Date: Tue, 05 May 2009 16:23:30 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Jung-uk Kim <jkim@FreeBSD.org> Cc: Alan Amesbury <amesbury@umn.edu>, freebsd-acpi@freebsd.org, freebsd-stable@freebsd.org, Andriy Gapon <avg@icyb.net.ua> Subject: Re: Garbled output from kgdb? Message-ID: <4A00A042.20806@FreeBSD.org> In-Reply-To: <200905051609.38689.jkim@FreeBSD.org> References: <49F8B859.7060908@umn.edu> <4A006D38.50901@icyb.net.ua> <4A006E9A.7060806@icyb.net.ua> <200905051609.38689.jkim@FreeBSD.org>
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Jung-uk Kim wrote: > On Tuesday 05 May 2009 12:51 pm, Andriy Gapon wrote: >> BTW, this issue seems to be fixed in Jung-uk's acpi patches for >> newer acpica imports, but it is not fixed both in stable/7 and >> head. > > Yes, it was fixed in my patchsets long ago, which uses spin lock for > AcpiOsAcquireLock(). :-) I'm not sure all ACPI locks need to be spin locks, but any locks used by the idle code must be spin locks. Regardless, are you going to import a newer ACPI-CA and commit your patches soon? It sounds like several things are fixed in the outstanding patches by now including both this and the problem with the Alias() operator. > Jung-uk Kim > >> on 05/05/2009 19:45 Andriy Gapon said the following: >>> on 01/05/2009 22:01 John Baldwin said the following: >>>> The trace actually ends here. There is nothing super bad here >>>> but there is a big problem actually in that the idle threads >>>> cannot block on a lock, so it is a problem for the ACPI code to >>>> be acquiring a mutex here. Perhaps the locks protecting the >>>> idle registers need to use spin locks instead. The problem with >>>> blocking in the idle thread is that the scheduler assumes (even >>>> requires) that the idle thread is _always_ runnable. >>> Very interesting! So it seems that we are not having more of such >>> crashes by a pure luck (low probability)? >>> >>> Looking at the method's signature: >>> ACPI_NATIVE_UINT AcpiOsAcquireLock (ACPI_SPINLOCK Handle) >>> I think that the name of the parameter type is a big hint. >>> >>> Further, looking into ACPICA reference document: >>>> Wait for and acquire a spin lock. May be called from interrupt >>>> handlers, GPE handlers, and Fixed event handlers. Single >>>> threaded OSL implementations should always return AE_OK for this >>>> interface. >>> P.S. the comment before AcpiOsAcquireLock function (in stable/7 >>> code) seems to be outdated/bogus too - first of all there is no >>> Flags parameter (it's actualy a return value "to be used when >>> lock is released") and, second, having ithreads is no excuse to >>> not care about type of blocking, and the term 'blocking' is used >>> incorrectly too: >>> /* >>> * The Flags parameter seems to state whether or not caller is an >>> ISR * (and thus can't block) but since we have ithreads, we don't >>> worry * about potentially blocking. >>> */ -- John Baldwin
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