Date: Fri, 23 Jun 2000 14:07:47 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Bruce Evans <bde@zeta.org.au> Cc: Jason Evans <jasone@canonware.com>, Greg Lehey <grog@lemis.com>, Warner Losh <imp@village.org>, The Hermit Hacker <scrappy@hub.org>, freebsd-smp@FreeBSD.ORG Subject: Re: SP Patchset #1 up Message-ID: <200006232107.OAA11962@apollo.backplane.com> References: <Pine.BSF.4.21.0006240527220.686-100000@besplex.bde.org>
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:> ...
:> If a debugger trap were to occur on the current cpu at just point, it
:> would indeed lead to a lockup. You are absolutely correct. So maybe
:> the comment should read: don't create any break points in between the
:> setting of curproc and the fixup of SchedMutex!
:
:Also: don't trace into the context switching code. This is very inconvenient.
:I've often typed 'n' in the debugger and then #$&* when the system crashes
:because ddb traced into nonreentrant code. (This happened yesterday when
:I tried 'n' to get a count of the number of instructions taken by a vmware
:ioctl.)
We can make tracing through the context switch code work. Hmm. We have
two choices: either make the context switch code trace-safe (by actually
unlocking SchedMutex when changing curproc), or make the DDB trap
save/override and restore the SchedMutex state, which is what it
did before. Sorta.
-Matt
Matthew Dillon
<dillon@backplane.com>
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