Date: Thu, 26 Mar 2009 17:15:39 +0200 From: Andriy Gapon <avg@icyb.net.ua> To: John Baldwin <jhb@FreeBSD.org> Cc: freebsd-acpi@FreeBSD.org Subject: Re: kern/108581: [sysctl] sysctl: hw.acpi.cpu.cx_lowest: Invalid argument Message-ID: <49CB9C1B.4070308@icyb.net.ua> In-Reply-To: <20090326151035.51e4196e@gluon.draftnet> References: <200903200030.n2K0U3iG011009@freefall.freebsd.org> <20090325223914.4387eeae@gluon.draftnet> <49CB8C86.4020800@icyb.net.ua> <20090326142832.0dba187a@gluon.draftnet> <49CB9224.6010509@icyb.net.ua> <20090326144140.2203c0d8@gluon.draftnet> <49CB9973.3010306@icyb.net.ua> <20090326151035.51e4196e@gluon.draftnet>
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on 26/03/2009 17:10 Bruce Cran said the following: > On Thu, 26 Mar 2009 17:04:19 +0200 > Andriy Gapon <avg@icyb.net.ua> wrote: > >> on 26/03/2009 16:41 Bruce Cran said the following: > >>> I added lots of printfs to acpi_cpu.c and found that it's occuring >>> in acpi_cpu_startup; initializing it to 3 in that function (which I >>> wrongly assumed was the lowest Cx state supported in ACPI) fixed >>> the problem on my Athlon XP PC because the generic cx handling code >>> then lowered cpu_cx_count to 1 based on the fact that >>> sc->cpu_cx_count was also 1. >>> >> Ok, yes, the real issue is in acpi_cpu_generic_cx_probe, namely in >> early exits from it. So, sc->cpu_cx_count is always set to at least >> 1, but if we exit via one of the returns before the end of function, >> then global cpu_cx_count is never updated. >> > > Exactly: > > acpi: acpi_cpu_startup: initializing cpu_cx_count to 0 > acpi_cpu_generic_cx_probe > if sc->cpu_p_blk_len < 5 [sc->cpu_p_blk_len = 0] > acpi: acpi_cpu_startup: cpu 0,cpu_cx_count = 0,sc->cpu_cx_count = 1 > > So we're hitting an early exit in acpi_cpu_generic_cx_probe. > John, what would be a better fix - initialize the global variable to 1 or use goto in acpi_cpu_generic_cx_probe? I think the latter is more consistent and obvious, the former is simpler and safer, though. -- Andriy Gapon
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