Re: Patch "page-allocator: preserve PFN ordering when __GFP_COLD

[Mel Gorman <mel@csn.ul.ie>]

On Wed, Aug 12, 2009 at 09:47:53AM +0200, Robert Schwebel wrote:
> Hi Jürgen,
> 
> adding the patch author to Cc: ...
> 
> rsc
> 
> On Tue, Aug 11, 2009 at 06:30:02PM +0200, Juergen Beisert wrote:
> > Hi,
> > 
> > I get the following Ooops message when "udevadm" is running on an ARM S3C2440
> > CPU based system:
> > 

This is extremely odd. All that patch is doing is changing what order pages
are returned in to the caller when __GFP_COLD is specified.  valid memory. Does
reverting the patch really make the problem go away?

> > [...]
> > starting udevd...done
> > Unable to handle kernel paging request at virtual address e3540000
> > pgd = c39d4000
> > [e3540000] *pgd\0000000
> > Internal error: Oops: 5 [#1]
> > Modules linked in:
> > CPU: 0    Not tainted  (2.6.31-rc4-00296-ge084b2d-dirty #10)
> > PC is at strlen+0xc/0x20
> > LR is at kobject_get_path+0x24/0xa4

I haven't tackled this sort of bug before but it looks more likely that
there is garbage in the sysfs tree that is being tripped up on.

> > pc : [<c0115338>]    lr : [<c0111f48>]    psr: a0000013
> > sp : c39bdea0  ip : 00000005  fp : c029645b
> > r10: c02e0430  r9 : 00000000  r8 : c3802c60
> > r7 : c001de30  r6 : 000000d0  r5 : 00000001  r4 : c001de30
> > r3 : e3550001  r2 : e3540000  r1 : 000000d0  r0 : e3540000
> > Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
> > Control: c000717f  Table: 339d4000  DAC: 00000015
> > Process udevadm (pid: 325, stack limit = 0xc39bc270)
> > Stack: (0xc39bdea0 to 0xc39be000)
> > dea0: c001de28 00000003 c393d778 c399d000 c3802c60 c014dce0 c029645b c0112200
> > dec0: c393d778 00000000 00000003 c393d780 c399d000 c0112400 00000000 00020001
> > dee0: c0307fdc 00000000 c3950960 c027ddc3 c380cda0 c343b3d4 c3811e60 00000000
> > df00: 00000000 c393d778 00000003 c3960520 c393d780 c02e0470 c3960538 c39bdf88
> > df20: 00019cb0 c014dd80 c382db20 00000000 c3960538 c38ede7c 00000003 c014d464
> > df40: c38ede7c c00bf224 c382db20 00019cb0 c39bdf88 00000004 00000003 c39bc000
> > df60: 00000000 c0080bd8 c343b3d4 00000020 00000000 00000000 c382db20 00000004
> > df80: c0022fa8 c0080d38 00000000 00000000 bead3250 00000000 00026d98 00000003
> > dfa0: bead3250 c0022e00 00026d98 00000003 00000003 00019cb0 00000003 00000000
> > dfc0: 00026d98 00000003 bead3250 00000004 00022a90 bead3678 00019cb0 00019cb0
> > dfe0: 00022a94 bead3250 00018114 400d8f1c 40000010 00000003 00000000 00000000
> > [<c0115338>] (strlen+0xc/0x20) from [<c0111f48>] (kobject_get_path+0x24/0xa4)
> > [<c0111f48>] (kobject_get_path+0x24/0xa4) from [<c014dce0>] (dev_uevent+0x1dc/0x208)
> > [<c014dce0>] (dev_uevent+0x1dc/0x208) from [<c0112400>] (kobject_uevent_env+0x18c/0x3a8)
> > [<c0112400>] (kobject_uevent_env+0x18c/0x3a8) from [<c014dd80>] (store_uevent+0x74/0x88)
> > [<c014dd80>] (store_uevent+0x74/0x88) from [<c014d464>] (dev_attr_store+0x20/0x28)
> > [<c014d464>] (dev_attr_store+0x20/0x28) from [<c00bf224>] (sysfs_write_file+0x104/0x13c)
> > [<c00bf224>] (sysfs_write_file+0x104/0x13c) from [<c0080bd8>] (vfs_write+0xb0/0x15c)
> > [<c0080bd8>] (vfs_write+0xb0/0x15c) from [<c0080d38>] (sys_write+0x40/0x6c)
> > [<c0080d38>] (sys_write+0x40/0x6c) from [<c0022e00>] (ret_fast_syscall+0x0/0x2c)
> > Code: c02dbe78 e1a02000 ea000000 e2800001 (e5d03000)
> > ---[ end trace 4d391449ae70e71a ]---
> > Segmentation fault
> > [...]
> > 
> > This Oops does not occure in v2.6.31-rc4 and occures in v2.6.31-rc5. Bisected
> > to the commit:
> > 
> > e084b2d95e48b31aa45f9c49ffc6cdae8bdb21d4
> > "page-allocator: preserve PFN ordering when __GFP_COLD is set"
> > 
> > But its curious: The same binary kernel still runs without this oops on an ARM
> > S3C2410 CPU.
> > 
> > Regards,
> > Juergen
> > 
> > -- 
> > Pengutronix e.K.                              | Juergen Beisert             |
> > Linux Solutions for Science and Industry      | Phone: +49-8766-939 228     |
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> 
> -- 
> Pengutronix e.K.                           |                             |
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-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab