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Date: Thu, 5 Oct 2023 15:39:26 +0200
From: Szabolcs Nagy <nsz@port70.net>
To: Carl Chave <online@chave.us>
Cc: Rich Felker <dalias@libc.org>, musl@lists.openwall.com
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Subject: Re: [musl] Hung processes with althttpd web server

* Carl Chave <online@chave.us> [2023-10-04 22:43:16 -0400]:
> > 1. What Alpine/musl version are you using? If it's older, it might be
> >    something that would be different in current versions.
> 
> Alpine 3.18.3 with musl package musl-1.2.4-r1 x86_64
> 
> > 2. Can you attach gdb to the hung process and identify what lock
> >    object it's waiting on?
> 
> I don't really know what I'm doing with gdb. This is probably not helpful:
> (gdb) bt
> #0  0x00007f5fb449c0dd in ?? () from /lib/ld-musl-x86_64.so.1
> #1  0x0000000000000002 in ?? ()
> #2  0x0000000000000000 in ?? ()

you might want to

apk add musl-dbg

the bt should be more useful then.

in this case you can also look at

(gdb) disas $rip-40,+80
(gdb) info reg

since the address is the first arg to a futex syscall (rdi).
then you can try to dig around to see where rdi points to

(gdb) x/4wx $rdi-4
(gdb) info sym $rdi

etc