> -----Original Message----- > From: Jan Kiszka <jan.kis...@siemens.com> > Sent: Dienstag, 21. Jänner 2020 18:46 > To: Lange Norbert <norbert.la...@andritz.com>; Xenomai > (xenomai@xenomai.org) <xenomai@xenomai.org> > Subject: Re: Cobalt deadlock for no apparent reason > > NON-ANDRITZ SOURCE: BE CAUTIOUS WITH CONTENT, LINKS OR > ATTACHMENTS. > > > On 20.01.20 19:03, Lange Norbert via Xenomai wrote: > > Hello, > > > > I got a deadlock while running through gdbserver, this is an > > implementation of a synchronized queue, Fup side waits via condition > variable, main wants to push data, but main fails to acquire the mutex. > > The mutex is an errorchecking type, without priority inheritance, and not > used elsewhere. > > > > > > The task are as following: > > > > CPU PID CLASS TYPE PRI TIMEOUT STAT NAME > > 1 1686 rt cobalt 4 - Wt main > > 3 1690 rt cobalt 2 - Wt fup.medium > > > > main is stuck in this function > > > > int mutex_lock(struct mutex_data *pData) { > > pthread_t threadId = pthread_self(); > > // assert(pthread_equal(threadId, pData->m_LockId) == 0); > > -> int r = pthread_mutex_lock(&pData->m_Mutex); > > assert(r == 0); > > pData->m_LockId = threadId; > > return r; > > } > > > > In libcobalt: > > do > > ret = XENOMAI_SYSCALL1(sc_cobalt_mutex_lock, _mutex); > > while (ret == -EINTR); > > > > fup.medium is stuck in: > > > > int conditionvar_wait(struct conditionvar_data *pData, struct > > mutex_data *pMutex) { > > pthread_t sid = pthread_self(); > > assert(pthread_equal(sid, pMutex->m_LockId) != 0); > > pMutex->m_LockId = 0; > > -> int r = pthread_cond_wait(&pData->m_CondVar, &pMutex- > >m_Mutex); > > assert(r == 0); > > pMutex->m_LockId = sid; > > return r; > > } > > > > In libcobalt: > > while (err == -EINTR) > > err = XENOMAI_SYSCALL2(sc_cobalt_cond_wait_epilogue, _cnd, _mx); > > > > This is likely tricky to debug by just looking at things. Can you factor out a > reproducer?
Well, the "no apparent reason" is key here, it's not easily reproducible either. Might help if you tell me how I could end up in this situation, AFAIK the pthread_cond_wait function got an interrupt, when can this occur for example. It seems limited to running under a debugger (or just happens a lot less without), and when the process dlopen's libraries this pauses the process for example. At that time the fup.medium is supposed to stick in pthread_cond_wait (means the dlopens might cause spurious wakeups) and notified after everything is ready to run. So, if you have any idea how I could narrow it down, I migh be able to build a reproducer. Right now I am going to use a timed mutex to atleast detect the issue. Norbert ________________________________ This message and any attachments are solely for the use of the intended recipients. They may contain privileged and/or confidential information or other information protected from disclosure. If you are not an intended recipient, you are hereby notified that you received this email in error and that any review, dissemination, distribution or copying of this email and any attachment is strictly prohibited. If you have received this email in error, please contact the sender and delete the message and any attachment from your system. ANDRITZ HYDRO GmbH Rechtsform/ Legal form: Gesellschaft mit beschränkter Haftung / Corporation Firmensitz/ Registered seat: Wien Firmenbuchgericht/ Court of registry: Handelsgericht Wien Firmenbuchnummer/ Company registration: FN 61833 g DVR: 0605077 UID-Nr.: ATU14756806 Thank You ________________________________