Date: Tue, 11 Jan 2011 15:50:07 -0500 From: Boris Kochergin <spawk@acm.poly.edu> To: "C. P. Ghost" <cpghost@cordula.ws> Cc: freebsd-current@freebsd.org, d@delphij.net Subject: Re: why panic(9) ? Message-ID: <4D2CC27F.7040206@acm.poly.edu> In-Reply-To: <AANLkTinzWR63aeAhwgwQAMX5-ghfHJ%2BEZ83xb8mH7Tj%2B@mail.gmail.com> References: <AANLkTi=OQbS-0jJx0YwZhM7xDWPLOkaYYZAYfESUEvvM@mail.gmail.com> <4D2CBE45.90209@delphij.net> <AANLkTinzWR63aeAhwgwQAMX5-ghfHJ%2BEZ83xb8mH7Tj%2B@mail.gmail.com>
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On 01/11/11 15:37, C. P. Ghost wrote: > On Tue, Jan 11, 2011 at 9:32 PM, Xin LI<delphij@delphij.net> wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA256 >> >> On 01/11/11 12:11, David DEMELIER wrote: >>> Yes, why this function exists? There is no way to solve a problem >>> without panic'ing? Is panic really needed? Imagine someone working on >> [...] >> >> Panic is used to stop the kernel in an aggressive way when data damage >> is detected and the damage is already beyond what the kernel can recover >> from. >> >> The kernel can and should be made more robust but no, I don't think we >> can totally eliminate panic(). > Exactly. One area where the kernel should be made more robust > is UFS with disappearing disks (e.g. USB mounted file systems, > or, as recently happened here with a loose external SATA cable). > Panicing here is REALLY annoying. ;-) Getting slightly off-topic here, but... there was progress made on this front a while ago. You can reliably detach at least USB storage with a mounted MSDOSFS or UFS filesystem without soft updates and not risk a system panic. There will be a panic if soft updates are enabled on UFS, however, at least as of my last test in 2010. -Boris >> Cheers, >> - -- >> Xin LI<delphij@delphij.net> http://www.delphij.net/ >> FreeBSD - The Power to Serve! Live free or die > -cpghost. >
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