GIE disables itself - AS6

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InHuMan
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Posted by InHuMan: Mon. Nov 12, 2012 - 12:04 AM
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Hi,
I have a problem with my program. Global Interrupts disables itself.
I am using Atmel Studio 6 SP1 with latest tool-chain (Version: 3.4.1.798 - GCC 4.6.2) and default project settings. Target CPU is ATmega16.
I've managed to isolate the problem in this simple test case:
Interrupts are disabled by BufferAdd function, the question is why? :-(
Thanks for your help.

#include 
#include 

typedef struct
{
	uint8_t address;
	uint8_t data[5];

} Message;

typedef struct
{
	Message mess[4];
	uint8_t Head;
	uint8_t Tail;
} TransmitBufer ;

TransmitBufer buff;


void BufferAdd(Message msg)
{
	buff.Head++;
	buff.mess[buff.Head] = msg;
}

int main(void)
{
	sei(); //Interrupts are enabled
	
	Message msg;
	BufferAdd(msg); //GIE disables itself here!
	
	while(1)
	{
		asm volatile ("nop"); 
	}
}

Tags:

Tools, Compilers and General Programming, ATmega16
Last Edited: Mon. Nov 12, 2012 - 12:42 PM
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skeeve
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Posted by skeeve: Mon. Nov 12, 2012 - 12:27 AM
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How can you tell?
What does the asm tell you?

Moderation in all things. -- ancient proverb

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gregd99
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Posted by gregd99: Mon. Nov 12, 2012 - 04:08 AM
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be aware that there is a bug in as6 where single stepping over sei() causes a problem.

if you are having this problem try setting a breakpoint at BufferAdd(msg) rather than stepping to it.

regards
Greg

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Gold Markclawson
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Posted by clawson: Mon. Nov 12, 2012 - 09:12 AM
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I just built and simulated that for mega16 in AS6 1938 + 3.4.1 and did two "Step-over"s and I was still set when it reached the asm() in the while(). So exactly what are you doing to see this effect?

(as already noted AS6 has issue with the simulated execution of SEI).

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InHuMan
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Posted by InHuMan: Mon. Nov 12, 2012 - 09:50 AM
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skeeve wrote:
How can you tell?
What does the asm tell you?

Well, I am not an asm expert, but here is lss file (default debug build):
I thing, that there should not be cli instruction in BufferAdd function.

test1.elf:     file format elf32-avr

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00000112  00000000  00000000  00000094  2**1
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .data         00000000  00800060  00000112  000001a6  2**0
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          0000001a  00800060  00800060  000001a6  2**0
                  ALLOC
  3 .stab         000006cc  00000000  00000000  000001a8  2**2
                  CONTENTS, READONLY, DEBUGGING
  4 .stabstr      00000085  00000000  00000000  00000874  2**0
                  CONTENTS, READONLY, DEBUGGING
  5 .debug_aranges 00000060  00000000  00000000  00000900  2**3
                  CONTENTS, READONLY, DEBUGGING
  6 .debug_info   00000297  00000000  00000000  00000960  2**0
                  CONTENTS, READONLY, DEBUGGING
  7 .debug_abbrev 0000003c  00000000  00000000  00000bf7  2**0
                  CONTENTS, READONLY, DEBUGGING
  8 .debug_line   000001a7  00000000  00000000  00000c33  2**0
                  CONTENTS, READONLY, DEBUGGING

Disassembly of section .text:

00000000 <__vectors>:
   0:	0c 94 2a 00 	jmp	0x54	; 0x54 <__ctors_end>
   4:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
   8:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
   c:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  10:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  14:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  18:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  1c:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  20:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  24:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  28:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  2c:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  30:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  34:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  38:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  3c:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  40:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  44:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  48:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  4c:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>
  50:	0c 94 47 00 	jmp	0x8e	; 0x8e <__bad_interrupt>

00000054 <__ctors_end>:
  54:	11 24       	eor	r1, r1
  56:	1f be       	out	0x3f, r1	; 63
  58:	cf e5       	ldi	r28, 0x5F	; 95
  5a:	d4 e0       	ldi	r29, 0x04	; 4
  5c:	de bf       	out	0x3e, r29	; 62
  5e:	cd bf       	out	0x3d, r28	; 61

00000060 <__do_copy_data>:
  60:	10 e0       	ldi	r17, 0x00	; 0
  62:	a0 e6       	ldi	r26, 0x60	; 96
  64:	b0 e0       	ldi	r27, 0x00	; 0
  66:	e2 e1       	ldi	r30, 0x12	; 18
  68:	f1 e0       	ldi	r31, 0x01	; 1
  6a:	02 c0       	rjmp	.+4      	; 0x70 <__do_copy_data+0x10>
  6c:	05 90       	lpm	r0, Z+
  6e:	0d 92       	st	X+, r0
  70:	a0 36       	cpi	r26, 0x60	; 96
  72:	b1 07       	cpc	r27, r17
  74:	d9 f7       	brne	.-10     	; 0x6c <__do_copy_data+0xc>

00000076 <__do_clear_bss>:
  76:	10 e0       	ldi	r17, 0x00	; 0
  78:	a0 e6       	ldi	r26, 0x60	; 96
  7a:	b0 e0       	ldi	r27, 0x00	; 0
  7c:	01 c0       	rjmp	.+2      	; 0x80 <.do_clear_bss_start>

0000007e <.do_clear_bss_loop>:
  7e:	1d 92       	st	X+, r1

00000080 <.do_clear_bss_start>:
  80:	aa 37       	cpi	r26, 0x7A	; 122
  82:	b1 07       	cpc	r27, r17
  84:	e1 f7       	brne	.-8      	; 0x7e <.do_clear_bss_loop>
  86:	0e 94 75 00 	call	0xea	; 0xea 

  8a:	0c 94 87 00 	jmp	0x10e	; 0x10e <_exit>

0000008e <__bad_interrupt>:
  8e:	0c 94 00 00 	jmp	0	; 0x0 <__vectors>

00000092 :
  92:	cf 93       	push	r28
  94:	df 93       	push	r29
  96:	00 d0       	rcall	.+0      	; 0x98 
  98:	00 d0       	rcall	.+0      	; 0x9a 
  9a:	00 d0       	rcall	.+0      	; 0x9c 
  9c:	cd b7       	in	r28, 0x3d	; 61
  9e:	de b7       	in	r29, 0x3e	; 62
  a0:	49 83       	std	Y+1, r20	; 0x01
  a2:	5a 83       	std	Y+2, r21	; 0x02
  a4:	6b 83       	std	Y+3, r22	; 0x03
  a6:	7c 83       	std	Y+4, r23	; 0x04
  a8:	8d 83       	std	Y+5, r24	; 0x05
  aa:	9e 83       	std	Y+6, r25	; 0x06
  ac:	80 91 78 00 	lds	r24, 0x0078
  b0:	8f 5f       	subi	r24, 0xFF	; 255
  b2:	80 93 78 00 	sts	0x0078, r24
  b6:	90 e0       	ldi	r25, 0x00	; 0
  b8:	fc 01       	movw	r30, r24
  ba:	ee 0f       	add	r30, r30
  bc:	ff 1f       	adc	r31, r31
  be:	e8 0f       	add	r30, r24
  c0:	f9 1f       	adc	r31, r25
  c2:	ee 0f       	add	r30, r30
  c4:	ff 1f       	adc	r31, r31
  c6:	e0 5a       	subi	r30, 0xA0	; 160
  c8:	ff 4f       	sbci	r31, 0xFF	; 255
  ca:	de 01       	movw	r26, r28
  cc:	11 96       	adiw	r26, 0x01	; 1
  ce:	86 e0       	ldi	r24, 0x06	; 6
  d0:	0d 90       	ld	r0, X+
  d2:	01 92       	st	Z+, r0
  d4:	81 50       	subi	r24, 0x01	; 1
  d6:	e1 f7       	brne	.-8      	; 0xd0 
  d8:	26 96       	adiw	r28, 0x06	; 6
  da:	0f b6       	in	r0, 0x3f	; 63
  dc:	f8 94       	cli
  de:	de bf       	out	0x3e, r29	; 62
  e0:	0f be       	out	0x3f, r0	; 63
  e2:	cd bf       	out	0x3d, r28	; 61
  e4:	df 91       	pop	r29
  e6:	cf 91       	pop	r28
  e8:	08 95       	ret

000000ea 
:
  ea:	cf 93       	push	r28
  ec:	df 93       	push	r29
  ee:	00 d0       	rcall	.+0      	; 0xf0 
  f0:	00 d0       	rcall	.+0      	; 0xf2 
  f2:	00 d0       	rcall	.+0      	; 0xf4 
  f4:	cd b7       	in	r28, 0x3d	; 61
  f6:	de b7       	in	r29, 0x3e	; 62
  f8:	78 94       	sei
  fa:	49 81       	ldd	r20, Y+1	; 0x01
  fc:	5a 81       	ldd	r21, Y+2	; 0x02
  fe:	6b 81       	ldd	r22, Y+3	; 0x03
 100:	7c 81       	ldd	r23, Y+4	; 0x04
 102:	8d 81       	ldd	r24, Y+5	; 0x05
 104:	9e 81       	ldd	r25, Y+6	; 0x06
 106:	0e 94 49 00 	call	0x92	; 0x92 
 10a:	00 00       	nop
 10c:	fe cf       	rjmp	.-4      	; 0x10a 

0000010e <_exit>:
 10e:	f8 94       	cli

00000110 <__stop_program>:
 110:	ff cf       	rjmp	.-2      	; 0x110 <__stop_program>

gregd99 wrote:
be aware that there is a bug in as6 where single stepping over sei() causes a problem.

if you are having this problem try setting a breakpoint at BufferAdd(msg) rather than stepping to it.


Where can I find more about this bug? Is it only in simulator? My problem is in real hardware also (ATmega16 with JTAGICE3)

clawson wrote:
I just built and simulated that for mega16 in AS6 1938 + 3.4.1 and did two "Step-over"s and I was still set when it reached the asm() in the while(). So exactly what are you doing to see this effect?

Hmm, two "Step-over"s works fine, but more will disable GIE.
Another way to reproduce:
1, Put breakpoint at line. "BufferAdd(msg); //GIE disables itself here!"
2, Start debuging, programs breaks at break point - GIE is enabled
3, step into - GIE disabled... :-( (In simulator it takes 2 step into)
3b, "step over" works fine, but after second "step over" GIE is also disabled

It happened in simulator and over JTAG with JTAGICE3

Last Edited: Mon. Nov 12, 2012 - 10:53 AM
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Gold Markclawson
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Posted by clawson: Mon. Nov 12, 2012 - 10:23 AM
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Quote:

there should not be cli instruction in BufferAdd function

yes there should - it's protection while the (double register) stack pointer is being changed. Suppose the code had only changed one half of SPL/SPH and an interrupt occurred - it could be fatal! If you see the source generated for your code:

	adiw r28,6	 ; ,
	in __tmp_reg__,__SREG__
	cli
	out __SP_H__,r29	 ; 
	out __SREG__,__tmp_reg__
	out __SP_L__,r28	 ; 
	pop r29	 ; 
	pop r28	 ; 
	ret

you can see exactly what the compiler is up to. It's adjusting the stack back up by 6 bytes so it adds 6 to R29:R28 which now hold the new stack value. It then reads SREG to __tmp_reg__ (that is R0) and disables interrupts. It then starts to store the newly adjusted (by 6 bytes) stack value. It stores one half to SPH. It may seem odd that it then does an OUT to put SREG back the way it was but this is relying on a feature of the AVR that the change will not come into effect until one opcode later. So it then stores SPL with the new value and it's at the end of that opcode that the change to SREG comes into effectso I is now back the way it was when originally copied into __temp_reg__. Finally it recovers R29:R28 (also known as "Y") which is the stack frame pointer and it returns.

All this is completely normal and exactly what you would expect.

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InHuMan
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Posted by InHuMan: Mon. Nov 12, 2012 - 10:48 AM
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clawson wrote:
Quote:

there should not be cli instruction in BufferAdd function

yes there should - it's protection while the (double register) stack pointer is being changed.

Ohh, you are right. I can see it now. 0x3f is SREG address, so GIE state is restored after cli.
Well that means that this is not GCC bug, but AS6 bug. Stepping just does not work. Workaround is moving through code just using breakpoints.

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Gold Markclawson
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Posted by clawson: Mon. Nov 12, 2012 - 11:31 AM
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Quote:

but AS6 bug. Stepping just does not work. Workaround is moving through code just using breakpoints.

Indeed - that's what Greg told you above - it's a well know fault in AS6's simulator - it cannot step over an SEI.

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InHuMan
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Posted by InHuMan: Mon. Nov 12, 2012 - 11:48 AM
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clawson wrote:
Quote:

but AS6 bug. Stepping just does not work. Workaround is moving through code just using breakpoints.

Indeed - that's what Greg told you above - it's a well know fault in AS6's simulator - it cannot step over an SEI.

not only in simulator, but even with JTAGICE3. And not only at sei instruction, but in whole program

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abcminiuser
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Posted by abcminiuser: Mon. Nov 12, 2012 - 01:27 PM
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The SEI bug in the sim/tools should be corrected in the latest patch release of Atmel Studio - update from the extension manager.

- Dean :twisted:

Make Atmel Studio better with my free extensions. Open source and feedback welcome!

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InHuMan
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Posted by InHuMan: Mon. Nov 12, 2012 - 02:47 PM
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abcminiuser wrote:
The SEI bug in the sim/tools should be corrected in the latest patch release of Atmel Studio - update from the extension manager.

- Dean :twisted:


I already have latest version (at least I thing). I installed AS6, then SP1 and then updated avrgcc with extension manager.

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Bronze Markdavid.prentice
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Posted by david.prentice: Mon. Nov 12, 2012 - 03:28 PM
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Well, I tried it with a mega324PA. It worked fine with a Dragon and it worked fine with the Simulator.

David.

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InHuMan
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Posted by InHuMan: Mon. Nov 12, 2012 - 08:14 PM
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I copied project to different PC and it works! This is really strange because all installed packages versions in both PC match. :evil: (in help -> about atmel studio)
So I am trying to reinstall AS now.
Update: I applied SP1 and problem is still same (can't update to leatest toolchain through extension manager because Atmel update pages are down :evil: )

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gregd99
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Posted by gregd99: Mon. Nov 12, 2012 - 11:53 PM
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I had some unexplained behaviours when I installed on win7 without runas admin. even though my account had admin privilege this seemed to make a difference. just a suggestion.

regards
Greg

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InHuMan
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Posted by InHuMan: Tue. Nov 13, 2012 - 06:34 AM
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gregd99 wrote:
I had some unexplained behaviours when I installed on win7 without runas admin. even though my account had admin privilege this seemed to make a difference. just a suggestion.

Thanks, but this is probably not my case, because I have just one default account on both PCs. Both are Win7.

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drnicolas
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Posted by drnicolas: Tue. Nov 13, 2012 - 07:16 AM
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Do you have any ideas how to correct this problem ?
I spent nearly whole of the weekend, because my code sometimes reaches interrupt-service-routines and sometimes not.
E.g. I stepped through the code sending data via SPI and never got a SPI-ready-IRQ.
Yesterday i found out that the Global-Interrupt flag is de-activated sometimes without intention. This happens with real-hardware (at90CAN128, AVR Dragon AS6.1938)

I program like a man:
COPY CON: > firmware.hex

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Gold Markclawson
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Posted by clawson: Tue. Nov 13, 2012 - 09:21 AM
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Quote:

Yesterday i found out that the Global-Interrupt flag is de-activated sometimes without intention. This happens with real-hardware (at90CAN128, AVR Dragon AS6.1938)

But does it really happen in the hardware or is it a fault in the debugger. If you forget the debugger and instead send SREG as hex digits over the UART or an LCD from time to time is the bit really reset? I don't think it will be.

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drnicolas
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Posted by drnicolas: Tue. Nov 13, 2012 - 09:33 AM
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As I wrote before:

Single-Stepping into my subroutine disables the I-Flag. For me it seems that teh I-Flag then stays disabled.
Inmy case this affects CAN: Inside the subroutine a CAN-Message is sent, but the according ISR is then never reached.

The same happened to SPI-complete ISR.

I program like a man:
COPY CON: > firmware.hex

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drnicolas
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Posted by drnicolas: Tue. Nov 13, 2012 - 09:34 AM
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I am sorry, I don't have UART at this layout.

I program like a man:
COPY CON: > firmware.hex

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Gold Markclawson
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Posted by clawson: Tue. Nov 13, 2012 - 09:49 AM
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Yes but it's already been established that the debugger cannot handle single stepping over opcodes that change I so avoid doing that. Use breakpoints and "run to" instead.

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InHuMan
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Posted by InHuMan: Tue. Nov 13, 2012 - 10:28 PM
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clawson wrote:
Yes but it's already been established that the debugger cannot handle single stepping over opcodes that change I so avoid doing that. Use breakpoints and "run to" instead.

Well, I have one PC where everything is working fine (as far as I can tell) and one where it does not. Only difference is that working PC uses 32b version of windows 7. (installed in virtual box) So maybe it is just problem of 64b windows? Does anyone else experiencing this problem at 32b windows?

Update: I discovered there is an option in: Tool -> Options -> Debugger -> "Mask interrupts while stepping"
Try to change this to false.

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