On Tue, Sep 02, 2008 at 09:38:20AM +0800, David Xu wrote: > Kostik Belousov wrote: > >On Mon, Sep 01, 2008 at 03:17:46PM +0300, Andriy Gapon wrote: > >>on 01/09/2008 14:12 Kostik Belousov said the following: > >>>On Mon, Sep 01, 2008 at 01:53:23PM +0300, Andriy Gapon wrote: > >... > >>>>>>>The following silly patch fixes the problem Andriy encountered: > >>>>>>I can confirm - this fixed the issue for me. > >>>>>>David, thanks! > >>>>>Does libc_r still work with patch applied ? > >>>>In what sense? > >>>>The test program that I posted seems to hang in both cases (patched and > >>>>unpatched rtld). > >>>The David' patch changes the code used to support libc_r operations. > >>>Even on CURRENT, if you run 4.x-compiled binary with the support of > >>>compat-4x libraries, this code from /libexec/ld-elf.so.1 (installed > >>>by CURRENT buildworld) provides locking for rtld. > >>I understand, but I am not sure what exactly needs to be tested. > >>"Still works" is too broad in this context. > > > >I am not sure too. As I said, this one of the reason I prefered to not > >touch that code. > > It should not affect other code outside the rtld. In fact, this patch > fixes the maintenance of synchronization between locks and thread_flag. > In current code, if you acquire a rwlock, and then acquire second > rwlock, the first one will work, but acquiring second lock will fail > and thread_flag is out of sync, this results bit flag leaking in > thread_flag, and later a _rtld_thread_init() call will transfer the > unlocked rwlock state to libthr as locked state, also the existing > code does not distinguish reader lock and writer lock, it blindly > transfer lock state as write-lock, fortunately, in correct case, > it should not be called with any lock held, so the transferring > does not occur. Yes, I understand this. And, this code is used when threading implementation is provided by libc_r, see above. I have no objection against that patch, but I think that it shall be verified whether compat-4x threaded programs work correctly with the change. > Another question is why should dl_iterate_phdr() use exclusive lock ? > doesn't this cause all C++ exception to be executed in serialization > manner ? It is required by C++ runtime. See the commit log for r178807.
Attachment:
pgp7Xqqq9PGXR.pgp
Description: PGP signature