This patch adds latency tracing for critical timings
(how long interrupts are disabled for).

 "irqsoff" is added to /debugfs/tracing/available_tracers

Note:
  tracing_max_latency
    also holds the max latency for irqsoff (in usecs).
   (default to large number so one must start latency tracing)

  tracing_thresh
    threshold (in usecs) to always print out if irqs off
    is detected to be longer than stated here.
    If irq_thresh is non-zero, then max_irq_latency
    is ignored.

Here's an example of a trace with ftrace_enabled = 0

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
Signed-off-by: Ingo Molnar <mingo@elte.hu>
--------------------------------------------------------------------
 latency: 100 us, #3/3, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
 swapper-0     1d.s3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1d.s3  100us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1d.s3  100us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)

vim:ft=help
=======

And this is a trace with ftrace_enabled == 1

=======
preemption latency trace v1.1.5 on 2.6.24-rc7
--------------------------------------------------------------------
 latency: 102 us, #12/12, CPU#1 | (M:rt VP:0, KP:0, SP:0 HP:0 #P:2)
    -----------------
    | task: swapper-0 (uid:0 nice:0 policy:0 rt_prio:0)
    -----------------
 => started at: _spin_lock_irqsave+0x2a/0xb7
 => ended at:   _spin_unlock_irqrestore+0x32/0x5f

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
 swapper-0     1dNs3    0us+: _spin_lock_irqsave+0x2a/0xb7 (e1000_update_stats+0x47/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_read_phy_reg+0x16/0x225 [e1000] (e1000_update_stats+0x5e2/0x64c [e1000])
 swapper-0     1dNs3   46us : e1000_swfw_sync_acquire+0x10/0x99 [e1000] (e1000_read_phy_reg+0x49/0x225 [e1000])
 swapper-0     1dNs3   46us : e1000_get_hw_eeprom_semaphore+0x12/0xa6 [e1000] (e1000_swfw_sync_acquire+0x36/0x99 [e1000])
 swapper-0     1dNs3   47us : __const_udelay+0x9/0x47 (e1000_read_phy_reg+0x116/0x225 [e1000])
 swapper-0     1dNs3   47us+: __delay+0x9/0x50 (__const_udelay+0x45/0x47)
 swapper-0     1dNs3   97us : preempt_schedule+0xc/0x84 (__delay+0x4e/0x50)
 swapper-0     1dNs3   98us : e1000_swfw_sync_release+0xc/0x55 [e1000] (e1000_read_phy_reg+0x211/0x225 [e1000])
 swapper-0     1dNs3   99us+: e1000_put_hw_eeprom_semaphore+0x9/0x35 [e1000] (e1000_swfw_sync_release+0x50/0x55 [e1000])
 swapper-0     1dNs3  101us : _spin_unlock_irqrestore+0xe/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : _spin_unlock_irqrestore+0x32/0x5f (e1000_update_stats+0x641/0x64c [e1000])
 swapper-0     1dNs3  102us : trace_hardirqs_on_caller+0x75/0x89 (_spin_unlock_irqrestore+0x32/0x5f)

vim:ft=help
=======

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Add each lock class to the all_lock_classes list when it is
first registered.

Previously, lock classes were added to all_lock_classes when
the lock class was first used.  Since one of the uses of the
list is to find unused locks, this didn't work well.

Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

this patch extends the soft-lockup detector to automatically
detect hung TASK_UNINTERRUPTIBLE tasks. Such hung tasks are
printed the following way:

 ------------------>
 INFO: task prctl:3042 blocked for more than 120 seconds.
 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message
 prctl         D fd5e3793     0  3042   2997
        f6050f38 00000046 00000001 fd5e3793 00000009 c06d8264 c06dae80 00000286
        f6050f40 f6050f00 f7d34d90 f7d34fc8 c1e1be80 00000001 f6050000 00000000
        f7e92d00 00000286 f6050f18 c0489d1a f6050f40 00006605 00000000 c0133a5b
 Call Trace:
  [<c04883a5>] schedule_timeout+0x6d/0x8b
  [<c04883d8>] schedule_timeout_uninterruptible+0x15/0x17
  [<c0133a76>] msleep+0x10/0x16
  [<c0138974>] sys_prctl+0x30/0x1e2
  [<c0104c52>] sysenter_past_esp+0x5f/0xa5
  =======================
 2 locks held by prctl/3042:
 #0:  (&sb->s_type->i_mutex_key#5){--..}, at: [<c0197d11>] do_fsync+0x38/0x7a
 #1:  (jbd_handle){--..}, at: [<c01ca3d2>] journal_start+0xc7/0xe9
 <------------------

the current default timeout is 120 seconds. Such messages are printed
up to 10 times per bootup. If the system has crashed already then the
messages are not printed.

if lockdep is enabled then all held locks are printed as well.

this feature is a natural extension to the softlockup-detector (kernel
locked up without scheduling) and to the NMI watchdog (kernel locked up
with IRQs disabled).

[ Gautham R Shenoy <ego@in.ibm.com>: CPU hotplug fixes. ]
[ Andrew Morton <akpm@linux-foundation.org>: build warning fix. ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

Michael Wu noticed in his lkml post at

    http://marc.info/?l=linux-kernel&m=119396182726091&w=2



that certain wireless drivers ended up having their name in module
memory, which would then crash the kernel on module unload.

The patch he proposed was a bit clumsy in that it increased the size of
a lockdep entry significantly; the patch below tries another approach,
it checks, on module teardown, if the name of a class is in module space
and then zaps the class.  This is very similar to what we already do
with keys that are in module space.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Lockdep, during self-test (when it was simulating double unlocks) was
sometimes unconditionally unlocking a spinlock when it had not been
locked. This won't work for ticket locks.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

make cli/sti annotation warnings easier to interpret.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

Torsten Kaiser wrote:

| static inline int in_range(const void *start, const void *addr, const void *end)
| {
|         return addr >= start && addr <= end;
| }
| This  will return true, if addr is in the range of start (including)
| to end (including).
|
| But debug_check_no_locks_freed() seems does:
| const void *mem_to = mem_from + mem_len
| -> mem_to is the last byte of the freed range, that fits in_range
| lock_from = (void *)hlock->instance;
| -> first byte of the lock
| lock_to = (void *)(hlock->instance + 1);
| -> first byte of the next lock, not last byte of the lock that is being checked!
|
| The test is:
| if (!in_range(mem_from, lock_from, mem_to) &&
|                                         !in_range(mem_from, lock_to, mem_to))
|                         continue;
| So it tests, if the first byte of the lock is in the range that is freed ->OK
| And if the first byte of the *next* lock is in the range that is freed
| -> Not OK.

We can also simplify in_range checks, we need only 2 comparisons, not 4.
If the lock is not in memory range, it should be either at the left of range
or at the right.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

fix the oops that can be seen in:

   http://bugzilla.kernel.org/attachment.cgi?id=13828&action=view



it is not safe to print the locks of running tasks.

(even with this fix we have a small race - but this is a debug
 function after all.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

Fix a typo in the __lock_acquire comment.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

The task_struct->pid member is going to be deprecated, so start
using the helpers (task_pid_nr/task_pid_vnr/task_pid_nr_ns) in
the kernel.

The first thing to start with is the pid, printed to dmesg - in
this case we may safely use task_pid_nr(). Besides, printks produce
more (much more) than a half of all the explicit pid usage.

[akpm@linux-foundation.org: git-drm went and changed lots of stuff]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In the following scenario:

code path 1:
  my_function() -> lock(L1); ...; flush_workqueue(); ...

code path 2:
  run_workqueue() -> my_work() -> ...; lock(L1); ...

you can get a deadlock when my_work() is queued or running
but my_function() has acquired L1 already.

This patch adds a pseudo-lock to each workqueue to make lockdep
warn about this scenario.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Provide a check to validate that we do not hold any locks when switching
back to user-space.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

It is possible for the current->curr_chain_key to become inconsistent with the
current index if the chain fails to validate.  The end result is that future
lock_acquire() operations may inadvertently fail to find a hit in the cache
resulting in a new node being added to the graph for every acquire.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

When I started adding support for lockdep to 64-bit powerpc, I got a
lockdep_init_error and with this patch was able to pinpoint why and where
to put lockdep_init().  Let's support this generally for others adding
lockdep support to their architecture.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

    __acquire
        |
       lock _____
        |        \
        |    __contended
        |         |
        |        wait
        | _______/
        |/
        |
   __acquired
        |
   __release
        |
     unlock

We measure acquisition and contention bouncing.

This is done by recording a cpu stamp in each lock instance.

Contention bouncing requires the cpu stamp to be set on acquisition. Hence we
move __acquired into the generic path.

__acquired is then used to measure acquisition bouncing by comparing the
current cpu with the old stamp before replacing it.

__contended is used to measure contention bouncing (only useful for preemptable
locks)

[akpm@linux-foundation.org: cleanups]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

 - update the copyright notices
 - use the default hash function
 - fix a thinko in a BUILD_BUG_ON
 - add a WARN_ON to spot inconsitent naming
 - fix a termination issue in /proc/lock_stat

[akpm@linux-foundation.org: cleanups]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Present all this fancy new lock statistics information:

*warning, _wide_ output ahead*

(output edited for purpose of brevity)

 # cat /proc/lock_stat
lock_stat version 0.1
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
                              class name    contentions   waittime-min   waittime-max waittime-total   acquisitions   holdtime-min   holdtime-max holdtime-total
-----------------------------------------------------------------------------------------------------------------------------------------------------------------

                         &inode->i_mutex:         14458           6.57      398832.75     2469412.23        6768876           0.34    11398383.65   339410830.89
                         ---------------
                         &inode->i_mutex           4486          [<ffffffff802a08f9>] pipe_wait+0x86/0x8d
                         &inode->i_mutex              0          [<ffffffff802a01e8>] pipe_write_fasync+0x29/0x5d
                         &inode->i_mutex              0          [<ffffffff802a0e18>] pipe_read+0x74/0x3a5
                         &inode->i_mutex              0          [<ffffffff802a1a6a>] do_lookup+0x81/0x1ae

.................................................................................................................................................................

              &inode->i_data.tree_lock-W:           491           0.27          62.47         493.89        2477833           0.39         468.89     1146584.25
              &inode->i_data.tree_lock-R:            65           0.44           4.27          48.78       26288792           0.36         184.62    10197458.24
              --------------------------
                &inode->i_data.tree_lock             46          [<ffffffff80277095>] __do_page_cache_readahead+0x69/0x24f
                &inode->i_data.tree_lock             31          [<ffffffff8026f9fb>] add_to_page_cache+0x31/0xba
                &inode->i_data.tree_lock              0          [<ffffffff802770ee>] __do_page_cache_readahead+0xc2/0x24f
                &inode->i_data.tree_lock              0          [<ffffffff8026f6e4>] find_get_page+0x1a/0x58

.................................................................................................................................................................

                      proc_inum_idr.lock:             0           0.00           0.00           0.00             36           0.00          65.60         148.26
                        proc_subdir_lock:             0           0.00           0.00           0.00        3049859           0.00         106.81     1563212.42
                        shrinker_rwsem-W:             0           0.00           0.00           0.00              5           0.00           1.73           3.68
                        shrinker_rwsem-R:             0           0.00           0.00           0.00            633           2.57         246.57       10909.76

'contentions' and 'acquisitions' are the number of such events measured (since
the last reset). The waittime- and holdtime- (min, max, total) numbers are
presented in microseconds.

If there are any contention points, the lock class is presented in the block
format (as i_mutex and tree_lock above), otherwise a single line of output is
presented.

The output is sorted on absolute number of contentions (read + write), this
should get the worst offenders presented first, so that:

 # grep : /proc/lock_stat | head

will quickly show who's bad.

The stats can be reset using:

 # echo 0 > /proc/lock_stat

[bunk@stusta.de: make 2 functions static]
[akpm@linux-foundation.org: fix printk warning]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Introduce the core lock statistics code.

Lock statistics provides lock wait-time and hold-time (as well as the count
of corresponding contention and acquisitions events). Also, the first few
call-sites that encounter contention are tracked.

Lock wait-time is the time spent waiting on the lock. This provides insight
into the locking scheme, that is, a heavily contended lock is indicative of
a too coarse locking scheme.

Lock hold-time is the duration the lock was held, this provides a reference for
the wait-time numbers, so they can be put into perspective.

  1)
    lock
  2)
    ... do stuff ..
    unlock
  3)

The time between 1 and 2 is the wait-time. The time between 2 and 3 is the
hold-time.

The lockdep held-lock tracking code is reused, because it already collects locks
into meaningful groups (classes), and because it is an existing infrastructure
for lock instrumentation.

Currently lockdep tracks lock acquisition with two hooks:

  lock()
    lock_acquire()
    _lock()

 ... code protected by lock ...

  unlock()
    lock_release()
    _unlock()

We need to extend this with two more hooks, in order to measure contention.

  lock_contended() - used to measure contention events
  lock_acquired()  - completion of the contention

These are then placed the following way:

  lock()
    lock_acquire()
    if (!_try_lock())
      lock_contended()
      _lock()
      lock_acquired()

 ... do locked stuff ...

  unlock()
    lock_release()
    _unlock()

(Note: the try_lock() 'trick' is used to avoid instrumenting all platform
       dependent lock primitive implementations.)

It is also possible to toggle the two lockdep features at runtime using:

  /proc/sys/kernel/prove_locking
  /proc/sys/kernel/lock_stat

(esp. turning off the O(n^2) prove_locking functionaliy can help)

[akpm@linux-foundation.org: build fixes]
[akpm@linux-foundation.org: nuke unneeded ifdefs]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Move code around to get fewer but larger #ifdef sections.  Break some
in-function #ifdefs out into their own functions.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Ensure that all of the lock dependency tracking code is under
CONFIG_PROVE_LOCKING.  This allows us to use the held lock tracking code for
other purposes.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

KSYM_NAME_LEN is peculiar in that it does not include the space for the
trailing '\0', forcing all users to use KSYM_NAME_LEN + 1 when allocating
buffer.  This is nonsense and error-prone.  Moreover, when the caller
forgets that it's very likely to subtly bite back by corrupting the stack
because the last position of the buffer is always cleared to zero.

This patch increments KSYM_NAME_LEN by one and updates code accordingly.

* off-by-one bug in asm-powerpc/kprobes.h::kprobe_lookup_name() macro
  is fixed.

* Where MODULE_NAME_LEN and KSYM_NAME_LEN were used together,
  MODULE_NAME_LEN was treated as if it didn't include space for the
  trailing '\0'.  Fix it.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Paulo Marques <pmarques@grupopie.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

It looks like a remainder from designing...

Signed-off-by: Jarek Poplawski <jarkao@o2.pl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Several kallsyms_lookup() pass dummy arguments but only need, say, module's
name.  Make kallsyms_lookup() accept NULLs where possible.

Also, makes picture clearer about what interfaces are needed for all symbol
resolving business.

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Simplify the stacktrace code:

 - remove the unused task argument to save_stack_trace, it's always
   current
 - remove the all_contexts flag, it's alwasy 0

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Andi Kleen <ak@suse.de>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lockdep's data shouldn't be used when debug_locks == 0 because it's not
updated after this, so it's more misleading than helpful.

PS: probably lockdep's current-> fields should be reset after it turns
debug_locks off: so, after printing a bug report, but before return from
exported functions, but there are really a lot of these possibilities (e.g.
 after DEBUG_LOCKS_WARN_ON), so, something could be missed.  (Of course
direct use of this fields isn't recommended either.)

Reported-by: Folkert van Heusden <folkert@vanheusden.com>
Inspired-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lockdep_init() is marked __init but used in several places
outside __init code. This causes following warnings:
$ scripts/mod/modpost kernel/lockdep.o
WARNING: kernel/built-in.o - Section mismatch: reference to .init.text:lockdep_init from .text.lockdep_init_map after 'lockdep_init_map' (at offset 0x105)
WARNING: kernel/built-in.o - Section mismatch: reference to .init.text:lockdep_init from .text.lockdep_reset_lock after 'lockdep_reset_lock' (at offset 0x35)
WARNING: kernel/built-in.o - Section mismatch: reference to .init.text:lockdep_init from .text.__lock_acquire after '__lock_acquire' (at offset 0xb2)

The warnings are less obviously due to heavy inlining by gcc - this is not
altered.

Fix the section mismatch warnings by removing the __init marking, which
seems obviously wrong.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In __lock_acquire check_chain_key can turn off debug_locks, so check is
needed to assure proper return code.

Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Generate locking graph information into /proc/lockdep, for lock hierarchy
documentation and visualization purposes.

sample output:

 c089fd5c OPS:     138 FD:   14 BD:    1 --..: &tty->termios_mutex
  -> [c07a3430] tty_ldisc_lock
  -> [c07a37f0] &port_lock_key
  -> [c07afdc0] &rq->rq_lock_key#2

The lock classes listed are all the first-hop lock dependencies that
lockdep has seen so far.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

- returns after DEBUG_LOCKS_WARN_ON added in 3 places

- debug_locks checking after lookup_chain_cache() added in
  __lock_acquire()

- locking for testing and changing global variable max_lockdep_depth
  added in __lock_acquire()

From: Ingo Molnar <mingo@elte.hu>

My __acquire_lock() cleanup introduced a locking bug: on SMP systems we'd
release a non-owned graph lock.  Fix this by moving the graph unlock back,
and by leaving the max_lockdep_depth variable update possibly racy.  (we
dont care, it's just statistics)

Also add some minimal debugging code to graph_unlock()/graph_lock(),
which caught this locking bug.

Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/lockdep.c: In function `lookup_chain_cache':
kernel/lockdep.c:1339: warning: long long unsigned int format, u64 arg (arg 2)
kernel/lockdep.c:1344: warning: long long unsigned int format, u64 arg (arg 2)

Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Jarek Poplawski noticed that lockdep global state could be accessed in a
racy way if one CPU did a lockdep assert (shutting lockdep down), while the
other CPU would try to do something that changes its global state.

This patch fixes those races and cleans up lockdep's internal locking by
adding a graph_lock()/graph_unlock()/debug_locks_off_graph_unlock helpers.

(Also note that as we all know the Linux kernel is, by definition, bug-free
and perfect, so this code never triggers, so these fixes are highly
theoretical.  I wrote this patch for aesthetic reasons alone.)

[akpm@osdl.org: build fix]
[jarkao2@o2.pl: build fix's refix]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

When we print an assert due to scheduling-in-atomic bugs, and if lockdep
is enabled, then the IRQ tracing information of lockdep can be printed
to pinpoint the code location that disabled interrupts. This saved me
quite a bit of debugging time in cases where the backtrace did not
identify the irq-disabling site well enough.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

CONFIG_DEBUG_LOCKDEP is unacceptably slow because it does not utilize
the chain-hash. Turn the chain-hash back on in this case too.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Cleanup: the VERY_VERBOSE define was unnecessarily dependent on #ifdef VERBOSE
- while the VERBOSE switch is 0 or 1 (always defined).

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Clear all the chains during lockdep_reset().  This fixes some locking-selftest
false positives i saw on -rt.  (never saw those on mainline though, but it
could happen.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Make verbose lockdep messages (off by default) more informative by printing
out the hash chain key.  (this patch was what helped me catch the earlier
lockdep hash-collision bug)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Fix typo in the class_filter() function.  (filtering is not used by default so
this only affects lockdep-internal debugging cases)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

The hash_lock must only ever be taken with irqs disabled.  This happens in
all the important places, except one codepath: register_lock_class().  The
race should trigger rarely because register_lock_class() is quite rare and
single-threaded (happens during init most of the time).

The fix is to disable irqs.

( bug found live in -rt: there preemption is alot more agressive and
  preempting with the hash-lock held caused a lockup.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Remove the no longer used lockdep_internal().

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>