Date: Tue, 20 Oct 2020 12:30:05 -0400 From: Mark Johnston <markj@freebsd.org> To: bob prohaska <fbsd@www.zefox.net> Cc: mmel@freebsd.org, freebsd-current@freebsd.org, freebsd-arm@freebsd.org Subject: Re: panic: non-current pmap 0xffffa00020eab8f0 on Rpi3 Message-ID: <20201020163005.GD46122@raichu> In-Reply-To: <20201019230909.GA66675@www.zefox.net> References: <20201006021029.GA13260@www.zefox.net> <20201006133743.GA96285@raichu> <c8a5e1d2-0c47-e3f7-300a-f2fce55d2819@freebsd.org> <20201019203954.GC46122@raichu> <20201019230909.GA66675@www.zefox.net>
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On Mon, Oct 19, 2020 at 04:09:09PM -0700, bob prohaska wrote: > On Mon, Oct 19, 2020 at 04:39:54PM -0400, Mark Johnston wrote: > > > > I think vmspace_exit() should issue a release fence with the cmpset and > > an acquire fence when handling the refcnt == 1 case, but I don't see why > > that would make a difference here. So, if you can test a debug patch, > > this one will yield a bit more debug info. If you can provide access to > > a vmcore and kernel debug symbols, that'd be even better. > > > > I haven't seen an invalid pmap panic since the report of October 5th. > Your patch applied cleanly on the Pi3 running HEAD at r366780M, > the M being due to patches supplied by Kyle Evans applied to > M sys/arm/broadcom/bcm2835/bcm2835_mbox.c > M sys/arm/broadcom/bcm2835/bcm2835_sdhci.c > M sys/arm/broadcom/bcm2835/bcm2835_vcbus.c > M sys/arm/broadcom/bcm2835/bcm2835_vcbus.h > > AIUI, they're something to do with DMA for peripherals. They've > caused no obvious trouble, if you anticipate conflicts let me know > and I'll remove them There should be no need to remove them. > I've never seen either a vmcore file or debug symbols on this machine. > A sequence of instructions to generate the data needed would be helpful. I set up a RPi3 to try and repro this and have so far managed to trigger it once using Peter Holm's stress2 suite, so I'll keep investigating. I hadn't configured a dump device, but I was able to confirm from DDB that PCPU_GET(curpmap) == &vmspace0->vm_pmap. For future reference, https://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug.html has some info on configuring a dump device. For the RPi I'm just using a USB stick as the dump device. > Thanks for reading! > > bob prohaska >
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