Hi,
In the previous patch to irqtab.c I inadvertently introduced a
bug. Also I found more bugs
to the original code. These are:
4. The call to the bios timer processing must be done before the
call to schedule, because
it may happen that schedule does not return to this function
(immediately).
5. The call to do_IRQ should be done with interrupts enabled.
6. Does not check that int_stack is in use.
The following patch corrects the bugs mentioned in the previous
message and bug #4 of
this message. Please ignore the previous patch.
Greetings,
Juan
--- arch/i86/kernel/irqtab.c 2002-10-31 19:04:25.000000000 -0600
+++ ../irqtab.c 2012-02-01 18:31:39.000000000 -0600
@@ -36,6 +36,11 @@
#define bios_call_cnt cseg_bios_call_cnt
#endif
+#ifdef CONFIG_ROMCODE
+ #define SEG_IRQ_DATA es
+#else
+ #define SEG_IRQ_DATA cs
+#endif
#ifndef S_SPLINT_S
#asm
@@ -105,27 +110,26 @@
mov dx,ds ;the original value
cli ;just here
- xor ax,ax
- mov es,ax ;intr table
-
#ifdef CONFIG_ROMCODE
mov ax,#CONFIG_ROM_IRQ_DATA
-#else
- mov ax,cs
+ mov es,ax
#endif
- mov ds,ax
- mov stashed_ds,dx
+ seg SEG_IRQ_DATA
+ mov stashed_ds,ds
+
+ xor ax,ax
+ mov es,ax ;intr table
seg es ;insert new timer intr
mov bx,[32]
- mov off_stashed_irq0, bx ; the old one
+ mov off_stashed_irq0_l, bx ; the old one
lea ax,_irq0
seg es
mov [32],ax
seg es
mov bx,[34]
- mov seg_stashed_irq0, bx
+ mov seg_stashed_irq0_l, bx
mov ax,cs
seg es
mov [34],ax
@@ -430,7 +434,7 @@
! Save all registers
!
- cli ! Might not be disabled on an exception
+! cli ! Might not be disabled on an exception
push ds
push es
push bx
@@ -445,23 +449,18 @@
!
#ifdef CONFIG_ROMCODE
mov bx,#CONFIG_ROM_IRQ_DATA
-#else
- mov bx,cs
+ mov es,bx
#endif
- mov ds,bx
-
- mov stashed_irq,ax ! Save IRQ number
- mov ax,ss ! Get current SS
- mov bx,ax ! Save for later
- mov stashed_ss, ax ! Save SS:SP
- mov ax,sp
- mov stashed_sp, ax
!
! Switch segments
!
- mov ax,stashed_ds ! Recover the data segment
- mov ds,ax
- mov es,ax
+ seg SEG_IRQ_DATA
+ mov bx,stashed_ds ! Recover the data segment
+ mov ds,bx
+
+ mov dx,ss ! Get current SS
+ mov bp,sp ! Get current SP
+ movb cl,bios_call_cnt_l
!
! Set up task switch controller
!
@@ -469,14 +468,13 @@
!
! See where we were (BX holds the SS on entry)
!
- cmp ax,bx ! SS = kernel SS ?
+ cmp dx,bx ! SS = kernel SS ?
je ktask ! Kernel - no work
!
! User or BIOS etc
!
- mov ax,bx
mov bx,_current
- cmp ax,4[bx] ! entry ss = current->t_regs.ss?
+ cmp dx,4[bx] ! entry ss = current->t_regs.ss?
je utask ! Switch to kernel
!
! Bios etc - switch to interrupt stack
@@ -488,37 +486,24 @@
! User task. Extract kernel SP. (BX already holds current)
!
utask:
- mov ax,[bx] ! kernel stack ptr
- mov sp,ax ! switch to kernel stack
+ mov sp,[bx] ! switch to kernel stack ptr
inc ch ! Switch allowable
- j switched
-ktask:
!
! In ktask state we have a suitable stack. It might be
! better to use the intstack..
!
switched:
- mov ax,ds
- mov ss,ax ! /* Set SS: right */
+ mov bx,ds
+ mov ss,bx ! /* Set SS: right */
+ktask:
+ mov es,bx ! /* Set ES: right */
! /*
! Put the old SS;SP on the top of the stack. We can't
! leave them in stashed_ss/sp as we could re-enter the
! routine on a reschedule.
! */
-#ifdef CONFIG_ROMCODE
- mov ax,#CONFIG_ROM_IRQ_DATA
- mov es,ax
- seg es
- push stashed_sp
- seg es
- push stashed_ss
-
-#else
- seg cs
- push stashed_sp
- seg cs
- push stashed_ss
-#endif
+ push bp ! push entry SP
+ push dx ! push entry SS
!
! We are on a suitable stack and cx says whether we can
! switch afterwards. The C code will want to eat CX so
@@ -530,19 +515,9 @@
mov bp,sp
mov _can_tswitch, ch
push cx ! Save ch
-#ifdef CONFIG_ROMCODE
- seg es
-#else
- seg cs ! Recover the IRQ we saved
-#endif
- mov ax,stashed_irq
push ax ! IRQ for later
push bp ! Register base
push ax ! IRQ number
-#ifdef CONFIG_ROMCODE
- mov ax,ds
- mov es,ax ;es back to dataseg
-#endif
!
! Call the C code
!
@@ -557,48 +532,22 @@
!
! Restore any chips
!
- cmp ax,#15
+ cmp ax,#16
jge was_trap ! Traps need no reset
- cmp ax,#8
- jge sec_8259 ! IRQ on low chip
-!
-! Reset primary 8259
-!
+ or ax,ax ! Is int #0?
+ jnz a4
+ dec cl ! Will call bios int?
+ je was_trap
+a4:
mov cl,al ! Save the IRQ number
- inb al,0x21 ! The chip line state
- jmp a7
-a7: jmp a8
-a8:
-! movb al,#1
-! shl al,cl ! Shift the irq (saved in cl) to a mask
-! orb al,_cache_21
-! movb _cache_21, al
- movb al,_cache_21 ! Extract the IRQ mask register
- outb 0x21,al ! Now ack the IRQ
- jmp a9
-a9: jmp a10
-a10: movb al,#0x20 ! EOI
- outb 0x20,al
- jmp was_trap
-
+ movb al,#0x20 ! EOI
+ cmp cl,#8
+ jb a6 ! IRQ on low chip
!
! Reset secondary 8259 if we have taken an AT rather
! than XT irq. We also have to prod the primay
! controller EOI..
!
-sec_8259:
- mov cl,al ! Save the IRQ for making masks
- inb al,0xA1
- jmp a1
-a1: jmp a2
-a2: movb al,#1
- shl al,cl
- orb al,_cache_A1
- movb _cache_A1, al
- outb 0xA1,al ! Now ack the IRQ
- jmp a3
-a3: jmp a4
-a4: movb al,#0x20
outb 0xA0,al
jmp a5
a5: jmp a6
@@ -609,6 +558,17 @@
!
was_trap:
+ orb cl,cl
+ jnz no_bios_call
+!
+! IRQ 0 (timer) has to go on to the bios for some systems
+!
+ dec bios_call_cnt_l
+ jne no_bios_call
+ mov bios_call_cnt_l,#5
+ pushf
+ callf off_stashed_irq0_l
+no_bios_call:
!
! Now look at rescheduling
!
@@ -655,83 +615,25 @@
pop cx
pop bx
pop es
-#ifdef CONFIG_ROMCODE
- mov ax,#CONFIG_ROM_IRQ_DATA
- mov ds,ax
-#else
- seg cs
-#endif
- mov ax, stashed_irq
- or ax,ax
- jz irq0_bios
pop ds
pop ax
!
! Iret restores CS:IP and F (thus including the interrupt bit)
!
iret
-!
-! IRQ 0 (timer) has to go on to the bios for some systems
-!
-! FIXME: should call the bios only every fifth event.
-!
-irq0_bios:
- pop ds
- pop ax ;now the stack empty
-
-;------------------------------------------------
-;Build new Stack
-;
-; SP -> RET seg
-; RET offs
-; SP-4 -> BP
-; SP-4 -> BX
-; DS
-; SP-8 -> free ;sp
-
-label1:
-
- sub sp,#4 ;space for retf
- push bp
- mov bp,sp
-
- push bx
- push ds
-#ifdef CONFIG_ROMCODE
- mov bx,#CONFIG_ROM_IRQ_DATA
-#else
- mov bx,cs
-#endif
- mov ds,bx
- mov bx,bios_call_cnt
- inc bx
- cmp bx,#5
- jne no_bios_call
-
- xor bx,bx
- mov bios_call_cnt,bx
- mov bx, seg_stashed_irq0
- mov [bp+4], bx
- mov bx, off_stashed_irq0
- mov [bp+2], bx
-
- pop ds
- pop bx
- pop bp
- retf
-
-no_bios_call: ;sp-8
- mov bios_call_cnt,bx
- pop ds
- pop bx ;sp-4
- pop bp
- add sp,#4
- iret
.data
.globl _can_tswitch
_can_tswitch:
.byte 0
+
+off_stashed_irq0_l:
+ .word 0
+seg_stashed_irq0_l:
+ .word 0
+bios_call_cnt_l:
+ .word 0
+
.zerow 256 ! (was) 128 byte interrupt stack
_intstack:
--
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