PPC upstream kernel ignored DABR bug

[Roland McGrath]

> Since the 970 kernel never sets DABRX currently, #8 cannot explain
> _intermittent_ problems: either it always works, or never does.

That's kind of what I thought, but I couldn't make enough sense of
the #8 text to be very sure.

> You could be happening upon #5, if the non-triggering data breakpoints
> are with vector loads/stores in strange code.

They are not.

> It would help if you could give us the disassembly of some code where the
> breakpoint did not trigger; say, that insn and the previous 20 or so insns.

The pointer to the test case was given here before.

http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/tests/ptrace-tests/tests/ppc-dabr-race.c?cvsroot=systemtap

-m32	Dump of assembler code for function child_thread:
	0x10000950 <child_thread+0>:    stwu    r1,-32(r1)
	0x10000954 <child_thread+4>:    li      r3,207
	0x10000958 <child_thread+8>:    mflr    r0
	0x1000095c <child_thread+12>:   stw     r29,20(r1)
	0x10000960 <child_thread+16>:   stw     r0,36(r1)
	0x10000964 <child_thread+20>:   crclr   4*cr1+eq
	0x10000968 <child_thread+24>:   bl      0x10001680 <syscall>
	0x1000096c <child_thread+28>:   lis     r11,4097
	0x10000970 <child_thread+32>:   mr      r29,r3
	0x10000974 <child_thread+36>:   li      r3,1
	0x10000978 <child_thread+40>:   lwz     r9,7800(r11)
	0x1000097c <child_thread+44>:   addi    r9,r9,1
	0x10000980 <child_thread+48>:   stw     r9,7800(r11)
	0x10000984 <child_thread+52>:   bl      0x10001750 <sleep>
	0x10000988 <child_thread+56>:   lis     r9,4097
--->	0x1000098c <child_thread+60>:   stw     r29,7792(r9)
	0x10000990 <child_thread+64>:   bl      0x10001760 <pause>
	0x10000994 <child_thread+68>:   bl      0x10001760 <pause>
	0x10000998 <child_thread+72>:   b       0x10000990 <child_thread+64>
	End of assembler dump.

-m64	Dump of assembler code for function child_thread:
	0x0000000010000d10 <child_thread+0>:    mflr    r0
	0x0000000010000d14 <child_thread+4>:    std     r29,-24(r1)
	0x0000000010000d18 <child_thread+8>:    li      r3,207
	0x0000000010000d1c <child_thread+12>:   std     r0,16(r1)
	0x0000000010000d20 <child_thread+16>:   stdu    r1,-144(r1)
	0x0000000010000d24 <child_thread+20>:   bl      0x10000b68
	0x0000000010000d28 <child_thread+24>:   ld      r2,40(r1)
	0x0000000010000d2c <child_thread+28>:   ld      r11,-32696(r2)
	0x0000000010000d30 <child_thread+32>:   mr      r29,r3
	0x0000000010000d34 <child_thread+36>:   li      r3,1
	0x0000000010000d38 <child_thread+40>:   extsw   r29,r29
	0x0000000010000d3c <child_thread+44>:   lwz     r9,0(r11)
	0x0000000010000d40 <child_thread+48>:   addi    r9,r9,1
	0x0000000010000d44 <child_thread+52>:   clrldi  r9,r9,32
	0x0000000010000d48 <child_thread+56>:   stw     r9,0(r11)
	0x0000000010000d4c <child_thread+60>:   bl      0x10000a88
	0x0000000010000d50 <child_thread+64>:   ld      r2,40(r1)
	0x0000000010000d54 <child_thread+68>:   ld      r9,-32688(r2)
--->	0x0000000010000d58 <child_thread+72>:   std     r29,0(r9)
	0x0000000010000d5c <child_thread+76>:   nop
	0x0000000010000d60 <child_thread+80>:   bl      0x100009a8
	0x0000000010000d64 <child_thread+84>:   ld      r2,40(r1)
	0x0000000010000d68 <child_thread+88>:   b       0x10000d60 <child_thread+80>
	0x0000000010000d6c <child_thread+92>:   .long 0x0
	0x0000000010000d70 <child_thread+96>:   .long 0x1
	0x0000000010000d74 <child_thread+100>:  lwz     r0,0(r3)
	End of assembler dump.


Thanks,
Roland