From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Remy Bohmer" Subject: Re: [BUG on PREEMPT_RT, 2.6.23.1-rt5] in rt-mutex code and signals Date: Sat, 17 Nov 2007 18:09:15 +0100 Message-ID: <3efb10970711170909n3acca605j70525e36faf8da7f@mail.gmail.com> References: <3efb10970711160751l279fe99dl9f3a130a4373a449@mail.gmail.com> <3efb10970711161502m6216bf5rc19a34184b4f3a2b@mail.gmail.com> <3efb10970711170344n670d8b69w6679d494922c5bb@mail.gmail.com> <1195316550.25393.21.camel@imap.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Steven Rostedt" , "Ingo Molnar" , "Thomas Gleixner" , RT , linux-kernel To: "Daniel Walker" Return-path: Received: from py-out-1112.google.com ([64.233.166.181]:20223 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751332AbXKQRJQ (ORCPT ); Sat, 17 Nov 2007 12:09:16 -0500 Received: by py-out-1112.google.com with SMTP id u77so4842301pyb for ; Sat, 17 Nov 2007 09:09:15 -0800 (PST) In-Reply-To: <1195316550.25393.21.camel@imap.mvista.com> Content-Disposition: inline Sender: linux-rt-users-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org Hello Daniel, Thanks for looking into it also. Steven already made clear to me that the 'struct semaphore' type on the RT-kernel should not be used as a counting-semaphore, but as some sort of legacy-mutex... (The confusion that this will cause is clear by now...) I still do not understand the problems I had with the interruptible-waits on a real rt-mutex, but I have to figure that out again on Monday. Maybe one confusion let to another... (Note, A completion will not work for me, because they are not designed for reuse across several threads. The read/write runs in user context and as such it can be called by different threads, which would require a init of a completion before waiting on it, but that would be racy, I could miss the awake by the init) > So I converted your code to use a compat_semaphore, and no oops > happens.. Which makes sense because compat_semaphores are designed to > work the way your using them. Actually, IMO, compat_semaphores behave like semaphores should behave, and thus the same as they behave on a non-RT kernel, and at the locations where the semaphores are now misused as mutexes on RT, we should replace them by differently-named-mutex-type-semaphores, or better: real-RT-mutexes.. IMO this wrong usage of semaphores is solved by modifying the code that actually made proper use of the semaphores, and I think that if the naming matches the mainline kernel, we only need to patch the files that really need to be patched during the integration in mainline of the RT-patch. Kind Regards, Remy Bohmer