linux-stable.git, branch v3.4.99

Linux 3.4.99

2014-07-17T22:55:52+00:00

ACPI / battery: Retry to get battery information if failed during probing

2014-07-17T22:39:50+00:00

commit 75646e758a0ecbed5024454507d5be5b9ea9dcbf upstream.

Some machines (eg. Lenovo Z480) ECs are not stable during boot up
and causes battery driver fails to be loaded due to failure of getting
battery information from EC sometimes. After several retries, the
operation will work. This patch is to retry to get battery information 5
times if the first try fails.

[ backport to 3.14.5: removed second parameter in acpi_battery_update(),
introduced by the commit 9e50bc14a7f58b5d8a55973b2d69355852ae2dae (ACPI /
battery: Accelerate battery resume callback)]

[naszar : backport to 3.14.5]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=75581
Reported-and-tested-by: naszar 
Cc: All applicable 
Signed-off-by: Lan Tianyu 
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman

x86, ioremap: Speed up check for RAM pages

2014-07-17T22:39:50+00:00

commit c81c8a1eeede61e92a15103748c23d100880cc8a upstream.

In __ioremap_caller() (the guts of ioremap), we loop over the range of
pfns being remapped and checks each one individually with page_is_ram().
For large ioremaps, this can be very slow.  For example, we have a
device with a 256 GiB PCI BAR, and ioremapping this BAR can take 20+
seconds -- sometimes long enough to trigger the soft lockup detector!

Internally, page_is_ram() calls walk_system_ram_range() on a single
page.  Instead, we can make a single call to walk_system_ram_range()
from __ioremap_caller(), and do our further checks only for any RAM
pages that we find.  For the common case of MMIO, this saves an enormous
amount of work, since the range being ioremapped doesn't intersect
system RAM at all.

With this change, ioremap on our 256 GiB BAR takes less than 1 second.

Signed-off-by: Roland Dreier 
Link: http://lkml.kernel.org/r/1399054721-1331-1-git-send-email-roland@kernel.org
Signed-off-by: H. Peter Anvin 
Signed-off-by: Greg Kroah-Hartman

rtmutex: Plug slow unlock race

2014-07-17T22:39:50+00:00

commit 27e35715df54cbc4f2d044f681802ae30479e7fb upstream.

When the rtmutex fast path is enabled the slow unlock function can
create the following situation:

spin_lock(foo->m->wait_lock);
foo->m->owner = NULL;
	    			rt_mutex_lock(foo->m); <-- fast path
				free = atomic_dec_and_test(foo->refcnt);
				rt_mutex_unlock(foo->m); <-- fast path
				if (free)
				   kfree(foo);

spin_unlock(foo->m->wait_lock); <--- Use after free.

Plug the race by changing the slow unlock to the following scheme:

     while (!rt_mutex_has_waiters(m)) {
     	    /* Clear the waiters bit in m->owner */
	    clear_rt_mutex_waiters(m);
      	    owner = rt_mutex_owner(m);
      	    spin_unlock(m->wait_lock);
      	    if (cmpxchg(m->owner, owner, 0) == owner)
      	       return;
      	    spin_lock(m->wait_lock);
     }

So in case of a new waiter incoming while the owner tries the slow
path unlock we have two situations:

 unlock(wait_lock);
					lock(wait_lock);
 cmpxchg(p, owner, 0) == owner
 	    	   			mark_rt_mutex_waiters(lock);
	 				acquire(lock);

Or:

 unlock(wait_lock);
					lock(wait_lock);
	 				mark_rt_mutex_waiters(lock);
 cmpxchg(p, owner, 0) != owner
					enqueue_waiter();
					unlock(wait_lock);
 lock(wait_lock);
 wakeup_next waiter();
 unlock(wait_lock);
					lock(wait_lock);
					acquire(lock);

If the fast path is disabled, then the simple

   m->owner = NULL;
   unlock(m->wait_lock);

is sufficient as all access to m->owner is serialized via
m->wait_lock;

Also document and clarify the wakeup_next_waiter function as suggested
by Oleg Nesterov.

Reported-by: Steven Rostedt 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Steven Rostedt 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20140611183852.937945560@linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Mike Galbraith 
Signed-off-by: Greg Kroah-Hartman

rtmutex: Handle deadlock detection smarter

2014-07-17T22:39:50+00:00

commit 3d5c9340d1949733eb37616abd15db36aef9a57c upstream.

Even in the case when deadlock detection is not requested by the
caller, we can detect deadlocks. Right now the code stops the lock
chain walk and keeps the waiter enqueued, even on itself. Silly not to
yell when such a scenario is detected and to keep the waiter enqueued.

Return -EDEADLK unconditionally and handle it at the call sites.

The futex calls return -EDEADLK. The non futex ones dequeue the
waiter, throw a warning and put the task into a schedule loop.

Tagged for stable as it makes the code more robust.

Signed-off-by: Thomas Gleixner 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Cc: Brad Mouring 
Link: http://lkml.kernel.org/r/20140605152801.836501969@linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Mike Galbraith 
Signed-off-by: Greg Kroah-Hartman

rtmutex: Detect changes in the pi lock chain

2014-07-17T22:39:50+00:00

commit 82084984383babe728e6e3c9a8e5c46278091315 upstream.

When we walk the lock chain, we drop all locks after each step. So the
lock chain can change under us before we reacquire the locks. That's
harmless in principle as we just follow the wrong lock path. But it
can lead to a false positive in the dead lock detection logic:

T0 holds L0
T0 blocks on L1 held by T1
T1 blocks on L2 held by T2
T2 blocks on L3 held by T3
T4 blocks on L4 held by T4

Now we walk the chain

lock T1 -> lock L2 -> adjust L2 -> unlock T1 ->
     lock T2 ->  adjust T2 ->  drop locks

T2 times out and blocks on L0

Now we continue:

lock T2 -> lock L0 -> deadlock detected, but it's not a deadlock at all.

Brad tried to work around that in the deadlock detection logic itself,
but the more I looked at it the less I liked it, because it's crystal
ball magic after the fact.

We actually can detect a chain change very simple:

lock T1 -> lock L2 -> adjust L2 -> unlock T1 -> lock T2 -> adjust T2 ->

     next_lock = T2->pi_blocked_on->lock;

drop locks

T2 times out and blocks on L0

Now we continue:

lock T2 ->

     if (next_lock != T2->pi_blocked_on->lock)
     	   return;

So if we detect that T2 is now blocked on a different lock we stop the
chain walk. That's also correct in the following scenario:

lock T1 -> lock L2 -> adjust L2 -> unlock T1 -> lock T2 -> adjust T2 ->

     next_lock = T2->pi_blocked_on->lock;

drop locks

T3 times out and drops L3
T2 acquires L3 and blocks on L4 now

Now we continue:

lock T2 ->

     if (next_lock != T2->pi_blocked_on->lock)
     	   return;

We don't have to follow up the chain at that point, because T2
propagated our priority up to T4 already.

[ Folded a cleanup patch from peterz ]

Signed-off-by: Thomas Gleixner 
Reported-by: Brad Mouring 
Cc: Steven Rostedt 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20140605152801.930031935@linutronix.de
Signed-off-by: Mike Galbraith 
Signed-off-by: Greg Kroah-Hartman

rtmutex: Fix deadlock detector for real

2014-07-17T22:39:50+00:00

commit 397335f004f41e5fcf7a795e94eb3ab83411a17c upstream.

The current deadlock detection logic does not work reliably due to the
following early exit path:

	/*
	 * Drop out, when the task has no waiters. Note,
	 * top_waiter can be NULL, when we are in the deboosting
	 * mode!
	 */
	if (top_waiter && (!task_has_pi_waiters(task) ||
			   top_waiter != task_top_pi_waiter(task)))
		goto out_unlock_pi;

So this not only exits when the task has no waiters, it also exits
unconditionally when the current waiter is not the top priority waiter
of the task.

So in a nested locking scenario, it might abort the lock chain walk
and therefor miss a potential deadlock.

Simple fix: Continue the chain walk, when deadlock detection is
enabled.

We also avoid the whole enqueue, if we detect the deadlock right away
(A-A). It's an optimization, but also prevents that another waiter who
comes in after the detection and before the task has undone the damage
observes the situation and detects the deadlock and returns
-EDEADLOCK, which is wrong as the other task is not in a deadlock
situation.

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Reviewed-by: Steven Rostedt 
Cc: Lai Jiangshan 
Link: http://lkml.kernel.org/r/20140522031949.725272460@linutronix.de
Signed-off-by: Thomas Gleixner 
Signed-off-by: Mike Galbraith 
Signed-off-by: Greg Kroah-Hartman

tracing: Remove ftrace_stop/start() from reading the trace file

2014-07-17T22:39:50+00:00

commit 099ed151675cd1d2dbeae1dac697975f6a68716d upstream.

Disabling reading and writing to the trace file should not be able to
disable all function tracing callbacks. There's other users today
(like kprobes and perf). Reading a trace file should not stop those
from happening.

Reviewed-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

drm/radeon: stop poisoning the GART TLB

2014-07-17T22:39:50+00:00

commit 0986c1a55ca64b44ee126a2f719a6e9f28cbe0ed upstream.

When we set the valid bit on invalid GART entries they are
loaded into the TLB when an adjacent entry is loaded. This
poisons the TLB with invalid entries which are sometimes
not correctly removed on TLB flush.

For stable inclusion the patch probably needs to be modified a bit.

Signed-off-by: Christian König 
Signed-off-by: Alex Deucher 
Signed-off-by: Greg Kroah-Hartman

ext4: clarify error count warning messages

2014-07-17T22:39:50+00:00

commit ae0f78de2c43b6fadd007c231a352b13b5be8ed2 upstream.

Make it clear that values printed are times, and that it is error
since last fsck. Also add note about fsck version required.

Signed-off-by: Pavel Machek 
Signed-off-by: Theodore Ts'o 
Reviewed-by: Andreas Dilger 
Signed-off-by: Greg Kroah-Hartman