Re: [uml-devel] handle_trap - failed to wait at end of syscall

[BlaisorBlade <blaisorblade_spam@yahoo.it>]

On Monday 13 September 2004 17:39, Joe Marzot wrote:
> remeber this one?...the latest take on this is that because we launch
> UMLs from a perl script (using fork/exec) when the perl script exits a
> SIGHUP is transmitted to the UML proc which sometimes interrupts a
> waitpid()...if that interruption occurs during the nullification of a
> syscall (now that I know what that means:) then you get a kernel panic
> like below.

> I made a small fix that seems to be working for me and looks like what's
> going on in CATCH_EINTR

> can't do this globally in CATCH_EINTR since some waitpids don't check
> status...maybe they should...maybe there is a more correct way to do
> this altogether...
I'm going to merge something like this. Also, sorry - it's about a month that 
I should do this and keep forgetting to work on other stuff.

However, it is not possible nor desirable to do this in CATCH_EINTR - retry if 
errno == EINTR is a general rule valid in every Unix program ever, while this 
is very specific to this call.

> do {
>    CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
> } while (WIFSTOPPED(status) && (STOPSIG(status) == SIGHUP))

I'll turn that to STOPSIG(status) != SIGTRAP. I'm getting the same problem 
with SIGSEGV instead (IIRC).

However, maybe that must be != SIGTRAP and != <other signal>. I don't think 
so, but I must check to be sure. Jeff, what do you think?

Also, we don't make a distinction between real SIGTRAP and syscall stop.

Jeff, would you agree to using PTRACE_O_SYSGOOD?
See arch/i386/kernel/ptrace.c:do_syscall_trace for an explaination of this 
func.

-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729


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