Date: Tue, 5 May 2009 16:09:35 -0400 From: Jung-uk Kim <jkim@FreeBSD.org> To: Andriy Gapon <avg@icyb.net.ua> Cc: Alan Amesbury <amesbury@umn.edu>, freebsd-acpi@freebsd.org, freebsd-stable@freebsd.org, John Baldwin <jhb@freebsd.org> Subject: Re: Garbled output from kgdb? Message-ID: <200905051609.38689.jkim@FreeBSD.org> In-Reply-To: <4A006E9A.7060806@icyb.net.ua> References: <49F8B859.7060908@umn.edu> <4A006D38.50901@icyb.net.ua> <4A006E9A.7060806@icyb.net.ua>
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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(). :-) 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 code) seems to be outdated/bogus too - first of all there is no 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. > > */
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