From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <48BD3209.7080303@domain.hid> Date: Tue, 02 Sep 2008 14:31:05 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <48BBA9E6.5070400@domain.hid> <48BBAB67.90707@domain.hid> <48BBD8E4.6010702@domain.hid> <48BBF299.7060205@domain.hid> <48BBF59A.6060208@domain.hid> <48BBF627.9040907@domain.hid> In-Reply-To: <48BBF627.9040907@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-core] [PATCH 2/9] Switch to handle-based fast mutex owners List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" 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: >>>>> To improve robustness of the fast mutex implementation in POSIX (and >>>>> later on in native), it is better to track the mutex owner by handle >>>>> instead of kernel object pointer. Therefore, this patch changes >>>>> __xn_sys_current (xeno_set_current) so that it returns >>>>> xnthread_handle(current_thread). It furthermore converts the POSIX mutex >>>>> implementation to pick up and store the lock owner as handle in the >>>>> kernel/user-shared mutex. Finally it ensures that all skins (except for >>>>> RTDM which must not mess around with foreign skins anyway) add their >>>>> threads to the registry so that at least anonymous handles are >>>>> available. >>>>> >>>>> As the value stored in the mutex variable is now an integer, we can >>>>> switch over to xnarch_atomic_t, removing all atomic_intptr users. >>>> The current implementation allows RTDM threads to use POSIX skin >>>> mutexes. I do not see why this should change. >>> Such mixup might technically be possible now. But there is neither a >>> need nor does it make the resulting driver more portable. I don't want >>> to introduce needless thread registration to RTDM just to cover >>> theoretical use cases that should not exist in the first place. >>> >>> Nevertheless, some sanity check will have to be added to the >>> to-be-written generic xnsynch support to catch missing thread handles. >>> That make sense for checking future skin implementation as well. >> That is overhead in the hot path, whereas adding the thread registration >> takes place in a non hot path. > > It will be a debug check. Ok. But the other points remain. -- Gilles.