From owner-freebsd-smp Thu Oct 5 14:46:56 2000 Delivered-To: freebsd-smp@freebsd.org Received: from pike.osd.bsdi.com (pike.osd.bsdi.com [204.216.28.222]) by hub.freebsd.org (Postfix) with ESMTP id 5BFD737B503; Thu, 5 Oct 2000 14:46:47 -0700 (PDT) Received: from laptop.baldwin.cx (john@dhcp248.osd.bsdi.com [204.216.28.248]) by pike.osd.bsdi.com (8.11.0/8.9.3) with ESMTP id e95Lkai16181; Thu, 5 Oct 2000 14:46:36 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Message-ID: X-Mailer: XFMail 1.4.0 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: Date: Thu, 05 Oct 2000 14:46:49 -0700 (PDT) From: John Baldwin To: John Baldwin Subject: RE: Problems with kthread_exit() and SMPng Cc: freebsd-current@FreeBSD.org, freebsd-smp@FreeBSD.org, Boris Popov Sender: owner-freebsd-smp@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Ugh, my mail client ate my reply, lemme try again. > On 05-Oct-00 Boris Popov wrote: >> Hello, >> >> Currently I'm trying to make KLD which uses kernel threads >> unloadable under recent -current. The prototype of functions looks like >> this: >> >> void >> my_thread(void*arg) >> { >> while(wearewanted) { >> do_something(); >> tsleep(); >> } >> exited = 1; >> kthread_exit(0); >> } You need Giant before calling kthread_exit(). >> void >> my_unload() >> { >> wearewanted = 0; >> while (!exited) >> tsleep(1sec); >> } >> >> my_unload() function called from the module unload event which >> issued from the kldunload() syscall. >> >> Unfortunately, kernel panics in the mtx_exit_hard() function. >> After some examination I've found that two fields in the Giant mutex >> structure set to unexpected values: It should have died much earlier if you had INVARIANTS turned on. :( It looks like you are releasing a mutex you probably do not own because cpu_exit() (called by exit1() -> exit() -> kthread_exit()) releases Giant as one of its final tasks. >> ---- >> empty mtx_blocked for mutex Giant >> mtx_contested not in any list for mutex Giant >> ---- >> >> These messages printed by added diagnostics code. With this patch >> (see attachment) it is possible to load and unload KLD without any >> problems on UP machine except that the above messages printed. However, >> I'm don't know if they are correct. (btw, 4.1 doesn't have this problem). This patch is bogus I'm afraid. A contested mutex should always have a process waiting to grab it when it is released. -- John Baldwin -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.baldwin.cx/~john/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message