From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4B8D1AD8.5070507@domain.hid> Date: Tue, 02 Mar 2010 15:04:08 +0100 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4B8D0359.4070504@domain.hid> <4B8D0466.7040403@domain.hid> <4B8D0542.1020904@domain.hid> <4B8D05B3.1020202@domain.hid> <4B8D07D7.4040108@domain.hid> <4B8D091A.7070908@domain.hid> <4B8D0BA5.505@domain.hid> <4B8D0CE7.6020101@domain.hid> <4B8D11A6.9070400@domain.hid> <4B8D12FA.6040807@domain.hid> <4B8D13E9.3010109@domain.hid> <4B8D14BE.8050503@domain.hid> <4B8D164D.7000906@domain.hid> <4B8D16B9.8090609@domain.hid> <4B8D1A07.4050804@domain.hid> In-Reply-To: <4B8D1A07.4050804@domain.hid> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-core] [Xenomai-git] Jan Kiszka : Native: Fix return code of in-kernel rt_cond_wait[_until] 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: >> Jan Kiszka wrote: >>> Gilles Chanteperdrix wrote: >>>> Jan Kiszka wrote: >>>>> Gilles Chanteperdrix wrote: >>>>>> Jan Kiszka wrote: >>>>>>> Gilles Chanteperdrix wrote: >>>>>>>> Ok for returning -EINTR, it is documented. Kernel-space is not so >>>>>>>> different from user-space, rt_task_unblock could wake-up a kernel-space >>>>>>>> task blocked in a call to rt_cond_wait. >>>>>>>> >>>>>>>> However, if the epilogue returns an error, we must return it. >>>>>>>> >>>>>>> OK for this. Pushed an update, but I also modified it further to avoid >>>>>>> returning without the mutex lock unless that one is also failing. Maybe >>>>>>> in-kernel POSIX requires the same fix, will check. >>>>>> Still not OK. You should reacquire the mutex only if the error is 0, >>>>>> -ETIMEDOUT or -EINTR. With any other error, we do not know if we can >>>>>> call the epilogue safely. >>>>> We _must_ reacquire the mutex - but, granted, we actually have to take >>>>> care of invalid cond objects. Lot's of bugs... >>>> No. If the error is another error than 0, -ETIMEDOUT, or -EINTR, it >>>> means that the error was detected prior to freeing the mutex. So, we do >>>> not have to re-acquire the mutex. Quoting POSIX: >>>> >>>> "Except in the case of [ETIMEDOUT], all these error checks shall act as >>>> if they were performed immediately at the beginning of processing for >>>> the function and shall cause an error return, in effect, prior to >>>> modifying the state of the mutex specified by mutex or the condition >>>> variable specified by cond." >>>> >>>> POSIX does not talk about -EINTR, because it states that in this case, >>>> we should return 0 to the application. >>> OK, but EIDRM was missing in your list. Will adjust both patches. >> No, EIDRM is part of the "other errors than ETIMEDOUT and 0" >> > > I interpret the spec fairly differently here: It states that we have to > leave the mutex state behind *as if* the error was already detected on > entry - thus we are expected to restore its state. No. We must return prior to modifying its state. Not change its state then restore it. There is no EIDRM anyway, I return 0, and the user gets EINVAL when calling pthread_cond_wait again. -- Gilles.