On Sun, Jun 04, 2017 at 11:38:14AM +1000, Anton Blanchard wrote: > On Sat, 3 Jun 2017 19:42:14 -0300 > Breno Leitao <lei...@debian.org> wrote: > > > Hi Anton, > > > > On Sat, Jun 03, 2017 at 08:04:11AM +1000, Anton Blanchard wrote: > > > Hi Breno, > > > > > > > Currently tsk->thread->load_vec and load_fp are not initialized > > > > during a task creation, which set garbage to these variables > > > > (non-zero value). > > > > > > Nice catch! It seems like we should zero load_tm too though? > > > > Yes, it seems we need to zero load_tm also, since it does not seem to > > be zeroed anywhere else. > > > > But I did some tests, and load_tm is always zero after start_thread() > > is being called. > > > > In fact, start_thread() is being called and pt_regs->load_tm is > > already zero since the function start. > > > > I also wrote a SystemTap script[1] to investigate it better, and I've > > never seen a single load_tm != 0 in a my machine. I tested on both > > POWER8 bare metal and KVM guests. (load_vec and load_fp happened to > > have garbage all the time) > > > > Any idea if this is just occasional event, or, if there is someone > > zeroing it in an obscure code? > > Quite likely no one uses TM :) Try:
In fact, I had tested with TM[1] and haven't seen any issue, but I was not calling a nested application (through execve() syscall). Somehow if I call "$ ./tm_application ; /bin/true", I do not see a non-zero load_tm in the new task->thread. On the other side, I see the corruption with your test case, mainly if I sleep after 'tbegin.' and before execlp(), giving a chance to have load_tm incremented, and this value is being inherited in the new task->thread. This is obviously wrong, I will send a patch to have it fixed. Thanks for the guidance! [1] https://github.com/leitao/htm_torture