On Fri, 15 Aug 2008, Al Viro wrote: > On Thu, Aug 14, 2008 at 07:31:06PM +0100, Hugh Dickins wrote: > > I got this oops below, after several hours of swap-heavy kernel builds > > in tmpfs, on 2.6.27-rc1-mm1 a couple of weeks ago. Tried to reproduce > > it without success, then got a very similar trace (not saved) from > > 2.6.27-rc3 itself doing the same test yesterday: again oopsing in > > proc_sys_compare on address -16, looks like it's trying for > > PROC_I(dentry->d_inode)->sysctl but d_inode is NULL. > > > > I looked to see what's been going on in fs/proc recently, and your > > [PATCH] sanitize proc_sysctl 9043476f726802f4b00c96d0c4f418dde48d1304 > > does sound like it might be implicated. I've only seen this on > > PowerPC G5, similar tests on x86_32 and _64 haven't shown it: > > maybe a memory barrier needed somewhere? > > Bloody interesting. We never create negative hashed dentries in there and > AFAICS we should never get d_delete() called on those... Missing barrier > would mean serious trouble in dcache.c and not just for /proc/sys... > > Are you sure about oops decoding? At least disassembly of proc_sys_compare() > in the kernel image in question would be nice to see...
Here it is: I'd changed config meanwhile, so this is from a rebuild, but symbol addresses fit exactly with the trace (and the 2.6.27-rc1-mm1 fs/proc/proc_sysctl.c is identical to that in 2.6.27-rc3 or current git). I did try "objdump -Sd" at first, but that just looked more confusing. c000000000121e7c <.proc_sys_compare>: proc_sys_compare(): /home/hugh/26271E1/fs/proc/proc_sysctl.c:383 c000000000121e7c: 7c 08 02 a6 mflr r0 c000000000121e80: fb e1 ff f0 std r31,-16(r1) c000000000121e84: 7c a9 2b 78 mr r9,r5 c000000000121e88: 7c 9f 23 78 mr r31,r4 c000000000121e8c: f8 01 00 10 std r0,16(r1) c000000000121e90: f8 21 ff 81 stdu r1,-128(r1) /home/hugh/26271E1/fs/proc/proc_sysctl.c:385 c000000000121e94: 60 00 00 00 nop c000000000121e98: 80 a4 00 04 lwz r5,4(r4) c000000000121e9c: 80 09 00 04 lwz r0,4(r9) c000000000121ea0: 7f 80 28 00 cmpw cr7,r0,r5 c000000000121ea4: 40 9e 00 3c bne- cr7,c000000000121ee0 <.proc_sys_compare+0x64> /home/hugh/26271E1/fs/proc/proc_sysctl.c:387 c000000000121ea8: e8 89 00 08 ld r4,8(r9) c000000000121eac: e8 7f 00 08 ld r3,8(r31) c000000000121eb0: 4b f0 aa 45 bl c00000000002c8f4 <.memcmp> c000000000121eb4: 60 00 00 00 nop c000000000121eb8: 2f a3 00 00 cmpdi cr7,r3,0 c000000000121ebc: 40 9e 00 24 bne- cr7,c000000000121ee0 <.proc_sys_compare+0x64> PROC_I(): /home/hugh/26271E1/fs/proc/proc_sysctl.c:384 c000000000121ec0: e9 3f ff e0 ld r9,-32(r31) c000000000121ec4: e8 69 ff f0 ld r3,-16(r9) c000000000121ec8: 4b f2 f8 4d bl c000000000051714 <.sysctl_is_seen> c000000000121ecc: 60 00 00 00 nop proc_sys_compare(): /home/hugh/26271E1/fs/proc/proc_sysctl.c:389 c000000000121ed0: 7c 63 00 34 cntlzw r3,r3 c000000000121ed4: 54 63 d9 7e rlwinm r3,r3,27,5,31 c000000000121ed8: 78 63 00 20 clrldi r3,r3,32 c000000000121edc: 48 00 00 08 b c000000000121ee4 <.proc_sys_compare+0x68> c000000000121ee0: 38 60 00 01 li r3,1 /home/hugh/26271E1/fs/proc/proc_sysctl.c:390 c000000000121ee4: 38 21 00 80 addi r1,r1,128 c000000000121ee8: e8 01 00 10 ld r0,16(r1) c000000000121eec: eb e1 ff f0 ld r31,-16(r1) c000000000121ef0: 7c 08 03 a6 mtlr r0 c000000000121ef4: 4e 80 00 20 blr _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
