feat(sched): 协作 + 时间片抢占（IRQ0 返回用户态时切换）
原先 timer_tick 只置 needs_reschedule，唯一消费点是 SPAWN 阻塞循环，纯计算线程永不被切走。① 抢占点：isr32_handler 在 timer_handler（含 pic.eoi(0)/apic.eoi）返回之后、且 from_user != 0（ISR 入口读 CS 低两位）时调用 try_reschedule；栈切换仍在 _do_switch。只对 Ring3 返回路径生效，内核临界区/syscall 中途不切。② 中断帧保留在被切线程内核栈上，靠 rsp 切换自然保存/恢复，不拷贝、不在切换中途 iretq。③ 修正全局 _isr_scratch 跨线程覆盖：ISR_SAVE_CLOBBERED 把 rax/rcx/r8-r11 存在全局 scratch，抢占后跨线程会互相覆盖；_do_switch 现按 tid 保存/恢复（_isr_scratch_tbl[16*6]）。④ ISR 走中断门 IF=0，_if_saved=0，切回后不 sti，由 iretq 用用户 RFLAGS 恢复；_yield_lock 防嵌套。⑤ 单核前提（_sched_ptr/tick_count 非 per-CPU）。⑥ yield_now 语义、SCHED_QUANTUM=10、Gargantua 分块均未改。已知缺口：中断帧未保存 XMM/MXCSR，FP 密集 app 在异步抢占下有 XMM 被覆盖风险，待补 fxsave/fxrstor。
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@@ -238,7 +238,11 @@ export def isr28_handler(): isrCommonhandler(28)
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export def isr29_handler(): isrCommonhandler(29)
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export def isr30_handler(): isrCommonhandler(30)
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export def isr31_handler(): isrCommonhandler(31)
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export def isr32_handler(): timer.timer_handler()
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export def isr32_handler(from_user: int):
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timer.timer_handler()
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# 定时 IRQ 已 EOI，处理完毕；仅在返回用户态时消费时间片，内核态不抢占。
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if from_user != 0:
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sched.Scheduler.try_reschedule()
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export def isr33_handler():
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handler: irq_handler_t = irqGetHandler(1)
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@@ -134,6 +134,8 @@ isr\num\()_frame_ready:
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push r13
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push r14
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push r15
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# is_user 作为第 1 个参数（rdi）传给处理函数，供其判断"返回用户态"时是否抢占
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mov rdi, rcx
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call isr\num\()_handler
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pop r15
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pop r14
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@@ -332,6 +334,8 @@ isr\num\()_frame_ready:
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push r13
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push r14
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push r15
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# is_user 作为第 1 个参数（rdi）传给处理函数，供其判断"返回用户态"时是否抢占
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mov rdi, rcx
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call isr\num\()_handler
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pop r15
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pop r14
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@@ -16,6 +16,10 @@ define SCHED_QUANTUM = 10
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_yield_cnt: uint32 = 0
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_yield_lock: int = 0
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# ISR scratch 是全局槽（isr.s）；抢占后一个 ISR 会跨越其它线程的 ISR，故切换时按线程保存/恢复。
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export _isr_scratch_tbl: [MAX_THREADS * 6]uint64
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export _switch_old_tid: int = 0
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export _switch_new_tid: int = 0
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class Thread:
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@@ -92,7 +96,8 @@ class Scheduler:
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@staticmethod
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def _yield():
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global _switch_old_rsp, _switch_new_rsp, _yield_cnt, _yield_lock
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global _switch_old_rsp, _switch_new_rsp, _yield_cnt, _yield_lock
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global _switch_old_tid, _switch_new_tid
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_if_saved: int = 0
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__asm__(f"""pushfq
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pop rax
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@@ -147,6 +152,8 @@ class Scheduler:
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if next_ks != 0:
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gdt.set_tss_rsp0(next_ks)
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cpu.set_kernel_rsp0(next_ks)
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_switch_old_tid = old_tid
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_switch_new_tid = next_tid
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_yield_lock = 0
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_do_switch()
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if _if_saved:
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@@ -304,10 +311,44 @@ def _do_switch():
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push r14
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push r15
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pushfq
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# 按线程保存 ISR scratch（被抢占的 ISR 会跨越其它线程的 ISR）
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mov eax, dword ptr [rip + _switch_old_tid]
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imul rax, rax, 48
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lea rdx, [rip + _isr_scratch_tbl]
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add rdx, rax
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mov rcx, qword ptr [rip + _isr_scratch]
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mov qword ptr [rdx], rcx
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mov rcx, qword ptr [rip + _isr_scratch + 8]
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mov qword ptr [rdx + 8], rcx
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mov rcx, qword ptr [rip + _isr_scratch + 16]
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mov qword ptr [rdx + 16], rcx
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mov rcx, qword ptr [rip + _isr_scratch + 24]
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mov qword ptr [rdx + 24], rcx
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mov rcx, qword ptr [rip + _isr_scratch + 32]
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mov qword ptr [rdx + 32], rcx
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mov rcx, qword ptr [rip + _isr_scratch + 40]
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mov qword ptr [rdx + 40], rcx
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mov rax, qword ptr [rip + _switch_old_rsp]
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mov qword ptr [rax], rsp
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mov rax, qword ptr [rip + _switch_new_rsp]
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mov rsp, qword ptr [rax]
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# 恢复切入线程的 scratch（不在 ISR 中时内容无意义，覆盖无害）
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mov eax, dword ptr [rip + _switch_new_tid]
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imul rax, rax, 48
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lea rdx, [rip + _isr_scratch_tbl]
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add rdx, rax
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mov rcx, qword ptr [rdx]
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mov qword ptr [rip + _isr_scratch], rcx
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mov rcx, qword ptr [rdx + 8]
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mov qword ptr [rip + _isr_scratch + 8], rcx
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mov rcx, qword ptr [rdx + 16]
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mov qword ptr [rip + _isr_scratch + 16], rcx
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mov rcx, qword ptr [rdx + 24]
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mov qword ptr [rip + _isr_scratch + 24], rcx
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mov rcx, qword ptr [rdx + 32]
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mov qword ptr [rip + _isr_scratch + 32], rcx
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mov rcx, qword ptr [rdx + 40]
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mov qword ptr [rip + _isr_scratch + 40], rcx
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popfq
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pop r15
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pop r14
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@@ -317,7 +358,7 @@ def _do_switch():
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pop rbx
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pop rax
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ret""",
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op=[ASM_DESCR.CLOBBER_MEMORY])
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op=[ASM_DESCR.CLOBBER_MEMORY, ASM_DESCR.CLOBBER_RCX, ASM_DESCR.CLOBBER_RDX])
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# Thread 布局：rsp0/stack8/stack_size16/func24/arg32/state40/tid44/pid48/kern_stack56
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# ⇒ sizeof(Thread) = 64，Scheduler.threads[16] 占 1024 字节 ⇒ current_tid 在 +1024。
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