
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/* Set _kernel.current to new thread loaded in t1 */
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sr t1, _kernel_offset_to_current(t0)
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/* Switch to new thread stack */
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lr sp, _thread_offset_to_sp(t1)
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/* Restore callee-saved registers of new thread */
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DO_CALLEE_SAVED(lr, t1)
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#if defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)
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/* Determine if we need to restore floating-point registers. */
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lb t2, _thread_offset_to_user_options(t1)
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andi t2, t2, K_FP_REGS
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beqz t2, skip_load_fp_callee_saved
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/*
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* If we are switching from a thread with floating-point disabled the
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* mstatus FS bits will still be cleared, which can cause an illegal
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* instruction fault. Set the FS state before restoring the registers.
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* mstatus will be restored later on.
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*/
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li t2, MSTATUS_FS_INIT
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csrs mstatus, t2
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lw t2, _thread_offset_to_fcsr(t1)
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fscsr t2
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DO_FP_CALLEE_SAVED(flr, t1)
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skip_load_fp_callee_saved:
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#endif /* CONFIG_FPU && CONFIG_FPU_SHARING */
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#ifdef CONFIG_PMP_STACK_GUARD
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mv a0, t1 /* kernel current */
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jal ra, z_riscv_configure_stack_guard
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#endif /* CONFIG_PMP_STACK_GUARD */
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#ifdef CONFIG_USERSPACE
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la t0, _kernel
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lr a0, _kernel_offset_to_current(t0)
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jal ra, z_riscv_configure_user_allowed_stack
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#endif /* CONFIG_USERSPACE */
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lr a1, _kernel_offset_to_current(t0)
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#if CONFIG_INSTRUMENT_THREAD_SWITCHING
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call z_thread_mark_switched_in
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#endif
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/*
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* Get next thread to schedule with z_get_next_switch_handle().
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* We pass it a NULL as we didn't save the whole thread context yet.
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* If no scheduling is necessary then NULL will be returned.
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*/
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addi sp, sp, -16
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sr a1, 0(sp)
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mv a0, zero
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call z_get_next_switch_handle
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lr a1, 0(sp)
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addi sp, sp, 16
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beqz a0, no_reschedule
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/*
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* Perform context switch:
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* a0 = new thread
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* a1 = old thread
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*/
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call z_riscv_switch
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z_riscv_thread_start:
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no_reschedule:
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#ifdef CONFIG_RISCV_SOC_CONTEXT_SAVE
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