On Wed, 20 Aug 2008, Eran Liberty wrote: > Steven Rostedt wrote: > > On Wed, 20 Aug 2008, Steven Rostedt wrote: > > > > > > > On Wed, 20 Aug 2008, Benjamin Herrenschmidt wrote: > > > > > > > > > > Found the problem (or at least -a- problem), it's a gcc bug. > > > > > > > > Well, first I must say the code generated by -pg is just plain > > > > horrible :-) > > > > > > > > Appart from that, look at the exit of, for example, __d_lookup, as > > > > generated by gcc when ftrace is enabled: > > > > > > > > c00c0498: 38 60 00 00 li r3,0 > > > > c00c049c: 81 61 00 00 lwz r11,0(r1) > > > > c00c04a0: 80 0b 00 04 lwz r0,4(r11) > > > > c00c04a4: 7d 61 5b 78 mr r1,r11 > > > > c00c04a8: bb 0b ff e0 lmw r24,-32(r11) > > > > c00c04ac: 7c 08 03 a6 mtlr r0 > > > > c00c04b0: 4e 80 00 20 blr > > > > > > > > As you can see, it restores r1 -before- it pops r24..r31 off > > > > the stack ! I let you imagine what happens if an interrupt happens > > > > just in between those two instructions (mr and lmw). We don't do > > > > redzones on our ABI, so basically, the registers end up corrupted > > > > by the interrupt. > > > > > > > Ouch! You've disassembled this without -pg too, and it does not have this > > > bug? What version of gcc do you have? > > > > > > > > > > I have: > > gcc (Debian 4.3.1-2) 4.3.1 > > > > c00c64c8: 81 61 00 00 lwz r11,0(r1) > > c00c64cc: 7f 83 e3 78 mr r3,r28 > > c00c64d0: 80 0b 00 04 lwz r0,4(r11) > > c00c64d4: ba eb ff dc lmw r23,-36(r11) > > c00c64d8: 7d 61 5b 78 mr r1,r11 > > c00c64dc: 7c 08 03 a6 mtlr r0 > > c00c64e0: 4e 80 00 20 blr > > > > > > My version looks fine. I'm thinking that this is a separate issue than what > > Eran is seeing. > > > > Eran, can you do an "objdump -dr vmlinux" and search for __d_lookup, and > > print out the end of the function dump. > > > > Thanks, > > > > -- Steve > > > > > > > > > powerpc-linux-gnu-objdump -dr --start-address=0xc00bb584 vmlinux | head -n 100 > > vmlinux: file format elf32-powerpc > > Disassembly of section .text: > > c00bb584 <__d_lookup>:
[...] > c00bb670: 41 9e 00 50 beq- cr7,c00bb6c0 <__d_lookup+0x13c> > c00bb674: 83 de 00 00 lwz r30,0(r30) > c00bb678: 2f 9e 00 00 cmpwi cr7,r30,0 > c00bb67c: 40 9e ff 98 bne+ cr7,c00bb614 <__d_lookup+0x90> > c00bb680: 38 60 00 00 li r3,0 > c00bb684: 81 61 00 00 lwz r11,0(r1) > c00bb688: 80 0b 00 04 lwz r0,4(r11) > c00bb68c: 7d 61 5b 78 mr r1,r11 [ BUG HERE IF INTERRUPT HAPPENS ] > c00bb690: bb 0b ff e0 lmw r24,-32(r11) > c00bb694: 7c 08 03 a6 mtlr r0 > c00bb698: 4e 80 00 20 blr Yep, you have the same bug in your compiler. -- Steve _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
