Date: Sat, 12 Jun 2021 16:45:24 +0200 From: Gary Jennejohn <gljennjohn@gmail.com> To: Edward Tomasz =?ISO-8859-1?Q?Napiera=3Fa?= <trasz@freebsd.org> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: kernel panic while copying files Message-ID: <20210612144524.7881f852@ernst.home> In-Reply-To: <YMSyTC6Z9BJ2dLWe@brick> References: <20210607090109.08ecb130@ernst.home> <YL6Hc6XmEIIx76gt@nuc> <20210608084646.6a7e1bc7@ernst.home> <CANCZdfpODXLP9B%2BAAXSd5dTS4-V_9r%2BEg90z7sz18wTaE8ELZA@mail.gmail.com> <20210608155405.5cf0e200@ernst.home> <20210610095041.38d7597c@ernst.home> <YMSyTC6Z9BJ2dLWe@brick>
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On Sat, 12 Jun 2021 14:10:36 +0100 Edward Tomasz Napiera__a <trasz@freebsd.org> wrote: > On 0610T1150, Gary Jennejohn wrote: > > On Tue, 8 Jun 2021 17:54:05 +0200 > > Gary Jennejohn <gljennjohn@gmail.com> wrote: > > > > [big snip] > > [..] > > > So, I did ``git reset --hard 8dc96b74edb844bb621afeba38fe4af104b13120'', > > which was the penultimate commit made by trasz to clear CCBs on the stack > > after he committed 3394d4239b85b5577845d9e6de4e97b18d3dba58, the change > > to allocate CCBs in UMA. > > > > Note that I only built the kernel and not world. > > > > I tried to reset to 3394d4239b85b5577845d9e6de4e97b18d3dba58 itself, > > but without the following commits for CCBs on the stack the kernel > > paniced during startup in AHCI. > > > > Anyway, this is the minimum set of changes relevant to the uma_ccbs > > story and also results in a panic identical to the one listed above > > when I set kern.cam.da.enable_uma_ccbs=1 and turn on the external USB > > disk. > > > > So, Warner is probably right and at least the da_uma_ccbs commits > > should be reverted until more research can be done on why the panic > > happens. > > > > The ada_uma_ccbs commits do not cause any problems in my experience and > > could probably be left in the kernel. > > Thank you, I'm working on a fix. Meanwhile - does the current code > cause any problems with set kern.cam.da.enable_uma_ccbs set to 0? > If it doesn't, it probably doesn't require backing off, since 0 is > the default, and will keep being the default until bugs such as this > one are fixed. > No, with the sysctl set to 0 it works really well. I've been running it that way for several days and have transferred large amounts of data to an external USB3 disk with no problems. I didn't mention it, but I also tested the reset kernel (with INVARIANTS) with the sysctl set to 0 and the kernel did not panic. I've had ada_enable_uma_ccbs set to 1 the whole time and never saw any problems. I agree, as long as the default is 0 all the code can stay in the tree. -- Gary Jennejohn
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