USB stick access freezing up system? - BSD

This is a discussion on USB stick access freezing up system? - BSD ; In article , Richard Tobin wrote: >In article , Bill Vermillion wrote: >>I think a panic on trying to write to a disk that has been >>inadvertantly removed is acceptable. That may be far better >>than having you think something ...

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Thread: USB stick access freezing up system?

  1. Re: USB stick access freezing up system?

    In article ,
    Richard Tobin wrote:
    >In article , Bill Vermillion wrote:


    >>I think a panic on trying to write to a disk that has been
    >>inadvertantly removed is acceptable. That may be far better
    >>than having you think something completed successfully and then
    >>find the end-of-month accounting runs, payroll, some-financials,
    >>etc. in error.


    >Surely payroll systems can report errors in some way other than a
    >kernel panic! Don't they check the result of fwrite() and fclose()?


    Payroll systems using journalling and rollbacks operated ON TOP of
    the OS and they would have nothing to do with a kernel panic.

    >But of course most of us are not running payroll systems anyway.
    >I wouldn't mind if there was a switch to enable panics on disk
    >removal, but I think you'd find the vast majority would leave
    >it in the "off" position.
    >
    >-- Richard
    >--
    >:wq


    Ah - a vi user :-)

    Unix systems traditionally have paniced when something goes wrong -
    and a disk which it thought was mounted but is no langer accessible
    does fit that model.

    The reason for the panic could be summed up as "there is something
    really really wrong and I better just shut the system down before I
    accidentally do more damage to the system".

    From my POV that is a sane approach. An OS run amuck could take
    you to the point where nothing short of a low-level format and a
    compete re-install would bring it back to life.

    IOW 'somethings wrong so let's stop now before it gets worse'.

    Nothing really was removeable when the original Unix systems were
    designed. Well there were the clothes-washer sized 70MB disk
    systems with the 14" disk packs - but you surely couldn't remove
    one of those when things were running unless you were willing
    to sacrifice life or limb to the spinning disks.

    Bill


    --
    Bill Vermillion - bv @ wjv . com

  2. Re: USB stick access freezing up system?

    In article ,
    jpd wrote:

    >> Surely payroll systems can report errors in some way other than a
    >> kernel panic! Don't they check the result of fwrite() and fclose()?


    >Do you think you can afford the cost should your assumptions prove
    >false in the real world? Are you prepared to shell out for it?


    "The real world" is not an argument, it's a slogan. I'm the real world
    just as much as payroll systems.

    >Suppose write() suddenly returns ENXIO (``device not configured''). What
    >would you do? Log an error. Suppose that returns ENXIO? Write a mail.
    >And if THAT return ENXIO (mail program is on a mount that vanished)? Or
    >maybe the program loads fine, but its spool was on the disk that is now
    >gone. Suppose the mail program successfully tells you it gave up. Now
    >what? Print it on stderr? It's a daemon and it doesn't have a controlling
    >tty. Print it on the console, then? Say it's a server, and is headless?


    Do I care? I have a desktop machine and pulled out my flash card full
    of photos. Do I want all my other programs to go away just because
    of some theoretical situation involving payroll programs on a server
    somewhere?

    >Sometimes you really do have to intentionally break things to make sure
    >the people involved will finally get off their lazy arses and do the
    >thing they were supposed to do already.


    I'd rather have a large bank screw up their databases than have my
    home machine reboot unnecessarily.

    >Say you are the sysadmin responsible


    No, say I'm the person I actually am. Why would I want my system
    to screw me for no good reason?

    >In short, that easy ``surely'' of yours, comes with a steep price tag.
    >Are you prepared to pay the cost?


    I'm happy for payroll people to pay whatever it costs them to do
    whatever they care about. I'm not happy for their problem to become
    my problem. Currently, if I use FreeBSD for removable media, I have
    to pay an absurd cost for a small mistake. I'd like to stop paying it.

    It seems to me that you're constructing one-in-a-million situations to
    try to justify a bug from the 70s that's been fixed in dozens of other
    systems.

    -- Richard
    --
    :wq

  3. Re: USB stick access freezing up system?

    In article , Bill Vermillion wrote:

    >>:wq


    >Ah - a vi user :-)


    I think you know that's not true :-)

    >Unix systems traditionally have paniced when something goes wrong -
    >and a disk which it thought was mounted but is no langer accessible
    >does fit that model.


    Yes, absolutely. In the 70s a disk removed without unmounting
    it was probably such a disaster that panicing was at worst the
    lesser of two evils.

    >The reason for the panic could be summed up as "there is something
    >really really wrong and I better just shut the system down before I
    >accidentally do more damage to the system".
    >
    >From my POV that is a sane approach. An OS run amuck could take
    >you to the point where nothing short of a low-level format and a
    >compete re-install would bring it back to life.


    Does a removed disk *really* make the OS run amock? If that was ever
    true, I don't think it is now. It just causes a bunch of reads and
    writes to fail, in much the same way as revoking access to a terminal.
    FreeBSD *does* have a force-unmount.

    If it's the root filesystems, or has an active swap partition, then
    probably some other things will go wrong resulting in a panic, and
    that's quite reasonable. But that's not the usual case.

    >IOW 'somethings wrong so let's stop now before it gets worse'.


    But that's not the typical situation *now*. Typically you've removed
    the USB stick with your photos on it. This does not mean you should
    abort your long-running protein-folding program, or your remote login
    to read mail. I'm not complaining that Thompson and Ritchie made a
    decision 30 years ago, I'm complaining about those who say "it's
    always been that way so it must be right".

    >Nothing really was removeable when the original Unix systems were
    >designed. Well there were the clothes-washer sized 70MB disk
    >systems with the 14" disk packs - but you surely couldn't remove
    >one of those when things were running unless you were willing
    >to sacrifice life or limb to the spinning disks.


    Actually I think you could, but it was a mistake to try and change
    their orientation.

    -- Richard
    --
    :wq

  4. Re: USB stick access freezing up system?

    Richard Tobin wrote:
    > It seems to me that you're constructing one-in-a-million situations to
    > try to justify a bug from the 70s that's been fixed in dozens of other
    > systems.
    >
    > -- Richard


    Not only a bug which has been eliminated everywhere else, but which is
    of no use whatsoever to help the situation in question. In other words
    this bug is not fixed out of laziness (it is indeed complex to solve
    because there are implications in several parts of the system) and
    this laziness is rationalized with totally absurd arguments. I must say
    this sort of bad faith propaganda is more and more widespread in the
    FreeBSD users community.

    --

    Michel TALON


  5. Re: USB stick access freezing up system?

    Begin
    On 9 Dec 2007 22:31:13 GMT, Richard Tobin wrote:
    > In article ,
    > jpd wrote:
    >
    >>> Surely payroll systems can report errors in some way other than a
    >>> kernel panic! Don't they check the result of fwrite() and fclose()?

    >
    >>Do you think you can afford the cost should your assumptions prove
    >>false in the real world? Are you prepared to shell out for it?

    >
    > "The real world" is not an argument, it's a slogan. I'm the real world
    > just as much as payroll systems.


    And if you believe that, I have a bridge to sell you. You did
    conveniently dodge having to say anything of substance there, though.
    Well done.

    Now if you'll excuse me, I'm preferring to not go over your comments
    again, as your reading of what I said I explicitly said differently
    upthread, but instead I will ignore you for a twit and a waste of time.


    --
    j p d (at) d s b (dot) t u d e l f t (dot) n l .
    This message was originally posted on Usenet in plain text.
    Any other representation, additions, or changes do not have my
    consent and may be a violation of international copyright law.

  6. Re: USB stick access freezing up system?

    Getting back to one of the original issues... how can I/O to a umass
    device make FreeBSD - including other processes - grind to a halt?

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