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Date:      Mon, 2 Jun 1997 15:29:10 +0930 (CST)
From:      Michael Smith <msmith@atrad.adelaide.edu.au>
To:        dg@root.com
Cc:        msmith@atrad.adelaide.edu.au, hackers@FreeBSD.ORG
Subject:   Re: weird scheduler crash (2.2)
Message-ID:  <199706020559.PAA18982@genesis.atrad.adelaide.edu.au>
In-Reply-To: <199706020546.WAA29447@implode.root.com> from David Greenman at "Jun 1, 97 10:46:00 pm"

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David Greenman stands accused of saying:
> >calltrap() at calltrap+0x15
> >--- trap 0xc, eip = 0xf0117408, esp = 0xefbffe84, ebp = 0xefbffe88 ---
> >_unsleep(f0d0cc00) at _unsleep+0x48
> >_selwakeup(f0214348) at _selwakeup+0x76
> >_mdsiointr(0,10,f020f9dc,118,ffffffff) at _mdsiointr+0x184
> >_Xfastintr10(f020f9dc,118,f011cb84,b,f01f5748) at _Xfastintr10+0x17
> >_select(f0d0cc00,efbfff94,efbfff84) at _select+0x2e2
> >_syscall(27,27,4,4,efbf77d4) at _syscall+0x127
> >_Xsyscall() at _Xsyscall+0x35
> >--- syscall 0x5d, eip = 0x7c945, esp = 0xefbf7568, ebp = efbf77d4 ---
> >
> >have.  It looks like the driver (mdsio) took an interrupt during a
> >select syscall which in turn resulted in the driver trying to wake the
> >selecting process up again.
> 
>    What is mdsio? It looks like it is configured as a "fast" interrupt
> handler, but is breaking the rules by calling the wakeup code.

Ah, this is something I didn't know about.  It's "just" an ISA driver.

How do I determine whether an interrupt handler is configured "fast" or 
"slow"?  Where are the rules for "fast" and "slow" handlers described?

The mdsio driver is another 8250-family UART driver that talks 9-bit
multidrop mode.

> -DG

-- 
]] Mike Smith, Software Engineer        msmith@gsoft.com.au             [[
]] Genesis Software                     genesis@gsoft.com.au            [[
]] High-speed data acquisition and      (GSM mobile)     0411-222-496   [[
]] realtime instrument control.         (ph)          +61-8-8267-3493   [[
]] Unix hardware collector.             "Where are your PEZ?" The Tick  [[



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