[PATCH] RFC: do not detach when we think tracee is going to die

[Dmitry V. Levin]

On Mon, Aug 15, 2011 at 12:01:56PM +0200, Denys Vlasenko wrote:
> On Tue, 2011-08-02 at 01:45 +0400, Dmitry V. Levin wrote:
> > On Sat, Jun 25, 2011 at 11:34:23AM +0200, Denys Vlasenko wrote:
[...]
> > > I need to look in the past to figure out why we even do it.
> > > First guess is that it's a workaround for old kernel bugs.
> > 
> > How old those buggy kernels might be?
> 
> The internal_exit function, whose reason for existence is to 
> support "detach on exit" behavior, is from 1995.
> 
> I tried to test whether this is still needed on kernel 2.4.20,
> but this kernel oopses (somewhere in ptrace_check_attach).

I tried to test current strace with linux-2.4.32-ow1 from
ftp://ftp.openwall.com/pub/Owl/2.0-release/iso/Owl-2.0-release-i386.iso.gz
where PTRACE_SETOPTIONS are certainly not supported, and found out that
test_ptrace_setoptions_followfork() fails to wait for all child processes
it generates, resulting to an unexpected wait failure later in
test_ptrace_setoptions_for_all().

I've just pushed a fix to
http://strace.git.sourceforge.net/git/gitweb.cgi?p=strace/strace;a=commitdiff;h=ldv/PTRACE_SETOPTIONS-tests
please have a look.

With the fix, at least simple strace -f test works on linux-2.4.32.
There are no kernel oopses there, but ./strace -f ./test/childthread
outputs something different from expected.

> Do you think it would be better if we recommend users of
> 2.4 kernels to simply stick with older strace versions?

Do we have an alternative choice now?


-- 
ldv
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