Date: Tue, 27 Apr 2004 09:47:08 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Daniel Eischen <eischen@vigrid.com> Cc: David Xu <davidxu@FreeBSD.org> Subject: Re: kse_release and kse_wakeup problem (fwd) Message-ID: <200404270947.08523.jhb@FreeBSD.org> In-Reply-To: <Pine.GSO.4.10.10404261329260.1789-100000@pcnet5.pcnet.com> References: <Pine.GSO.4.10.10404261329260.1789-100000@pcnet5.pcnet.com>
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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@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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