Date: Thu, 12 Sep 2013 09:53:36 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Warner Losh <imp@bsdimp.com> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@FreeBSD.org> Subject: Re: Panic mounting root on BeagleBone Black Message-ID: <1379001216.1111.633.camel@revolution.hippie.lan> In-Reply-To: <F85C2A12-21DC-41C6-9037-15AFD0B1AD7E@bsdimp.com> References: <47E403AE-01A2-4AC8-8028-41F0298FAC3E@freebsd.org> <1378997738.1111.631.camel@revolution.hippie.lan> <F85C2A12-21DC-41C6-9037-15AFD0B1AD7E@bsdimp.com>
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On Thu, 2013-09-12 at 09:44 -0600, Warner Losh wrote: > On Sep 12, 2013, at 8:55 AM, Ian Lepore wrote: >=20 > > On Wed, 2013-09-11 at 06:43 -0700, Tim Kientzle wrote: > >> Just built a new image for BBB from SVN r255438. > >>=20 > >> At the second boot, I got this: > >> =10=10 > >> Mounting local file systems:. > >> mmcsd0: Error indicated: 1 Timeout > >> g_vfs_done():mmcsd0s2a[READ(offset=3D2016903168, length=3D4096)]erro= r =3D 5 > >> vnode_pager_getpages: I/O read error > >> vm_fault: pager read error, pid 126 (ps) > >> mmcsd0: Error indicated: 1 Timeout > >> g_vfs_done():mmcsd0s2a[READ(offset=3D131072, length=3D32768)]error =3D= 5 > >> sdhci_ti0-slot0: Got data interrupt 0x00000010, but there is no acti= ve command. > >> sdhci_ti0-slot0: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D REGISTER= DUMP =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > >> sdhci_ti0-slot0: Sys addr: 0x00000000 | Version: 0x00003101 > >> sdhci_ti0-slot0: Blk size: 0x00000200 | Blk cnt: 0x00000010 > >> sdhci_ti0-slot0: Argument: 0x0024679e | Trn mode: 0x0000193a > >> sdhci_ti0-slot0: Present: 0x01f70000 | Host ctl: 0x00000006 > >> sdhci_ti0-slot0: Power: 0x0000000d | Blk gap: 0x00000000 > >> sdhci_ti0-slot0: Wake-up: 0x00000000 | Clock: 0x00000007 > >> sdhci_ti0-slot0: Timeout: 0x0000000d | Int stat: 0x00000000 > >> sdhci_ti0-slot0: Int enab: 0x017f00fb | Sig enab: 0x017f00fb > >> sdhci_ti0-slot0: AC12 err: 0x00000000 | Slot int: 0x00000000 > >> sdhci_ti0-slot0: Caps: 0x06e10080 | Max curr: 0x00000000 > >> sdhci_ti0-slot0: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D > >>=20 > >> =85. few more similar messages, then =85. > >>=20 > >> mmcsd0: Error indicated: 1 Timeout > >> g_vfs_done():mmcsd0s2a[WRITE(offset=3D20808192, length=3D512)]error = =3D 5 > >> g_vfs_done():mmcsd0s2a[WRITE(offset=3D1276346368, length=3D24576)]er= ror =3D 5 > >> panic: brelse: inappropriate B_PAGING or B_CLUSTER bp 0xcd148778 > >> [bt snipped] > >>=20 > >=20 > > This was a single occurance, right? Like you're not dead in the wate= r > > or anything? > >=20 > > There's insanity in that info... the register dump shows a multi-bloc= k > > write (8kbytes) was set up, but the command that timed out was a read. > > If a prior write had timed out why isn't there a g_vfs_done() error > > logged for it? > >=20 > > I think what we really need is some better error recovery in the mmc = and > > sd layers. Retrying a failed IO is cheap and easy. More complex > > recovery is possible too (power cycling and re-intializing the card > > and/or controller). But that has its own difficulties -- what if the > > nature of the problem was that the user swapped cards? -- you don't w= ant > > to retry a write under those conditions. >=20 > I'd disagree with this... Retrying often is the wrong thing to do. If = the write didn't work the first time, why would it work the second? Looks= like a programming bug here in controlling the sdhci controller since we= got errors, then we got an interrupt with no pending commands. This sugg= ests that our timeout isn't quite right... >=20 > Warner >=20 Retrying too often or endlessly is wrong, but IMO so is not retrying at all, especially when the standard specifies error recovery strategies. -- Ian
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