This warning:

[  847.140022] rb_producer   D 0000000000000000  5928   519      2 0x00000000
[  847.203627] BUG: using smp_processor_id() in preemptible [00000000] code: khungtaskd/517
[  847.207360] caller is show_stack_log_lvl+0x2e/0x241
[  847.210364] Pid: 517, comm: khungtaskd Not tainted 2.6.32-rc8-tip+ #13761
[  847.213395] Call Trace:
[  847.215847]  [<ffffffff81413bde>] debug_smp_processor_id+0x1f0/0x20a
[  847.216809]  [<ffffffff81015eae>] show_stack_log_lvl+0x2e/0x241
[  847.220027]  [<ffffffff81018512>] show_stack+0x1c/0x1e
[  847.223365]  [<ffffffff8107b7db>] sched_show_task+0xe4/0xe9
[  847.226694]  [<ffffffff8112f21f>] check_hung_task+0x140/0x199
[  847.230261]  [<ffffffff8112f4a8>] check_hung_uninterruptible_tasks+0x1b7/0x20f
[  847.233371]  [<ffffffff8112f500>] ? watchdog+0x0/0x50
[  847.236683]  [<ffffffff8112f54e>] watchdog+0x4e/0x50
[  847.240034]  [<ffffffff810cee56>] kthread+0x97/0x9f
[  847.243372]  [<ffffffff81012aea>] child_rip+0xa/0x20
[  847.246690]  [<ffffffff81e43494>] ? restore_args+0x0/0x30
[  847.250019]  [<ffffffff81e43083>] ? _spin_lock+0xe/0x10
[  847.253351]  [<ffffffff810cedbf>] ? kthread+0x0/0x9f
[  847.256833]  [<ffffffff81012ae0>] ? child_rip+0x0/0x20

Happens because on preempt-RCU, khungd calls show_stack() with
preemption enabled.

Make sure we are not preemptible while walking the IRQ and exception
stacks on 64-bit. (32-bit stack dumping is preemption safe.)
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Make the initialization more readable, plus tidy up a few small
visual details as well.

No change in functionality.

LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

* remove asm/atomic.h inclusion from linux/utsname.h --
   not needed after kref conversion
 * remove linux/utsname.h inclusion from files which do not need it

NOTE: it looks like fs/binfmt_elf.c do not need utsname.h, however
due to some personality stuff it _is_ needed -- cowardly leave ELF-related
headers and files alone.
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

About every callchains recorded with perf record are filled up
including the internal perfcounter nmi frame:

 perf_callchain
 perf_counter_overflow
 intel_pmu_handle_irq
 perf_counter_nmi_handler
 notifier_call_chain
 atomic_notifier_call_chain
 notify_die
 do_nmi
 nmi

We want ignore this frame as it's not interesting for
instrumentation. To solve this, we simply ignore every frames
from nmi context.

New example of "perf report -s sym -c" after this patch:

9.59%  [k] search_by_key
             4.88%
                search_by_key
                reiserfs_read_locked_inode
                reiserfs_iget
                reiserfs_lookup
                do_lookup
                __link_path_walk
                path_walk
                do_path_lookup
                user_path_at
                vfs_fstatat
                vfs_lstat
                sys_newlstat
                system_call_fastpath
                __lxstat
                0x406fb1

             3.19%
                search_by_key
                search_by_entry_key
                reiserfs_find_entry
                reiserfs_lookup
                do_lookup
                __link_path_walk
                path_walk
                do_path_lookup
                user_path_at
                vfs_fstatat
                vfs_lstat
                sys_newlstat
                system_call_fastpath
                __lxstat
                0x406fb1
[...]

For now this patch only solves the problem in x86-64.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <1246474930-6088-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Signed-off-by: NBrian Gerst <brgerst@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

Move the irqstackptr variable from the PDA to per-cpu.  Make the
stacks themselves per-cpu, removing some specific allocation code.
Add a seperate flag (is_boot_cpu) to simplify the per-cpu boot
adjustments.

tj: * sprinkle some underbars around.

    * irq_stack_ptr is not used till traps_init(), no reason to
      initialize it early.  On SMP, just leaving it NULL till proper
      initialization in setup_per_cpu_areas() works.  Dropped
      is_boot_cpu and early irq_stack_ptr initialization.

    * do DECLARE/DEFINE_PER_CPU(char[IRQ_STACK_SIZE], irq_stack)
      instead of (char, irq_stack[IRQ_STACK_SIZE]).
Signed-off-by: NBrian Gerst <brgerst@gmail.com>
Signed-off-by: NTejun Heo <tj@kernel.org>

Impact: better dumpstack output

I noticed in my crash dumps and even in the stack tracer that a
lot of functions listed in the stack trace are simply
return_to_handler which is ftrace graphs way to insert its own
call into the return of a function.

But we lose out where the actually function was called from.

This patch adds in hooks to the dumpstack mechanism that detects
this and finds the real function to print. Both are printed to
let the user know that a hook is still in place.

This does give a funny side effect in the stack tracer output:

        Depth   Size      Location    (80 entries)
        -----   ----      --------
  0)     4144      48   save_stack_trace+0x2f/0x4d
  1)     4096     128   ftrace_call+0x5/0x2b
  2)     3968      16   mempool_alloc_slab+0x16/0x18
  3)     3952     384   return_to_handler+0x0/0x73
  4)     3568    -240   stack_trace_call+0x11d/0x209
  5)     3808     144   return_to_handler+0x0/0x73
  6)     3664    -128   mempool_alloc+0x4d/0xfe
  7)     3792     128   return_to_handler+0x0/0x73
  8)     3664     -32   scsi_sg_alloc+0x48/0x4a [scsi_mod]

As you can see, the real functions are now negative. This is due
to them not being found inside the stack.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

As promised, now that dumpstack_32 and dumpstack_64 have so many bits
in common, we should merge the in-sync bits into a common file, to
prevent them from diverging again.

This patch removes bits which are common between dumpstack_32.c and
dumpstack_64.c and places them in a common dumpstack.c which is built
for both 32 and 64 bit arches.
Signed-off-by: NNeil Horman <nhorman@tuxdriver.com>
Acked-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

 Makefile       |    2
 arch/x86/kernel/Makefile       |    2
 arch/x86/kernel/Makefile       |    2
 arch/x86/kernel/Makefile       |    2
 arch/x86/kernel/Makefile       |    2
 arch/x86/kernel/Makefile       |    2
 arch/x86/kernel/dumpstack.c    |  319 +++++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/dumpstack.h    |   39 +++++
 arch/x86/kernel/dumpstack_32.c |  294 -------------------------------------
 arch/x86/kernel/dumpstack_64.c |  285 ------------------------------------
 5 files changed, 363 insertions(+), 576 deletions(-)

Make i386's die() equal to x86_64's version.

Whitespace-only changes on x86_64, to make it equal to i386's
version. (user_mode and user_mode_vm are equal on x86_64.)
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Use oops_begin and oops_end in die_nmi.

Whitespace-only changes on x86_64, to make it equal to i386's
version.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Always call oops_exit from oops_end, even if signr==0.

Also, move add_taint(TAINT_DIE) from __die to oops_end
on x86_64 and interchange two lines to make oops_end
more similar to the i386-version.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

oops_end is preceded by either a call to __die, or a conditional
call to crash_kexec. Move the conditional call to crash_kexec
from the end of __die to the start of oops_end and remove
the superfluous call to crash_kexec in die_nmi.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Change oops_end such that signr=0 signals that do_exit
is not to be called.

Currently, each use of __die is soon followed by a call
to oops_end and 'regs' is set to NULL if oops_end is expected
not to call do_exit. Change all such pairs to set signr=0
instead. On x86_64 oops_end is used 'bare' in die_nmi; use
signr=0 instead of regs=NULL there, too.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Print the name of the last-accessed sysfs file when we oops, to help track
down oopses which occur in sysfs store/read handlers.  Because these oopses
tend to not leave any trace of the offending code in the stack traces.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

After "dumpstack: x86: various small unification steps", the
assembler gives the following compile error. The error is in
dumpstack_64.c.

{standard input}: Assembler messages:
{standard input}:720: Error: Incorrect register `%rbx' used with `l' suffix
{standard input}:1340: Error: Incorrect register `%r12' used with `l' suffix

Indeed the suffix in get_bp() was wrong.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

- define STACKSLOTS_PER_LINE and use it
 - define get_bp macro to hide the %%ebp/%%rbp difference
 - i386: check task==NULL in dump_trace, like x86_64
 - i386: show_trace(NULL, ...) uses current automatically
 - x86_64: use [#%d] for die_counter, like i386
 - whitespace and comments
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

- x86: Write log_lvl strings if available
 - start raw stack dumps on new line
 - i386: Remove extra indentation for raw stack dumps
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

- i386 and x86_64: always printk the 'data' parameter
 - i386: announce stack switch (irq -> normal)
 - i386: check if there is a stack switch before announcing it

There is a warning that 'context' might come out corrupt in early
boot. If this is true it should be fixed, not worked around.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

- Add "end" parameter to valid_stack_ptr and print_context_stack
 - use sizeof(long) as the size of a word on the stack
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

- x86_64: use %p to print an address
 - make i386-version the same as the above

The result should be the same on x86_64; on i386 the
output only changes if CONFIG_KALLSYMS is turned off,
in which case the address is printed twice.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The dumpstack code is logically quite independent from the
hardware traps. Split it out into its own file.
Signed-off-by: NAlexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: NIngo Molnar <mingo@elte.hu>