linux-kernel - Re: [PATCH] sched/wait: introduce wait_event_freezable

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Date:   Fri, 18 Jan 2019 08:48:37 +0100
From:   Hugo Lefeuvre <hle@....eu.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     devel@...verdev.osuosl.org, Todd Kjos <tkjos@...roid.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Greg Hartman <ghartman@...gle.com>,
        linux-kernel@...r.kernel.org,
        Arve Hjønnevåg <arve@...roid.com>,
        Ingo Molnar <mingo@...hat.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Martijn Coenen <maco@...roid.com>,
        Alistair Strachan <strachan@...gle.com>,
        Christian Brauner <christian@...uner.io>
Subject: Re: [PATCH] sched/wait: introduce wait_event_freezable_hrtimeout

Hi Greg,

> > introduce wait_event_freezable_hrtimeout, an interruptible and freezable
> > version of wait_event_hrtimeout.
> > 
> > simplify handle_vsoc_cond_wait (drivers/staging/android/vsoc.c) using this
> > newly added helper and remove useless includes.
> > 
> > Signed-off-by: Hugo Lefeuvre <hle@....eu.com>
> > ---
> >  drivers/staging/android/vsoc.c | 69 +++++-----------------------------
> >  include/linux/wait.h           | 25 ++++++++++--
> 
> code in drivers/staging/ should be self-contained, and not, if at all
> possible, ever force additional changes on "core" kernel code.
> 
> Are you sure that the vsoc code can't use one of the current wait
> macros?

As far as I know there is no macro implementing freezable wait with high
resolution timeout.

> Why is it so special and unique that no one else in the kernel
> has ever needed this before it came along?

many wait_event_X() (_exclusive, _interruptible, _timeout) functions have a
freezable counterpart. wait_event_hrtimeout() doesn't, probably because it
is relatively new (and seemingly quite unused).

If there is a wait_event_hrtimeout() function, it makes sense to me to have
wait_event_freezable_hrtimeout().

-- 
                Hugo Lefeuvre (hle)    |    www.owl.eu.com
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