Date: Thu, 26 May 2011 19:30:57 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: mdf@FreeBSD.org Cc: Attilio Rao <attilio@FreeBSD.org>, src-committers@FreeBSD.org, Pawel Jakub Dawidek <pjd@FreeBSD.org>, svn-src-user@FreeBSD.org Subject: Re: svn commit: r222060 - in user/avg/xcpu/sys: kern sys Message-ID: <4DDE8041.7060903@FreeBSD.org> In-Reply-To: <BANLkTi=X_zddoAbZfXqtuzLut16zCVi%2BTg@mail.gmail.com> References: <201105181508.p4IF8UoS096841@svn.freebsd.org> <20110518182441.GB2273@garage.freebsd.pl> <4DD4243C.4070301@FreeBSD.org> <BANLkTikAnB-3XbvDwGHgyqyJquH9BhqzOQ@mail.gmail.com> <4DDD13F9.5040800@FreeBSD.org> <4DDE7555.7090500@FreeBSD.org> <BANLkTim_zEDPANqZTpyYdOKqDaPEc8EhVg@mail.gmail.com> <4DDE7A36.2050104@FreeBSD.org> <BANLkTi=X_zddoAbZfXqtuzLut16zCVi%2BTg@mail.gmail.com>
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on 26/05/2011 19:18 mdf@FreeBSD.org said the following: > On Thu, May 26, 2011 at 9:05 AM, Andriy Gapon <avg@freebsd.org> wrote: >> on 26/05/2011 18:46 mdf@FreeBSD.org said the following: >>> A per-thread flag is needed as long as other CPUs can be running or >>> even just the scheduler on the remaining CPU. So I would thing that >>> flag needs to be checked until the system has been massaged to the >>> state you describe above. >> >> I am not sure that I understand your reasoning if you mean that the flag needs to >> be checked in TD_IS_INPANIC. That is, right now there is no TD_IS_INPANIC and >> things work after panic to a certain degree. I do not intend to improve that >> degree and just want to keep an option to revert to the current state of matters. >> When TD_IS_INPANIC is introduced and stop_cpus_on_panic==1, then there will be >> only one thread left running after panic, that will be the thread that called >> panic, checking TDF_INPANIC just doesn't add anything. > > Won't the scheduler still run even if other CPUs are halted? Is there > any intent to prevent switching to another thread? (I suppose this > could be achieved by setting td_critnest++ and wouldn't require a > flag). > > It's possible I misunderstood your email so my response may have been > non-sensical. No, no, it does make sense. I haven't mentioned this, but yes, new world order with stop_cpus_on_panic==1 implies disabling interrupts for a panic thread. I also took it to mean that there will not be any thread switches, but perhaps I am mistaken here... In any case my intention is to ensure that only the panic thread runs. -- Andriy Gapon
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