Messages in this thread | | | Date | Fri, 3 Sep 2004 02:55:38 -0700 | From | William Lee Irwin III <> | Subject | Re: [1/4] standardize bit waiting data type |
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On Fri, Sep 03, 2004 at 11:53:55AM +0200, Martin Wilck wrote: >> Why don't you need a do..while loop any more ? >> There is also no loop in __wait_on_bit() in the completed patch series.
On Fri, Sep 03, 2004 at 02:42:47AM -0700, William Lee Irwin III wrote: > Part of the point of filtered waitqueues is to reestablish wake-one > semantics. This means two things: > (a) those waiting merely for a bit to clear with no need to set it, > i.e. all they want is to know a transition from set to > clear occurred, are only woken once and don't need to loop > waking and sleeping > (b) Of those tasks waiting for a bit to clear so they can set it > exclusively, only one needs to be woken, and after the first > is woken, it promises to clear the bit again, so there is no > need to wake more tasks.
Also, (a) still works in the presence of signals with interruptible waits (which the VM and VFS do not now use); the sleeping function is required to return -EINTR or some other nonzero value to indicate abnormal termination, which in turn must be checked by the caller.
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