From nobody Tue Jan 11 14:16:46 2022 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id E3B821944E28 for ; Tue, 11 Jan 2022 14:16:50 +0000 (UTC) (envelope-from markjdb@gmail.com) Received: from mail-qt1-x82a.google.com (mail-qt1-x82a.google.com [IPv6:2607:f8b0:4864:20::82a]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1D4" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4JYCS25gzbz4dy5; Tue, 11 Jan 2022 14:16:50 +0000 (UTC) (envelope-from markjdb@gmail.com) Received: by mail-qt1-x82a.google.com with SMTP id s19so18620569qtc.5; Tue, 11 Jan 2022 06:16:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=6KCuWwDoW6FJ3yNfXJMAvbJ+iWwLT7FX+X+SahCwGD0=; b=MQ6FHaNWwi+imL0DHBzAXW561YUQbQEDUDio5J01CriCyT/tiqmlL25qBQbCIjSRNk A+1JBvQQNA/C/XR2+/Tju+V0KTHwUHdhQayrZCQu0k6tLUJrltVRKgiy04nH5KAeUkbM B4OL4i5F5klCzif2YClv1QQa9stv/kkhgkfr2Af46FmtDoH3HFi7RPtQ6QLQYG0dyYb+ UxP97MKBNaj6pkN+5DikjbOtgeKaHFqii9zHFDba+TXfqU+/2L4m0nW1pahvqD9Suphq vKshd31vz22/E85sZ0akOpMsd7dyhXIiyYXv5WxvhEYAOR+n2yLsFmRXOlijJGFNAWDx fOUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=6KCuWwDoW6FJ3yNfXJMAvbJ+iWwLT7FX+X+SahCwGD0=; b=L/IP0CqkcfZdz7rNIuAr5W/vdLuf540iMYRd3uRewhPjrLJp0kArsFSYI/CSPRIWkN pQ0JpHVbR29TnamlqpJuPS5KPFb9Kz9DAo0YOtpgwYL57BMCIK+DS3aKZHcIj5Q22u2U Q3mCaIMB7t5WZoCcg1aPi8YSnf6TlpcIydCq+oCDtjzrg+eoEi/+0khAacRYc+3yyLwd uXdNqHn/j3p1xHM+LIO8TnUc22M70UJ45hbzkHJLznd4lxwB4HfaTpeR3VWmO2fJRipI aCBk4HqiI/i7VTnq0mWl+EoIyElawvfuoWSvIsjLe2u0Kow1QnBztn48zYzhuS/hQjRo AiEA== X-Gm-Message-State: AOAM533G6LRHwNgAPx0MwGl2N5Dv9VIlTGLcZxRqlZ+/ATwn6RiQTBEk J3Xp9Na4OYLaIQPb9hyuNHM2j8SqfIU= X-Google-Smtp-Source: ABdhPJyPEa+rG9Ovd0P4Sx2zZpOuLJR/cRi/1ktS+WUCFH8QlUmAEcPFW2tF3wvSsggJlNPRlOSjmA== X-Received: by 2002:a05:622a:120b:: with SMTP id y11mr3729766qtx.11.1641910609857; Tue, 11 Jan 2022 06:16:49 -0800 (PST) Received: from nuc (198-84-189-58.cpe.teksavvy.com. [198.84.189.58]) by smtp.gmail.com with ESMTPSA id de39sm6367502qkb.5.2022.01.11.06.16.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 Jan 2022 06:16:49 -0800 (PST) Date: Tue, 11 Jan 2022 09:16:46 -0500 From: Mark Johnston To: Andriy Gapon Cc: Mateusz Guzik , freebsd-hackers@freebsd.org Subject: Re: Debugging a (potentially?) ZFS-related panic, and discussion about large patchsets Message-ID: References: <20220110221116.gustgfgfge6pb5fe@mutt-hbsd> <1bf39343-c9b2-353c-63e7-8604adc9d391@FreeBSD.org> List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1bf39343-c9b2-353c-63e7-8604adc9d391@FreeBSD.org> X-Rspamd-Queue-Id: 4JYCS25gzbz4dy5 X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N 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 > > 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.