Messages in this thread |  | | Date | Mon, 18 Nov 2013 15:27:46 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH/RFC] wait_for_completion_timeout() considered harmful. |
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On Sun, 17 Nov 2013 08:06:03 +1100 NeilBrown <neilb@suse.de> wrote:
> It would be reasonable to assume that > > wait_for_completion_timeout(&wm8350->auxadc_done, msecs_to_jiffies(5)); > > would wait at least 5 msecs for the auxadc_done to complete. But it does not. > With a HZ of 200 or less, msecs_to_jiffies(5) has value '1', and so this > will only wait until the next "timer tick", which could happen immediately. > > This can lead to incorrect results - and has done so in out-of-tree patches > for drivers/misc/bmp085.c which uses a very similar construct to enable interrupt > based result collection. > > The documentation for several *_timeout* functions claim they will wait for > "timeout jiffies" to have elapsed where this is not the case. They will > actually wait for "timeout" jiffies to have started implying an elapsed time > between (timeout-1) and (timeout). > > This patch corrects some of this documentation, and adds a collection of > wait_for_completion*_msecs() > interfaces which wait at least the given number of milliseconds for the > completion (or a signal).
Mutter. wait_for_x(..., 5ms) should wait for a minimum of 5ms, no matter what.
So I'd suggest we make that happen, rather than adding some new interfaces?
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