kse_release and kse_wakeup problem (fwd)

[John Baldwin]

On Monday 26 April 2004 01:38 pm, Daniel Eischen wrote:
> On Mon, 26 Apr 2004, Daniel Eischen wrote:
> > On Mon, 26 Apr 2004, David Xu wrote:
> > > John Baldwin wrote:
> > > > I.e. do the upcall check in sleepq_catch_signals() right where you
> > > > already do thread_suspend_check(1).  The only reason you have to do
> > > > this, btw, is because the kse_release() code is trying to mess with
> > > > thread state internals using sleepq_abort(), etc.  The other
> > > > in-kernel code that does that (signals) already does the check in
> > > > sleepq_catch_signals() and has done the same type of check in
> > > > msleep()/tsleep() for quite a while.
> > > >
> > > > If the kse_release() stuff was just using sleep/wakeup() rather than
> > > > trying to manually abort sleeps it wouldn't have to be so intimate
> > > > with the sleep interface.
> > > >
> > > > Note that thr's thr_wakeup() and thr_sleep() manage to simulate
> > > > synchronization w/o having to abort sleeps, but it is probably also
> > > > easier to do that than for the M:N case.
> > >
> > > I think libthr will encounters same problem as libpthread with new
> > > sleep queue code, because mtx is released too early in msleep before
> > > thread markes itself as ON_SLEEPQ, thr_suspend and thr_wakeup have same
> > > race window as kse_release and kse_wakeup. Any code wants to put
> > > synchronous bit in td_flags like these codes will be broken.
> >
> > I'm experimenting with adding an wakeup_thread() to kern_thread.c
> > (to complement wakeup() and wakeup_one()).  If we shouldn't be
> > using sleepq's directly, the thread code either needs to
> >
> >   a) queue msleep()'ing upcalls/threads itself having them
> >      all block on on their own unique wchan's; or
> >
> >   b) use a wakeup_thread() that wakes up a specific thread.
>
> Sorry, patch for b) is at:
>
> 	http://people.freebsd.org/~deischen/sys.diffs

Erm, does sleepq_signal_thread() do anything different than sleepq_remove() 
(removes a thread from a specified wait channel if and only if the thread is 
sleeping on that wait channel)?

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org