Messages in this thread |  | | Date | Tue, 17 Jun 2014 07:32:15 -0400 | From | Peter Hurley <> | Subject | Re: [PATCH tty-next 14/22] tty: Remove tty_wait_until_sent_from_close() |
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On 06/17/2014 07:03 AM, David Laight wrote: > From: Peter Hurley > ... >>> I don't understand the second half of the changelog, it doesn't seem >>> to fit here: there deadlock that we are trying to avoid here happens >>> when the *same* tty needs the lock to complete the function that >>> sends the pending data. I don't think we do still do that any more, >>> but it doesn't seem related to the tty lock being system-wide or not. >> >> The tty lock is not used in the i/o path; it's purpose is to >> mutually exclude state changes in open(), close() and hangup(). >> >> The commit that added this [1] comments that _other_ ttys may wait >> for this tty to complete, and comments in the code note that this >> function should be removed when the system-wide tty mutex was removed >> (which happened with the commit noted in the changelog). > > What happens if another process tries to do a non-blocking open > while you are sleeping in close waiting for output to drain? > > Hopefully this returns before that data has drained.
Good point.
tty_open() should be trylocking both mutexes anyway in O_NONBLOCK.
Regards, Peter Hurley
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