:> * Stephen McKay <[EMAIL PROTECTED]> [000805 08:49] wrote:
:> > 
:> > Patch 2 is smaller and possibly controversial.  Normally bufdaemon and
:> > syncer are sleeping when they are told to suspend.  This delays shutdown
:> > by a few boring seconds.  With this patch, it is zippier.  I expect people
:> > to complain about this shortcut, but every sleeping process should expect
:> > to be woken for no reason at all.  Basic kernel premise.
:> You better bet it's controversial, this isn't "Basic kernel premise"
:Actually, that depends.  It is definitely poor programming practice to 
:not check the condition for which you slept on wakeup.
:> *boom* *crash* *ow* :)
:Doctor:  So don't do that.

    I gotta agree.  This is very bad programming practice.  There are many,
    many places in the kernel where tsleep() is called with a 0 delay and
    assumed not to return until something meaningful happens.  For example,
    for handling NFS retries, some of the locking code (I think), and I
    could probably find many others.

    In general 'quick hacks' only cause immense pain later on... sometimes
    years later on.  It is NOT WORTH IT.

    In the case of buf_daemon, waking up the process is a definite no-no. 
    You can wakeup &lbolt, but you can't just go wakeup the process 
    willy-nilly -- it could be sitting anywhere.

    What I would suggest is to add another argument to the shutdown
    event-handler registration, an optional wakeup address.  If NULL,
    no wakeup is performed.  Otherwise a wakeup on the specified address
    is performed.  You can then pass &lbolt to it when the syncer & 
    buf_daemon processes register.  That is a simple, safe solution.


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