Date: Tue, 11 Jan 2022 09:16:46 -0500 From: Mark Johnston <markj@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: Mateusz Guzik <mjguzik@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: Debugging a (potentially?) ZFS-related panic, and discussion about large patchsets Message-ID: <Yd2RTqQxO4JqJ5gr@nuc> In-Reply-To: <1bf39343-c9b2-353c-63e7-8604adc9d391@FreeBSD.org> References: <20220110221116.gustgfgfge6pb5fe@mutt-hbsd> <YdzCatNYBVDFi9So@nuc> <CAGudoHHuNbYNFsc3vqihFkQ0xA9Hojp21-QuHczVXvMVSHfQ5w@mail.gmail.com> <1bf39343-c9b2-353c-63e7-8604adc9d391@FreeBSD.org>
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On Tue, Jan 11, 2022 at 09:28:27AM +0200, Andriy Gapon wrote: > On 11/01/2022 01:43, Mateusz Guzik wrote: > > imo the kernel should be patched to obtain the trace on its own. As > > the target has interrupts disabled it will have to do it with NMI, but > > support for that got scrapped in > > > > commit 1c29da02798d968eb874b86221333a56393a94c3 > > Author: Mark Johnston<markj@FreeBSD.org> > > Date: Fri Jan 31 15:43:33 2020 +0000 > > > > Reimplement stack capture of running threads on i386 and amd64. > > This is an off-topic for the thread, but as far as I recall, even when the stack > capture (e.g., for procstat -k) was implemented using NMI there was a piece of > code in the corresponding NMI handler that skipped the stack tracing if > interrupts were disabled. I don't recall / know why. > You can see that in the removed stack_nmi_handler() that used to be in > sys/x86/x86/stack_machdep.c. I think it may have been to avoid tracing threads in the middle of a context switch, but I can't remember exactly which inconsistencies were problematic.
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