Re: [uml-devel] Re: The current fix-kill patch

[Blaisorblade <blaisorblade_spam@yahoo.it>]

On Tuesday 23 November 2004 16:10, Bodo Stroesser wrote:
> Jeff Dike wrote:
> > Here's the latest fix-kill patch in my tree.  Please test and report...

> Have tested based on 2.6.9-bb3. I removed "rework-uml-hang-on-2.6.9-host",
> added BlaisorBlade's "uml-hang-on-2.6.9-host", and adapted iand added this
> new patch.
Btw, if you send another patch, send it relative to "uml-hang-on-2.6.9-host", 
or to it + fix-kill from Jeff, so I can easily spot the differences.

This is a general rule, also (with a bit of taste, i.e. applies between 
developers, not between users).

> The resulting UML kernel for me works fine on host 
> 2.6.7-skas3-v7 and 2.6.9-skas3-v7.
Not yet tested this Jeff Dike's one.

However, for me, on a 2.6.10-rc2 SKAS patched host (with the update I posted 
here and on my site to make SKAS compile), UML hangs on shutdown in SKAS 
mode.

Nobody else reported this with -bb3, so I suppose there is something new in 
2.6.10-rc2 (I didn't yet test this with 

Please let's start testing it ASAP, so that it's fixed before 2.6.10 release. 
However, I have at least to apply the Jeff's fix before.

> Next, I tested what happens if the "kill(pid, SIGKILL);" and
> "ptrace(PTRACE_CONT, pid);" are removed from os_kill_ptraced_process(), and
> it also worked fine.

> Since PTRACE_KILL wakes up the ptraced process unconditionally, IMHO
> "ptrace(PTRACE_CONT, pid);" has no effect here.
You reported PTRACE_KILL not to work in some Ptrace states. PTRACE_CONT is 
intended to fix this (even if PTRACE_KILL is not needed).

> And "kill(pid, SIGKILL);" 
> only is needed, if the ptraced process is not stopped on a
> ptrace-interception.
Well, PTRACE_CONT is to resume if from the ptrace-interception. Let's start by 
distinguishing bugs (i.e. reggressions in 2.6.9 behaviour vs. 2.6.8 and 
earlier one) from strange APIs. Gdb, or any ptracer, is IMHO never supposed 
to SIGKILL the process directly.

> Since os_kill_ptraced_process() is called only then, 
> when the ptraced process is known to be on a ptrace-stop, I would like to
> remove "kill(pid, SIGKILL);", too.
> os_kill_ptraced_process() is called each time, a process in TT exec()s.
> Thus avoiding unneeded calls is a little speedup.

-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade



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