Benjamin Herrenschmidt <benh@kernel=2Ecrashing=2Eorg> wrote on 10/29/20=
06
07:47:05 PM:

On Fri, 2006-10-27 at 12:22 -0400, Jeff Bailey wrote:

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Le vendredi 27 octobre 2006 =E0 07:56 +0200, Fabio Massimo Di Nitto=

 a

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=E9crit :

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Hi everybody,

i am in the process of bootstrapping the new toolchain for ubuntu=

 and
I am

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hitting a problem building glibc-2=2E5 on ppc=2E

This behaviour has been reproduced on 2=2E6=2E15/2=2E6=2E17 and 2=

=2E6=2E19-

rc2 (where the

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machine crashes) and with ppc32 and ppc64 kernels=2E
A hard reboot of the machine is required to get rid of the Zl

processes hanging

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around that keep spinning the CPU at 100%=2E

I did place sources here: http://people=2Eubuntu=2Ecom/~fabbione/=

benh/

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but i start to believe it is a kernel bug we are exploiting only =

now=2E

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Any hint or help for what to look for would be extremely apprecia=

ted=2E

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Heya Fabio, just an update, it looks like the tests that are zombie=

'ing

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are the nptl tst-robust[1-8] tests=2E  According to /proc/##/wchan,=

 the

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tasks are cheerfully spinning in do_exit=2E

So I've built that glibc with debian 2=2E6=2E16 kernel headers (since=

 Fabio

says the problem doesn't happen with glibc built with 2=2E6=2E19 head=

ers)

and have ran that with 2=2E6=2E19-rc3-git-du-jour=2E

The machine didn't crash, nor did I see any zombie with those
tst-robust[1-8], however, I did get as SIGBUS with tst-robustpi1=2E I=

've

tracked it down to being an alignment exception=2E It looks like glib=

c is

doing a lwarx on a non-aligned value, though I can't say precisely
what's up here=2E I don't know how I can get a backtrace when running=

those test-cases=2E=2E=2E the test harness seems to catch signals, I =

suppose

it could be modified to spit one out=2E

At this point, it would be useful to have somebody who knows glibc to=

tell us:

 - what are those tst-robust all about ? (what do they do "special" t=

hat

might trigger bad reactions with older kernels)
 - how can glibc ever do atomic operations on a non-aligned value ?

Ben=2E

The tst-robustpi# test are exercising the new PTHREAD_MUXTEX_ROBUST api=
,
with PTHREAD_PRIO_INHERIT attribute=2E

The fuxtex word seems to include the waiters TID, I don't know if the
kernel cares about this or not=2E


Steven J=2E Munroe
Linux on Power Toolchain Architect
IBM Corporation, Linux Technology Center=