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SubjectRe: [PATCH] Check for breakpoint in text_poke to eliminate bug_on
On Sat, 19 Apr 2008 17:58:26 -0400
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> * Pekka Paalanen (pq@iki.fi) wrote:
> >
> > A simple
> > echo 0 > /sys/devices/system/cpu/cpu1/online
> > echo 1 > /sys/devices/system/cpu/cpu1/online
> >
> > produces the following kernel log (netconsole) and then after a couple
> > second hang the machine reboots:
> >
> > [ 84.678357] console [netcon0] enabled
> > [ 84.679568] netconsole: network logging started
> > [ 232.812335] CPU 1 is now offline
> > [ 232.812678] lockdep: fixing up alternatives.
> > [ 232.813051] SMP alternatives: switching to UP code
> > [ 268.447582] lockdep: fixing up alternatives.
> > [ 268.447903] SMP alternatives: switching to SMP code
> > [ 268.459462] Booting processor 1/1 ip 6000
> >
> > My kernel is sched-devel/latest git tree with Desnoyers' patch, and my
> > patches that touch only arch/x86/mm/mmio-mod.c.
> > The machine is Thinkpad T61 with:
> >
> > processor : 0
> > vendor_id : GenuineIntel
> > cpu family : 6
> > model : 15
> > model name : Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz
> > stepping : 10
> > cpu MHz : 2001.000
> > cache size : 4096 KB
> > physical id : 0
> > siblings : 2
> > core id : 0
> > cpu cores : 2
> > apicid : 0
> > initial apicid : 0
> > fpu : yes
> > fpu_exception : yes
> > cpuid level : 10
> > wp : yes
> > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
> > cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx
> > lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx est
> > tm2 ssse3 cx16 xtpr lahf_lm ida
> > bogomips : 3997.03
> > clflush size : 64
> > cache_alignment : 64
> > address sizes : 36 bits physical, 48 bits virtual
> > power management:
> >
> > processor : 1
> > vendor_id : GenuineIntel
> > cpu family : 6
> > model : 15
> > model name : Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz
> > stepping : 10
> > cpu MHz : 2001.000
> > cache size : 4096 KB
> > physical id : 0
> > siblings : 2
> > core id : 1
> > cpu cores : 2
> > apicid : 1
> > initial apicid : 1
> > fpu : yes
> > fpu_exception : yes
> > cpuid level : 10
> > wp : yes
> > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
> > cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx
> > lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx est
> > tm2 ssse3 cx16 xtpr lahf_lm ida
> > bogomips : 3991.26
> > clflush size : 64
> > cache_alignment : 64
> > address sizes : 36 bits physical, 48 bits virtual
> > power management:
> >
> > Any help would be appreciated.
> >
> >
> > Thanks.
>
> This patch should bring more consistency checks to text_poke, can you
> give it a try ?
>
> Hm, actually, I think it contains the fix you are looking for.
>
> kernel_text_address -> core_kernel_text will probably make everything go
> smoothly.
>
> Mathieu
>
>
> Check for breakpoint in text_poke to eliminate bug_on
>
> It's ok to modify an instruction non-atomically (multiple memory accesses to a
> large and/or non aligned instruction) *if and only if* we have inserted a
> breakpoint at the beginning of the instruction.
>
> Also change kernel_text_address (bogus) check to core_kernel_text.
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> ---
> arch/x86/kernel/alternative.c | 49 ++++++++++++++++++++++++------------------
> 1 file changed, 29 insertions(+), 20 deletions(-)

Sorry, no change.

[ 93.315242] netconsole: network logging started
[ 95.797496] eth0: no IPv6 routers present
[ 127.472213] CPU 1 is now offline
[ 127.472547] lockdep: fixing up alternatives.
[ 127.472923] SMP alternatives: switching to UP code
[ 134.709384] lockdep: fixing up alternatives.
[ 134.709701] SMP alternatives: switching to SMP code
[ 134.721344] Booting processor 1/1 ip 6000

few seconds pause and it reboots. A working patch in six minutes would
have been quite awesome :-)


Thanks.

--
Pekka Paalanen
http://www.iki.fi/pq/


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