On Wed, Jun 09, 2004 at 21:52:48 +0200, Tyler wrote: > aksingh@hss.hns.com wrote: > > > > > > > >Hi, > > > > I am implementing a poll function for my char device, there is a standard > >procedure of doing it, > > > >1. poll_wait(give yr wait_queues address here); > > > >2. then see if there is something to be read/write, set a mask and return > >to user. > > > >but here drivers dont seem to add the current process to the waitqueue, > >before calling poll_wait, so does poll_wait does this for them ? > > > >regards > >Amit > > > yes exactly. poll_wait adds a wait queue in the pollwait table of the > kernel. When an event occurs (write of data for example), the process is > awaken. It's not that exact. The original poster seems to assume, that poll_wait sleeps. But it does not. It just gathers the waitqueues. And only when ->poll methods of all watched descriptors have been called, and said they don't have events, only then the process is put to sleep on all those queues at once. ------------------------------------------------------------------------------- Jan 'Bulb' Hudec <bulb@ucw.cz>
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