Messages in this thread | | | Date | Sun, 20 Apr 2008 16:25:33 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH] Check for breakpoint in text_poke to eliminate bug_on |
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* Pekka Paalanen (pq@iki.fi) wrote: > On Sun, 20 Apr 2008 15:44:40 -0400 > Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote: > > > Can you test this new version ? The check was buggy when it fell on a > > code boundary : the addr - 1 wan't always a valid address. > > > > Sorry, still the same. Btw. I had to apply your patch by hand on top of > your previous patch, and it ended up as just > > --- a/arch/x86/kernel/alternative.c > +++ b/arch/x86/kernel/alternative.c > @@ -520,11 +520,6 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len) > struct page *pages[2]; > int i; > > - if (*((uint8_t *)addr - 1) != BREAKPOINT_INSTRUCTION) { > - BUG_ON(len > sizeof(long)); > - BUG_ON((((long)addr + len - 1) & ~(sizeof(long) - 1)) > - - ((long)addr & ~(sizeof(long) - 1))); > - } > if (!core_kernel_text((unsigned long)addr)) { > > Now I took a log of echo 0, echo 1 cycle with 2.6.24-gentoo-r1-trace > kernel: > [ 203.448534] CPU 1 is now offline > [ 203.448975] SMP alternatives: switching to UP code > [ 217.888298] SMP alternatives: switching to SMP code > [ 217.889285] Booting processor 1/2 APIC 0x1 > [ 217.901404] Initializing CPU#1 > [ 217.982081] Calibrating delay using timer specific routine.. 3991.35 BogoMIPS (lpj=6650167) > [ 217.982088] CPU: L1 I cache: 32K, L1 D cache: 32K > [ 217.982089] CPU: L2 cache: 4096K > [ 217.982091] CPU: Physical Processor ID: 0 > [ 217.982092] CPU: Processor Core ID: 1 > [ 217.982593] Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz stepping 0a > [ 217.982644] Switched to high resolution mode on CPU 1 > > And the failing log from the latest try is: > > [ 87.064970] CPU 1 is now offline > [ 87.065311] lockdep: fixing up alternatives. > [ 87.065694] SMP alternatives: switching to UP code > [ 97.192213] lockdep: fixing up alternatives. > [ 97.192532] SMP alternatives: switching to SMP code > [ 97.203495] Booting processor 1/1 ip 6000 > and it hangs and reboots. > > Does it make sense to bisect on sched-devel/latest? > I think I could try that after a sleep&work cycle. > Luckily this bug is easy to reproduce. >
Yup. I was able to successfully cycle cpu hotplug with 2.6.25 mainline with the equivalent of the text_poke patches I sent to you, therefore I guess it rules out text_poke as a cause of your crash. A bisection of sched-devel/latest seems appropriate.
Mathieu
> > Thanks. > > -- > Pekka Paalanen > http://www.iki.fi/pq/
-- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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