wait: add wait_event_hrtimeout()
authorKent Overstreet <koverstreet@google.com>
Tue, 7 May 2013 23:18:43 +0000 (16:18 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 8 May 2013 01:38:28 +0000 (18:38 -0700)
commit774a08b3548f3f4f36c1a4f2a29a1b3710a2c939
treefddb989d580444aaae64a5904f029cc86fe23de9
parent36f5588905c10a8c4568a210d601fe8c3c27e0f0
wait: add wait_event_hrtimeout()

Analagous to wait_event_timeout() and friends, this adds
wait_event_hrtimeout() and wait_event_interruptible_hrtimeout().

Note that unlike the versions that use regular timers, these don't
return the amount of time remaining when they return - instead, they
return 0 or -ETIME if they timed out.  because I was uncomfortable with
the semantics of doing it the other way (that I could get it right,
anyways).

If the timer expires, there's no real guarantee that expire_time -
current_time would be <= 0 - due to timer slack certainly, and I'm not
sure I want to know the implications of the different clock bases in
hrtimers.

If the timer does expire and the code calculates that the time remaining
is nonnegative, that could be even worse if the calling code then reuses
that timeout.  Probably safer to just return 0 then, but I could imagine
weird bugs or at least unintended behaviour arising from that too.

I came to the conclusion that if other users end up actually needing the
amount of time remaining, the sanest thing to do would be to create a
version that uses absolute timeouts instead of relative.

[akpm@linux-foundation.org: fix description of `timeout' arg]
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/wait.h