load lib

[Gianni Mariani]

Adv wrote:

> Hi,
> I get aborted when dlclose() on a gnu/linux box and my code runs as a
> multithreaded server, so, is dlclose()/dl...() thread-safe? if not, how
> about elf's auto load? the loaded lib is/isn't thread safe will not be issue
> here?

dlclose() will unmap the library from the process.

Hence, if you are still needing it (perhaps a return address on the
stack or a virtual destructor or whatever) it will SEGV.

dlopen/dlclose is probably not thread safe (since it needs to run before
a thread library is available) but that's an easy fix to wrap them in
a mutex.

[DL]

There are two things, first, I have used some mutexes and I don't want to
make things more complicated for me :), second, auto loading will not have
such an issue, will it?
?

How about keep the "handle" (via dlopen()) visible globally, and call
ldsym() without a mutex involoved in each thread?




"Gianni Mariani" <gi2nospam@mariani.ws> wrote in message
news:bf2unu$35b@dispatch.concentric.net...

> Adv wrote:

> > Hi,
> > I get aborted when dlclose() on a gnu/linux box and my code runs as a
> > multithreaded server, so, is dlclose()/dl...() thread-safe? if not, how
> > about elf's auto load? the loaded lib is/isn't thread safe will not be

issue

> > here?

>
> dlclose() will unmap the library from the process.
>
> Hence, if you are still needing it (perhaps a return address on the
> stack or a virtual destructor or whatever) it will SEGV.
>
> dlopen/dlclose is probably not thread safe (since it needs to run before
> a thread library is available) but that's an easy fix to wrap them in
> a mutex.
>
>

[Valentin Nechayev]

>>> Gianni Mariani wrote:

GM> dlopen/dlclose is probably not thread safe (since it needs to run before
GM> a thread library is available) but that's an easy fix to wrap them in
GM> a mutex.

1. Thread library can be loaded not only by dlopen(), but by runtime
loader (rtld), such as (/lib|/usr/lib|/usr/libexec)/(ld.so|ld-elf.so|...)
2. There are issues except simple serialization of accessing dl*() internal
structures; see recent history of FreeBSD rtld.
3. Even if function is made thread-safe with explicit serialization, it
can be used without threading library; again, see FreeBSD implementation
for malloc().


-netch-