linux-toradex.git/kernel/locking/rtmutex.c, branch v4.14-rc3

locking/rtmutex: replace top-waiter and pi_waiters leftmost caching

2017-09-09T01:26:49+00:00

... with the generic rbtree flavor instead. No changes
in semantics whatsoever.

Link: http://lkml.kernel.org/r/20170719014603.19029-10-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso 
Acked-by: Peter Zijlstra (Intel) 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

locking/rtmutex: Remove unnecessary priority adjustment

2017-07-13T09:44:06+00:00

We don't need to adjust priority before adding a new pi_waiter, the
priority only needs to be updated after pi_waiter change or task
priority change.

Steven Rostedt pointed out:

  "Interesting, I did some git mining and this was added with the original
   entry of the rtmutex.c (23f78d4a03c5). Looking at even that version, I
   don't see the purpose of adjusting the task prio here. It is done
   before anything changes in the task."

Signed-off-by: Alex Shi 
Reviewed-by: Steven Rostedt (VMware) 
Acked-by: Peter Zijlstra (Intel) 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mathieu Poirier 
Cc: Sebastian Siewior 
Cc: Steven Rostedt 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1499926704-28841-1-git-send-email-alex.shi@linaro.org
[ Enhance the changelog. ]
Signed-off-by: Ingo Molnar

locking/rtmutex: Don't initialize lockdep when not required

2017-06-20T09:53:09+00:00

pi_mutex isn't supposed to be tracked by lockdep, but just
passing NULLs for name and key will cause lockdep to spew a
warning and die, which is not what we want it to do.

Skip lockdep initialization if the caller passed NULLs for
name and key, suggesting such initialization isn't desired.

Signed-off-by: Sasha Levin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: f5694788ad8d ("rt_mutex: Add lockdep annotations")
Link: http://lkml.kernel.org/r/20170618140548.4763-1-alexander.levin@verizon.com
Signed-off-by: Ingo Molnar

rt_mutex: Add lockdep annotations

2017-06-08T08:35:49+00:00

Now that (PI) futexes have their own private RT-mutex interface and
implementation we can easily add lockdep annotations to the existing
RT-mutex interface.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

futex,rt_mutex: Fix rt_mutex_cleanup_proxy_lock()

2017-05-22T19:57:18+00:00

Markus reported that the glibc/nptl/tst-robustpi8 test was failing after
commit:

  cfafcd117da0 ("futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock()")

The following trace shows the problem:

 ld-linux-x86-64-2161  [019] ....   410.760971: SyS_futex: 00007ffbeb76b028: 80000875  op=FUTEX_LOCK_PI
 ld-linux-x86-64-2161  [019] ...1   410.760972: lock_pi_update_atomic: 00007ffbeb76b028: curval=80000875 uval=80000875 newval=80000875 ret=0
 ld-linux-x86-64-2165  [011] ....   410.760978: SyS_futex: 00007ffbeb76b028: 80000875  op=FUTEX_UNLOCK_PI
 ld-linux-x86-64-2165  [011] d..1   410.760979: do_futex: 00007ffbeb76b028: curval=80000875 uval=80000875 newval=80000871 ret=0
 ld-linux-x86-64-2165  [011] ....   410.760980: SyS_futex: 00007ffbeb76b028: 80000871 ret=0000
 ld-linux-x86-64-2161  [019] ....   410.760980: SyS_futex: 00007ffbeb76b028: 80000871 ret=ETIMEDOUT

Task 2165 does an UNLOCK_PI, assigning the lock to the waiter task 2161
which then returns with -ETIMEDOUT. That wrecks the lock state, because now
the owner isn't aware it acquired the lock and removes the pending robust
list entry.

If 2161 is killed, the robust list will not clear out this futex and the
subsequent acquire on this futex will then (correctly) result in -ESRCH
which is unexpected by glibc, triggers an internal assertion and dies.

Task 2161			Task 2165

rt_mutex_wait_proxy_lock()
   timeout();
   /* T2161 is still queued in  the waiter list */
   return -ETIMEDOUT;

				futex_unlock_pi()
				spin_lock(hb->lock);
				rtmutex_unlock()
				  remove_rtmutex_waiter(T2161);
				   mark_lock_available();
				/* Make the next waiter owner of the user space side */
				futex_uval = 2161;
				spin_unlock(hb->lock);
spin_lock(hb->lock);
rt_mutex_cleanup_proxy_lock()
  if (rtmutex_owner() !== current)
     ...
     return FAIL;
....
return -ETIMEOUT;

This means that rt_mutex_cleanup_proxy_lock() needs to call
try_to_take_rt_mutex() so it can take over the rtmutex correctly which was
assigned by the waker. If the rtmutex is owned by some other task then this
call is harmless and just confirmes that the waiter is not able to acquire
it.

While there, fix what looks like a merge error which resulted in
rt_mutex_cleanup_proxy_lock() having two calls to
fixup_rt_mutex_waiters() and rt_mutex_wait_proxy_lock() not having any.
Both should have one, since both potentially touch the waiter list.

Fixes: 38d589f2fd08 ("futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock()")
Reported-by: Markus Trippelsdorf 
Bug-Spotted-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Florian Weimer 
Cc: Darren Hart 
Cc: Sebastian Andrzej Siewior 
Cc: Markus Trippelsdorf 
Link: http://lkml.kernel.org/r/20170519154850.mlomgdsd26drq5j6@hirez.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner

rtmutex: Plug preempt count leak in rt_mutex_futex_unlock()

2017-04-05T14:59:37+00:00

mark_wakeup_next_waiter() already disables preemption, doing so again
leaves us with an unpaired preempt_disable().

Fixes: 2a1c60299406 ("rtmutex: Deboost before waking up the top waiter")
Signed-off-by: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/1491379707.6538.2.camel@gmx.de
Signed-off-by: Thomas Gleixner

rtmutex: Fix more prio comparisons

2017-04-04T09:44:07+00:00

There was a pure ->prio comparison left in try_to_wake_rt_mutex(),
convert it to use rt_mutex_waiter_less(), noting that greater-or-equal
is not-less (both in kernel priority view).

This necessitated the introduction of cmp_task() which creates a
pointer to an unnamed stack variable of struct rt_mutex_waiter type to
compare against tasks.

With this, we can now also create and employ rt_mutex_waiter_equal().

Reviewed-and-tested-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Thomas Gleixner 
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.455584638@infradead.org
Signed-off-by: Thomas Gleixner

rtmutex: Fix PI chain order integrity

2017-04-04T09:44:06+00:00

rt_mutex_waiter::prio is a copy of task_struct::prio which is updated
during the PI chain walk, such that the PI chain order isn't messed up
by (asynchronous) task state updates.

Currently rt_mutex_waiter_less() uses task state for deadline tasks;
this is broken, since the task state can, as said above, change
asynchronously, causing the RB tree order to change without actual
tree update -> FAIL.

Fix this by also copying the deadline into the rt_mutex_waiter state
and updating it along with its prio field.

Ideally we would also force PI chain updates whenever DL tasks update
their deadline parameter, but for first approximation this is less
broken than it was.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.403992539@infradead.org
Signed-off-by: Thomas Gleixner

sched/rtmutex: Refactor rt_mutex_setprio()

2017-04-04T09:44:06+00:00

With the introduction of SCHED_DEADLINE the whole notion that priority
is a single number is gone, therefore the @prio argument to
rt_mutex_setprio() doesn't make sense anymore.

So rework the code to pass a pi_task instead.

Note this also fixes a problem with pi_top_task caching; previously we
would not set the pointer (call rt_mutex_update_top_task) if the
priority didn't change, this could lead to a stale pointer.

As for the XXX, I think its fine to use pi_task->prio, because if it
differs from waiter->prio, a PI chain update is immenent.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.303827095@infradead.org
Signed-off-by: Thomas Gleixner

rtmutex: Clean up

2017-04-04T09:44:05+00:00

Previous patches changed the meaning of the return value of
rt_mutex_slowunlock(); update comments and code to reflect this.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.255058238@infradead.org
Signed-off-by: Thomas Gleixner