Date: Tue, 30 Jul 2002 01:22:35 +0900 From: Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> To: current@FreeBSD.org Cc: Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> Subject: Re: A fix of recent bugs in swapping in/out a process Message-ID: <200207291622.g6TGMZpK037474@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp> In-Reply-To: <200207281252.g6SCpvSH064272@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp> References: <200207281252.g6SCpvSH064272@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp>
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A couple of updates: - Optimize wakeup() and its friends; if a thread waken up is being swapped in, we do not have to ask for the scheduler thread to do that. - Assert that a process is not swapped out in runq functions and swapout(). The update patchs is at: http://people.FreeBSD.org/~tanimura/patches/procswap_2.diff.gz On Sun, 28 Jul 2002 21:51:57 +0900, Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> said: Seigo> If you are having a trouble of a broken thread state (eg a thread with Seigo> TDS_RUNQ on no run queue) or a mysterious page fault on a kernel Seigo> memory (probably in mi_switch()), you may want to try my patch at: Seigo> http://people.FreeBSD.org/~tanimura/patches/procswap.diff.gz Seigo> In a nutshell, this patch fixes three bugs: Seigo> 1. a thread with TDS_RUNQ on no run queue. Seigo> This is due to wakeup() and wakeup_one() setting the state to a thread Seigo> to TDS_RUNQ even if the thread has been swapped out. As a thread Seigo> being or having been swapped out cannot be scheduled immediately, Seigo> introduce a new thread state TDS_SWAPPED to note that. Seigo> 2. a possible race condition for multiple threads to swap in a single Seigo> process. Seigo> Since faultin() may block (and likely to do so) without leaving any Seigo> flags for a process being swapped in, more than one threads can call Seigo> faultin() for the same process. Avoid this by adding a new process Seigo> state flag PS_SWAPPINGIN to a process being swapped in. Seigo> 3. a running thread being swapped out. Seigo> Swapout_procs() and swapout() do not check the states of the threads Seigo> in a process about to be swapped out. This causes the pcb and the Seigo> kernel stack of a running thread being unmapped, resulting in a Seigo> page fault in cpu_switch(). Do not swap out a process unless all of Seigo> its threads are either in a run queue or sleeping. Seigo> Eventually, it may become our option to swap out only threads that are Seigo> safe to do so. -- Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> <tanimura@FreeBSD.org> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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