Re: [PATCH v4.4.y] futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock()

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Hi Greg,

On Fri, Mar 8, 2019 at 3:01 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Mar 07, 2019 at 03:59:04PM -0800, Zubin Mithra wrote:
> > From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> >
> > commit 38d589f2fd08f1296aea3ce62bebd185125c6d81 upstream
> >
> > With the ultimate goal of keeping rt_mutex wait_list and futex_q waiters
> > consistent it's necessary to split 'rt_mutex_futex_lock()' into finer
> > parts, such that only the actual blocking can be done without hb->lock
> > held.
> >
> > Split split_mutex_finish_proxy_lock() into two parts, one that does the
> > blocking and one that does remove_waiter() when the lock acquire failed.
> >
> > When the rtmutex was acquired successfully the waiter can be removed in the
> > acquisiton path safely, since there is no concurrency on the lock owner.
> >
> > This means that, except for futex_lock_pi(), all wait_list modifications
> > are done with both hb->lock and wait_lock held.
> >
> > [bigeasy@xxxxxxxxxxxxx: fix for futex_requeue_pi_signal_restart]
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > Cc: juri.lelli@xxxxxxx
> > Cc: bigeasy@xxxxxxxxxxxxx
> > Cc: xlpang@xxxxxxxxxx
> > Cc: rostedt@xxxxxxxxxxx
> > Cc: mathieu.desnoyers@xxxxxxxxxxxx
> > Cc: jdesfossez@xxxxxxxxxxxx
> > Cc: dvhart@xxxxxxxxxxxxx
> > Cc: bristot@xxxxxxxxxx
> > Link: http://lkml.kernel.org/r/20170322104152.001659630@xxxxxxxxxxxxx
> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Signed-off-by: Zubin Mithra <zsm@xxxxxxxxxxxx>
> > ---
> >  kernel/futex.c                  |  7 +++--
> >  kernel/locking/rtmutex.c        | 52 ++++++++++++++++++++++++++++-----
> >  kernel/locking/rtmutex_common.h |  9 ++++--
> >  3 files changed, 56 insertions(+), 12 deletions(-)
>
> Why is this needed for 4.4.y and not 4.9.y?  What bug/issue does it
> resolve?
>
> From the changelog text, all it looks like it is doing here is
> reorganizing the code a bit.
>
> confused,
>

Was this clarified with v2, or do you still have questions/concerns ?

Thanks,
Guenter



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