spinlocks and preemption points need to be at least compiler barriers

commit 386afc91144b36b42117b0092893f15bc8798a80 upstream.

In UP and non-preempt respectively, the spinlocks and preemption
disable/enable points are stubbed out entirely, because there is no
regular code that can ever hit the kind of concurrency they are meant to
protect against.

However, while there is no regular code that can cause scheduling, we
_do_ end up having some exceptional (literally!) code that can do so,
and that we need to make sure does not ever get moved into the critical
region by the compiler.

In particular, get_user() and put_user() is generally implemented as
inline asm statements (even if the inline asm may then make a call
instruction to call out-of-line), and can obviously cause a page fault
and IO as a result.  If that inline asm has been scheduled into the
middle of a preemption-safe (or spinlock-protected) code region, we
obviously lose.

Now, admittedly this is *very* unlikely to actually ever happen, and
we've not seen examples of actual bugs related to this.  But partly
exactly because it's so hard to trigger and the resulting bug is so
subtle, we should be extra careful to get this right.

So make sure that even when preemption is disabled, and we don't have to
generate any actual *code* to explicitly tell the system that we are in
a preemption-disabled region, we need to at least tell the compiler not
to move things around the critical region.

This patch grew out of the same discussion that caused commits
79e5f05edcbf ("ARC: Add implicit compiler barrier to raw_local_irq*
functions") and 3e2e0d2c222b ("tile: comment assumption about
__insn_mtspr for <asm/irqflags.h>") to come about.

Note for stable: use discretion when/if applying this.  As mentioned,
this bug may never have actually bitten anybody, and gcc may never have
done the required code motion for it to possibly ever trigger in
practice.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
crypto: gcm - fix assumption that assoc has one segment

commit d3dde52209ab571e4e2ec26c66f85ad1355f7475 upstream.

rfc4543(gcm(*)) code for GMAC assumes that assoc scatterlist always contains
only one segment and only makes use of this first segment. However ipsec passes
assoc with three segments when using 'extended sequence number' thus in this
case rfc4543(gcm(*)) fails to function correctly. Patch fixes this issue.

Reported-by: Chaoxing Lin <Chaoxing.Lin@ultra-3eti.com>
Tested-by: Chaoxing Lin <Chaoxing.Lin@ultra-3eti.com>
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
block: avoid using uninitialized value in from queue_var_store

commit c678ef5286ddb5cf70384ad5af286b0afc9b73e1 upstream.

As found by gcc-4.8, the QUEUE_SYSFS_BIT_FNS macro creates functions
that use a value generated by queue_var_store independent of whether
that value was set or not.

block/blk-sysfs.c: In function 'queue_store_nonrot':
block/blk-sysfs.c:244:385: warning: 'val' may be used uninitialized in this function [-Wmaybe-uninitialized]

Unlike most other such warnings, this one is not a false positive,
writing any non-number string into the sysfs files indeed has
an undefined result, rather than returning an error.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ALSA: hda - bug fix on return value when getting HDMI ELD info

commit 2ef5692efad330b67a234e2c49edad38538751e7 upstream.

In function snd_hdmi_get_eld(), the variable 'ret' should be initialized to 0.
Otherwise it will be returned uninitialized as non-zero after ELD info is got
successfully. Thus hdmi_present_sense() will always assume ELD info is invalid
by mistake, and /proc file system cannot show the proper ELD info.

Signed-off-by: Mengdong Lin <mengdong.lin@intel.com>
Acked-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ALSA: hda - fix typo in proc output

commit aeb3a97222832e5457c4b72d72235098ce4bfe8d upstream.

Rename "Digitial In" to "Digital In". This function is only used for
proc output, so should not cause any problems to change.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ftrace: Consistently restore trace function on sysctl enabling

commit 5000c418840b309251c5887f0b56503aae30f84c upstream.

If we reenable ftrace via syctl, we currently set ftrace_trace_function
based on the previous simplistic algorithm. This is inconsistent with
what update_ftrace_function does. So better call that helper instead.

Link: http://lkml.kernel.org/r/5151D26F.1070702@siemens.com

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add CPUFREQ Abyssplug
cpufreq_abyssplug.c: Fix and Adapt to 3.0 Kernel
printk: Don't allow cpu to get console lock during hotplugging

The flush of the console takes unnecessary time during the cpu
hotplug up operation.  It can delay the rcu synchronize_sched
operation, which in turn delays the hotplug operation. The flush
delays rcu synchronize_sched during scheduling domain creation
by up to 100 ms by interrupting the move to a quiescent state.
This change delays the flush of the console to later in the
notification chain of cpu_online. At the point in the cpu_up
operation where the flush now occurs, other tasks can already
be scheduled on the cpu that just came up.

Signed-off-by: Maya Spivak <mspivak@codeaurora.org>
(cherry picked from commit c7108258d7e44b56842f8215e31d7310f86febaa)

Change-Id: I2986071a5b05760e05d86da2f33ea2a9fe882469
Signed-off-by: Swetha Basineni <sbasin@codeaurora.org>
cpu-hotplug: Add the function 'cpu_hotplug_inprogress'

Allows a caller to detect whether a cpu hotplug operation
is in progress. This is useful for optimizing code paths
based on this condition.

Signed-off-by: Maya Spivak <mspivak@codeaurora.org>
(cherry picked from commit 9f6cabec8fd0d0cb95084d18ee7cddbcf922ac2d)

Change-Id: I2eae7fbb819e3a776dba77a061eb89f30ac3176d
Signed-off-by: Swetha Basineni <sbasin@codeaurora.org>
CPU hotplug, PM: Remove unused symbol 'suspend_cpu_hotplug'

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
ARM: smpboot: Enable interrupts after marking CPU online/active

With the note that we really should clean up the cpu hotplug code,
there's far too much code duplication in the arch/ implementations. The
below patch looks like it might actually work.

Thomas, others, please have a very close look because I might have
thought too hard and missed the obvious :-)

---
Subject: hotplug, sched: cpu_active vs __cpu_up
Stepan found:

CPU0		CPUn

_cpu_up()
  __cpu_up()

		boostrap()
		  notify_cpu_starting()
		  set_cpu_online()
		  while (!cpu_active())
		    cpu_relax()

<PREEMPT-out>

smp_call_function(.wait=1)
  /* we find cpu_online() is true */
  arch_send_call_function_ipi_mask()
  /* wait-forever-more */
<PREEMPT-in>
		  local_irq_enable()

  cpu_notify(CPU_ONLINE)
    sched_cpu_active()
      set_cpu_active()

Now the purpose of cpu_active is mostly with bringing down a cpu, where
we mark it !active to avoid the load-balancer from moving tasks to it
while we tear down the cpu. This is required because we only update the
sched_domain tree after we brought the cpu-down. And this is needed so
that some tasks can still run while we bring it down, we just don't want
new tasks to appear.

On cpu-up however the sched_domain tree doesn't yet include the new cpu,
so its invisible to the load-balancer, regardless of the active state.
So instead of setting the active state after we boot the new cpu (and
consequently having to wait for it before enabling interrupts) set the
cpu active before we set it online and avoid the whole mess.

Reported-by: Stepan Moskovchenko <stepanm@codeaurora.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
backported to linux 3.0.x by faux123
ARM: SMP: use a timing out completion for cpu hotplug

Rather than open-coding the jiffy-based wait, and polling for the
secondary CPU to come online, use a completion instead.  This
removes the need to poll, instead we will be notified when the
secondary CPU has initialized.

Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
ARM: smp: Fix cpu_up() racing with sys_reboot
timer: optimize apply_slack()

__fls(mask) is equivalent to find_last_bit(&mask, BITS_PER_LONG), but cheaper.
find_last_bit was showing up high on the list when I was profiling for stalls
on icache misses on a system with very small cache size (MIPS).

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
config SCHED_AUTOGROUP=y
SCHEDULER: Autogroup patch group by current user android UID instead of task ID
panic: Fix a possible deadlock in panic()

panic_lock is meant to ensure that panic processing takes
place only on one cpu; if any of the other cpus encounter
a panic, they will spin waiting to be shut down.

However, this causes a regression in this scenario:

1. Cpu 0 encounters a panic and acquires the panic_lock
   and proceeds with the panic processing.
2. There is an interrupt on cpu 0 that also encounters
   an error condition and invokes panic.
3. This second invocation fails to acquire the panic_lock
   and enters the infinite while loop in panic_smp_self_stop.

Thus all panic processing is stopped, and the cpu is stuck
for eternity in the while(1) inside panic_smp_self_stop.
To address this, disable local interrupts with
local_irq_disable before acquiring the panic_lock. This will
prevent interrupt handlers from executing during the panic
processing, thus avoiding this particular problem.

Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
ext4: use atomic64_t for the per-flexbg free_clusters count

commit 90ba983f6889e65a3b506b30dc606aa9d1d46cd2 upstream.

A user who was using a 8TB+ file system and with a very large flexbg
size (> 65536) could cause the atomic_t used in the struct flex_groups
to overflow.  This was detected by PaX security patchset:

http://forums.grsecurity.net/viewtopic.php?f=3&t=3289&p=12551#p12551

This bug was introduced in commit 9f24e4208f7e, so it's been around
since 2.6.30.  :-(

Fix this by using an atomic64_t for struct orlav_stats's
free_clusters.

[Backported for 3.0-stable. Renamed free_clusters back to free_blocks;
fixed a few more atomic_read's of free_blocks left in 3.0.]

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Lingzhu Xiang <lxiang@redhat.com>
Reviewed-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ext4: fixup 64-bit divides in 3.0-stable backport of upstream fix

Replace C division operators with div64_u64 for divides introduced in:
commit 503f4bdcc078e7abee273a85ce322de81b18a224
ext4: use atomic64_t for the per-flexbg free_clusters count

Specific to the 3.0-stable backport of the upstream patch.

Change-Id: Id10180ed16f54f58fc18531092e88f52fc6de31c
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Todd Poynor <toddpoynor@google.com>