It is highly desirable to trap into kdb on panic.  The debug core will
attempt to register as the first in line for the panic notifier.

CC: Ingo Molnar <mingo@elte.hu>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

This allows kdb to debug a crash with in the kms code with a
single level recursive re-entry.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

Certain calls from the kdb shell will call out to printk(), and any of
these calls should get vectored back to the kdb_printf() so that the
kdb pager and processing can be used, as well as to properly channel
I/O to the polled I/O devices.

CC: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Acked-by: NAndrew Morton <akpm@linux-foundation.org>

If kdb is open on a serial port that is not actually a console make
sure to call the poll routines to emit and receive characters.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Acked-by: NMartin Hicks <mort@sgi.com>

Some kgdb I/O modules require the ability to create a breakpoint
tasklet, such as kgdboc and external modules such as kgdboe.  The
breakpoint tasklet is used as an asynchronous entry point into the
debugger which will have a different function scope than the current
execution path where it might not be safe to have an inline
breakpoint.  This is true of some of the kgdb I/O drivers which share
code with kgdb and rest of the kernel users.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

The only way the debugger can handle a trap in inside rcu_lock,
notify_die, or atomic_notifier_call_chain without a triple fault is
to have a low level "first opportunity handler" in the int3 exception
handler.

Generally this will be something the vast majority of folks will not
need, but for those who need it, it is added as a kernel .config
option called KGDB_LOW_LEVEL_TRAP.

CC: Ingo Molnar <mingo@elte.hu>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: H. Peter Anvin <hpa@zytor.com>
CC: x86@kernel.org
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

Remove all the references to the kgdb_post_primary_code.  This
function serves no useful purpose because you can obtain the same
information from the "struct kgdb_state *ks" from with in the
debugger, if for some reason you want the data.

Also remove the unintentional duplicate assignment for ks->ex_vector.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

This patch adds in the kdb PS/2 keyboard driver.  This was mostly a
direct port from the original kdb where I cleaned up the code against
checkpatch.pl and added the glue to stitch it into kgdb.

This patch also enables early kdb debug via kgdbwait and the keyboard.

All the access to configure kdb using either a serial console or the
keyboard is done via kgdboc.

If you want to use only the keyboard and want to break in early you
would add to your kernel command arguments:

    kgdboc=kbd kgdbwait

If you wanted serial and or the keyboard access you could use:

    kgdboc=kbd,ttyS0

You can also configure kgdboc as a kernel module or at run time with
the sysfs where you can activate and deactivate kgdb.

Turn it on:
    echo kbd,ttyS0 > /sys/module/kgdboc/parameters/kgdboc

Turn it off:
    echo "" > /sys/module/kgdboc/parameters/kgdboc
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Reviewed-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>

One of the driving forces behind integrating another front end (kdb)
to the debug core is to allow front end commands to be accessible via
gdb's monitor command.  It is true that you could write gdb macros to
get certain data, but you may want to just use gdb to access the
commands that are available in the kdb front end.

This patch implements the Rcmd gdb stub packet.  In gdb you access
this with the "monitor" command.  For instance you could type "monitor
help", "monitor lsmod" or "monitor ps A" etc...

There is no error checking or command restrictions on what you can and
cannot access at this point.  Doing something like trying to set
breakpoints with the monitor command is going to cause nothing but
problems.  Perhaps in the future only the commands that are actually
known to work with the gdb monitor command will be available.
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

The design of the kdb shell requires that every device that can
provide input to kdb have a polling routine that exits immediately if
there is no character available.  This is required in order to get the
page scrolling mechanism working.

Changing the kernel debugger I/O API to require all polling character
routines to exit immediately if there is no data allows the kernel
debugger to process multiple input channels.

NO_POLL_CHAR will be the return code to the polling routine when ever
there is no character available.

CC: linux-serial@vger.kernel.org
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

These are the minimum changes to the kgdb core in order to enable an
API to connect a new front end (kdb) to the debug core.

This patch introduces the dbg_kdb_mode variable controls where the
user level I/O is routed.  It will be routed to the gdbstub (kgdb) or
to the kdb front end which is a simple shell available over the kgdboc
connection.

You can switch back and forth between kdb or the gdb stub mode of
operation dynamically.  From gdb stub mode you can blindly type
"$3#33", or from the kdb mode you can enter "kgdb" to switch to the
gdb stub.

The logic in the debug core depends on kdb to look for the typical gdb
connection sequences and return immediately with KGDB_PASS_EVENT if a
gdb serial command sequence is detected.  That should allow a
reasonably seamless transition between kdb -> gdb without leaving the
kernel exception state.  The two gdb serial queries that kdb is
responsible for detecting are the "?" and "qSupported" packets.

CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Acked-by: NMartin Hicks <mort@sgi.com>

This patch contains the hooks and instrumentation into kernel which
live outside the kernel/debug directory, which the kdb core
will call to run commands like lsmod, dmesg, bt etc...

CC: linux-arch@vger.kernel.org
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Signed-off-by: NMartin Hicks <mort@sgi.com>

This patch contains only the kdb core.  Because the change set was
large, it was split.  The next patch in the series includes the
instrumentation into the core kernel which are mainly helper functions
for kdb.

This work is directly derived from kdb v4.4 found at:

ftp://oss.sgi.com/projects/kdb/download/v4.4/

The kdb internals have been re-organized to make them mostly platform
independent and to connect everything to the debug core which is used by
gdbstub (which has long been known as kgdb).

The original version of kdb was 58,000 lines worth of changes to
support x86.  From that implementation only the kdb shell, and basic
commands for memory access, runcontrol, lsmod, and dmesg where carried
forward.

This is a generic implementation which aims to cover all the current
architectures using the kgdb core: ppc, arm, x86, mips, sparc, sh and
blackfin.  More archictectures can be added by implementing the
architecture specific kgdb functions.

[mort@sgi.com: Compile fix with hugepages enabled]
[mort@sgi.com: Clean breakpoint code renaming kdba_ -> kdb_]
[mort@sgi.com: fix new line after printing registers]
[mort@sgi.com: Remove the concept of global vs. local breakpoints]
[mort@sgi.com: Rework kdb_si_swapinfo to use more generic name]
[mort@sgi.com: fix the information dump macros, remove 'arch' from the names]
[sfr@canb.auug.org.au: include fixup to include linux/slab.h]

CC: linux-arch@vger.kernel.org
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
Signed-off-by: NMartin Hicks <mort@sgi.com>

Split the former kernel/kgdb.c into debug_core.c which contains the
kernel debugger exception logic and to the gdbstub.c which contains
the logic for allowing gdb to talk to the debug core.

This also created a private include file called debug_core.h which
contains all the definitions to glue the debug_core to any other
debugger connections.

CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

Move kgdb.c in preparation to separate the gdbstub from the debug
core and exception handling.

CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

Commit a45185d2 "cpumask: convert kernel/compat.c" broke libnuma, which
abuses sched_getaffinity to find out NR_CPUS in order to parse
/sys/devices/system/node/node*/cpumap.

On NUMA systems with less than 32 possibly CPUs, the current
compat_sys_sched_getaffinity now returns '4' instead of the actual
NR_CPUS/8, which makes libnuma bail out when parsing the cpumap.

The libnuma call sched_getaffinity(0, bitmap, 4096) at first.  It mean
the libnuma expect the return value of sched_getaffinity() is either len
argument or NR_CPUS.  But it doesn't expect to return nr_cpu_ids.

Strictly speaking, userland requirement are

1) Glibc assume the return value mean the lengh of initialized
   of mask argument. E.g. if sched_getaffinity(1024) return 128,
   glibc make zero fill rest 896 byte.
2) Libnuma assume the return value can be used to guess NR_CPUS
   in kernel. It assume len-arg<NR_CPUS makes -EINVAL. But
   it try len=4096 at first and 4096 is always bigger than
   NR_CPUS. Then, if we remove strange min_length normalization,
   we never hit -EINVAL case.

sched_getaffinity() already solved this issue.  This patch adapts
compat_sys_sched_getaffinity() to match the non-compat case.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: NRusty Russell <rusty@rustcorp.com.au>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Reported-by: NKen Werner <ken.werner@web.de>
Cc: stable@kernel.org
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This addresses the following compiler warning:

 kernel/stop_machine.c: In function 'cpu_stop_cpu_callback':
 kernel/stop_machine.c:297: warning: unused variable 'work'

Cc: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <tip-3fc1f1e2@git.kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The exception-trace facility on x86 and other architectures prints
traces to dmesg whenever a user space application crashes.
s390 has such a feature since ages however it is called
userprocess_debug and is enabled differently.
This patch makes sure that whenever one of the two procfs files

/proc/sys/kernel/userprocess_debug
/proc/sys/debug/exception-trace

is modified the contents of the second one changes as well.
That way we keep backwards compatibilty but also support the same
interface like other architectures do.
Besides that the output of the traces is improved since it will now
also contain the corresponding filename of the vma (when available)
where the process caused a fault or trap.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

This update handles a use case where pm_qos update requests need to
silently fail if the update is being sent to a handle that is NULL.

The problem was that the original pm_qos silently fails when a request
update is passed to a parameter that has not been added to the list yet.
This update restores that behavior.
Signed-off-by: Nmarkgross <markgross@thegnar.org>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

If the kernel is large or the profiling step small, /proc/profile
leaks data and readprofile shows silly stats, until readprofile -r
has reset the buffer: clear the prof_buffer when it is vmalloc()ed.
Signed-off-by: NHugh Dickins <hughd@google.com>
Cc: stable@kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When an interrupt is disabled and torn down, the CPU mask returned
through affinity_hint right now is all CPUs. Also, for drivers that
don't provide an affinity_hint mask, this can be misleading. There
should be no hint at all, meaning an empty CPU mask.

[ tglx: use zalloc_cpumask_var instead of clearing it under the lock ]
Signed-off-by: NPeter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Cc: davem@davemloft.net
Cc: arjan@linux.jf.intel.com
Cc: bhutchings@solarflare.com
LKML-Reference: <20100505205638.5426.87189.stgit@ppwaskie-hc2.jf.intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Some callers (in memcontrol.c) calls css_is_ancestor() without
rcu_read_lock.  Because css_is_ancestor() has to access RCU protected
data, it should be under rcu_read_lock().

This makes css_is_ancestor() itself does safe access to RCU protected
area.  (At least, "root" can have refcnt==0 if it's not an ancestor of
"child".  So, we need rcu_read_lock().)
Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit ad4ba375 ("memcg: css_id() must be
called under rcu_read_lock()") modifies memcontol.c for fixing RCU check
message.  But Andrew Morton pointed out that the fix doesn't seems sane
and it was just for hidining lockdep messages.

This is a patch for do proper things.  Checking again, all places,
accessing without rcu_read_lock, that commit fixies was intentional....
all callers of css_id() has reference count on it.  So, it's not necessary
to be under rcu_read_lock().

Considering again, we can use rcu_dereference_check for css_id().  We know
css->id is valid if css->refcnt > 0.  (css->id never changes and freed
after css->refcnt going to be 0.)

This patch makes use of rcu_dereference_check() in css_id/depth and remove
unnecessary rcu-read-lock added by the commit.
Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

acct_exit_ns --> acct_file_reopen deletes timer without check timer
execution on other CPUs.  So acct_timeout() can change an unmapped memory.
Signed-off-by: NVitaliy Gusev <vgusev@openvz.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Two "echo 0 > /sys/kernel/kexec_crash_size" OOPSes kernel.  Also content
of this file is invalid after first shrink to zero: it shows 1 instead of
0.

This scenario is unlikely to happen often (root privs, valid crashkernel=
in cmdline, dump-capture kernel not loaded), I hit it only by chance.

This patch fixes it.
Signed-off-by: NVitaly Mayatskikh <v.mayatskih@gmail.com>
Cc: Cong Wang <amwang@redhat.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Originally, commit d899bf7b ("procfs: provide stack information for
threads") attempted to introduce a new feature for showing where the
threadstack was located and how many pages are being utilized by the
stack.

Commit c44972f1 ("procfs: disable per-task stack usage on NOMMU") was
applied to fix the NO_MMU case.

Commit 89240ba0 ("x86, fs: Fix x86 procfs stack information for threads on
64-bit") was applied to fix a bug in ia32 executables being loaded.

Commit 9ebd4eba ("procfs: fix /proc/<pid>/stat stack pointer for kernel
threads") was applied to fix a bug which had kernel threads printing a
userland stack address.

Commit 1306d603 ('proc: partially revert "procfs: provide stack
information for threads"') was then applied to revert the stack pages
being used to solve a significant performance regression.

This patch nearly undoes the effect of all these patches.

The reason for reverting these is it provides an unusable value in
field 28.  For x86_64, a fork will result in the task->stack_start
value being updated to the current user top of stack and not the stack
start address.  This unpredictability of the stack_start value makes
it worthless.  That includes the intended use of showing how much stack
space a thread has.

Other architectures will get different values.  As an example, ia64
gets 0.  The do_fork() and copy_process() functions appear to treat the
stack_start and stack_size parameters as architecture specific.

I only partially reverted c44972f1 ("procfs: disable per-task stack usage
on NOMMU") .  If I had completely reverted it, I would have had to change
mm/Makefile only build pagewalk.o when CONFIG_PROC_PAGE_MONITOR is
configured.  Since I could not test the builds without significant effort,
I decided to not change mm/Makefile.

I only partially reverted 89240ba0 ("x86, fs: Fix x86 procfs stack
information for threads on 64-bit") .  I left the KSTK_ESP() change in
place as that seemed worthwhile.
Signed-off-by: NRobin Holt <holt@sgi.com>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove all rcu head inits. We don't care about the RCU head state before passing
it to call_rcu() anyway. Only leave the "on_stack" variants so debugobjects can
keep track of objects on stack.
Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

epoll should not touch flags in wait_queue_t. This patch introduces a new
function __add_wait_queue_exclusive(), for the users, who use wait queue as a
LIFO queue.

__add_wait_queue_tail_exclusive() is introduced too instead of
add_wait_queue_exclusive_locked(). remove_wait_queue_locked() is removed, as
it is a duplicate of __remove_wait_queue(), disliked by users, and with less
users.
Signed-off-by: NChangli Gao <xiaosuo@gmail.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: <containers@lists.linux-foundation.org>
LKML-Reference: <1273214006-2979-1-git-send-email-xiaosuo@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Corey reported that the value scale times of group siblings are not
updated when the monitored task dies.

The problem appears to be that we only update the group leader's
time values, fix it by updating the whole group.
Reported-by: NCorey Ashford <cjashfor@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: <stable@kernel.org> # .34.x
LKML-Reference: <1273588935.1810.6.camel@laptop>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Both Stephane and Corey reported that PERF_FORMAT_GROUP didn't
work as expected if the task the counters were attached to quit
before the read() call.

The cause is that we unconditionally destroy the grouping when
we remove counters from their context. Fix this by splitting off
the group destroy from the list removal such that
perf_event_remove_from_context() does not do this and change
perf_event_release() to do so.
Reported-by: NCorey Ashford <cjashfor@linux.vnet.ibm.com>
Reported-by: NStephane Eranian <eranian@google.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: <stable@kernel.org> # .34.x
LKML-Reference: <1273571513.5605.3527.camel@twins>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This reverts commit 4fd38e45.

It causes various crashes and hangs when events are activated.

The cause is not fully understood yet but we need to revert it
because the effects are severe.
Reported-by: NStephane Eranian <eranian@google.com>
Reported-by: NLin Ming <ming.m.lin@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Update stale comments regarding locking order and add a little more detail
so it's easier to follow the locking between the cgroup freezer and the
power management freezer code.
Signed-off-by: NMatt Helsley <matthltc@us.ibm.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

This patch changes the string based list management to a handle base
implementation to help with the hot path use of pm-qos, it also renames
much of the API to use "request" as opposed to "requirement" that was
used in the initial implementation.  I did this because request more
accurately represents what it actually does.

Also, I added a string based ABI for users wanting to use a string
interface.  So if the user writes 0xDDDDDDDD formatted hex it will be
accepted by the interface.  (someone asked me for it and I don't think
it hurts anything.)

This patch updates some documentation input I got from Randy.
Signed-off-by: Nmarkgross <mgross@linux.intel.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Fix printk format warning in block_io.c:

kernel/power/block_io.c:41: warning: format '%ld' expects type 'long int', but argument 2 has type 'sector_t'
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Move all the swap processing into one function. It will make swap
calls from a non-swap code easier.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

The first sector knowledge is swap-only specific. Move it into the
swap handle. This will be needed for later non-swap specific code
moving into snapshot.c.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: N"Rafael J. Wysocki" <rjw@sisk.pl>

Move block I/O operations to a separate file. It is because it will
be used later not only by the swap writer.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Remove support of reads with offset. This means snapshot_read/write_next
now does not accept count parameter. It allows to clean up the functions
and snapshot handle which no longer needs to care about offsets.

/dev/snapshot handler is converted to simple_{read_from,write_to}_buffer
which take care of offsets.
Signed-off-by: NJiri Slaby <jslaby@suse.cz>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

The current version of RCU_FAST_NO_HZ reproduces the old CLASSIC_RCU
dyntick-idle bug, as it fails to detect CPUs that have interrupted
or NMIed out of dyntick-idle mode.  Fix this by making rcu_needs_cpu()
check the state in the per-CPU rcu_dynticks variables, thus correctly
detecting the dyntick-idle state from an RCU perspective.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>