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

- Assert that a process is not swapped out in runq functions and

The update patchs is at:


On Sun, 28 Jul 2002 21:51:57 +0900,
  Seigo Tanimura <[EMAIL PROTECTED]> 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.


To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-current" in the body of the message

Reply via email to