From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4C1BC3BA.3020603@domain.hid> Date: Fri, 18 Jun 2010 21:06:34 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4C095876.3060605@domain.hid> <4C099329.6000303@domain.hid> <4C0A49C4.8000509@domain.hid> <4C0A9AB9.7030602@domain.hid> <4C0A9C2A.1030002@domain.hid> <4C0AA224.6060409@domain.hid> <4C0AA2F0.6050201@domain.hid> <4C0AA3EC.7040106@domain.hid> <4C0AA548.6070409@domain.hid> <4C0AB7BA.7000100@domain.hid> <4C0B9846.7050203@domain.hid> <4C1BC224.5040505@domain.hid> In-Reply-To: <4C1BC224.5040505@domain.hid> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-core] [Xenomai-git] Jan Kiszka : native: Rework handling of pthread carrier thread List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: xenomai-core Jan Kiszka wrote: > Gilles Chanteperdrix wrote: >> However, I do not have a strong opinion on this, it is just an open >> question. More generally, I would like us to discuss once and for all >> about the semantic of the various calls and their effect on the RT_TASK >> duration, instead of changing this semantic every release and risk >> breaking non-broken applications (I mean, the one which do not segfault). > > To pick up this issue again (in order to get my queue flushed): > > We basically have to decide about the question what rt_task_delete > invalidates and what impact this shall have on rt_task_join. It is > already documented that rt_task_delete invalidates (and releases) the > kernel-side resources of a RT_TASK. The question is what shall happen to > the not explicitly mentioned user-side resources (ie. the pthread - > where available). > > Option 1 is to decouple both and keep the user side of a joinable > RT_TASK alive until it is explicitly joined. Option 2 could be to > declare both parts invalid on rt_task_delete. Based on this decision, > the finalization logic of rt_task_delete and rt_task_join then needs to > be adjusted to deliver the right behavior, including proper error codes > instead of sporadic SEGV. Relying on the contents of the RT_TASK structure to know the state of a task is bound to fail: the RT_TASK structure may be copied around, so changing the contents of the RT_TASK structure in rt_task_delete, to use that information later will only work if the same RT_TASK structure is used later. This is fragile. > > Do we expect applications to rely on this joinability after > rt_task_delete? If yes, we should make it official, document the > descriptor split and the fact that the descriptor cannot be looked up > anymore after deletion but has to be saved beforehand. > > Independently, we need to clarify that cross-process join is not > supported. Trying to do this ATM will result in a SEGV (something I > missed so far). This is a regression. At some point in the past, a NULL pthread_t opaque pointer was used to mean that the thread was living in a different process, and rt_task_delete would skip the pthread_cancel. -- Gilles.