Freezing tasks via the cgroup freezer causes the load average to climb
because the freezer's current implementation puts frozen tasks in
uninterruptible sleep (D state).

Some applications which perform job-scheduling functions consult the
load average when making decisions.  If a cgroup is frozen, the load
average does not provide a useful measure of the system's utilization
to such applications.  This is especially inconvenient if the job
scheduler employs the cgroup freezer as a mechanism for preempting low
priority jobs.  Contrast this with using SIGSTOP for the same purpose:
the stopped tasks do not count toward system load.

Change task_contributes_to_load() to return false if the task is
frozen.  This results in /proc/loadavg behavior that better meets
users' expectations.

Signed-off-by: Nathan Lynch <ntl@pobox.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Nigel Cunningham <nigel@tuxonice.net>
Tested-by: Nigel Cunningham <nigel@tuxonice.net>
Cc: <stable@kernel.org>
Cc: containers@lists.linux-foundation.org
Cc: linux-pm@lists.linux-foundation.org
Cc: Matt Helsley <matthltc@us.ibm.com>
LKML-Reference: <20090408194512.47a99b95@manatee.lan>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

* 'core/softlockup' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  softlockup: make DETECT_HUNG_TASK default depend on DETECT_SOFTLOCKUP
  softlockup: move 'one' to the softlockup section in sysctl.c
  softlockup: ensure the task has been switched out once
  softlockup: remove timestamp checking from hung_task
  softlockup: convert read_lock in hung_task to rcu_read_lock
  softlockup: check all tasks in hung_task
  softlockup: remove unused definition for spawn_softlockup_task
  softlockup: fix potential race in hung_task when resetting timeout
  softlockup: fix to allow compiling with !DETECT_HUNG_TASK
  softlockup: decouple hung tasks check from softlockup detection

Conflicts:
	kernel/sysctl.c

Conflicts:
	include/linux/irq.h
	kernel/irq/handle.c

* 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (413 commits)
  tracing, net: fix net tree and tracing tree merge interaction
  tracing, powerpc: fix powerpc tree and tracing tree interaction
  ring-buffer: do not remove reader page from list on ring buffer free
  function-graph: allow unregistering twice
  trace: make argument 'mem' of trace_seq_putmem() const
  tracing: add missing 'extern' keywords to trace_output.h
  tracing: provide trace_seq_reserve()
  blktrace: print out BLK_TN_MESSAGE properly
  blktrace: extract duplidate code
  blktrace: fix memory leak when freeing struct blk_io_trace
  blktrace: fix blk_probes_ref chaos
  blktrace: make classic output more classic
  blktrace: fix off-by-one bug
  blktrace: fix the original blktrace
  blktrace: fix a race when creating blk_tree_root in debugfs
  blktrace: fix timestamp in binary output
  tracing, Text Edit Lock: cleanup
  tracing: filter fix for TRACE_EVENT_FORMAT events
  ftrace: Using FTRACE_WARN_ON() to check "freed record" in ftrace_release()
  x86: kretprobe-booster interrupt emulation code fix
  ...

Fix up trivial conflicts in
 arch/parisc/include/asm/ftrace.h
 include/linux/memory.h
 kernel/extable.c
 kernel/module.c

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  Remove two unneeded exports and make two symbols static in fs/mpage.c
  Cleanup after commit 585d3bc06f4ca57f975a5a1f698f65a45ea66225
  Trim includes of fdtable.h
  Don't crap into descriptor table in binfmt_som
  Trim includes in binfmt_elf
  Don't mess with descriptor table in load_elf_binary()
  Get rid of indirect include of fs_struct.h
  New helper - current_umask()
  check_unsafe_exec() doesn't care about signal handlers sharing
  New locking/refcounting for fs_struct
  Take fs_struct handling to new file (fs/fs_struct.c)
  Get rid of bumping fs_struct refcount in pivot_root(2)
  Kill unsharing fs_struct in __set_personality()

We are wasting 2 words in signal_struct without any reason to implement
task_pgrp_nr() and task_session_nr().

task_session_nr() has no callers since
2e2ba22ea4fd4bb85f0fa37c521066db6775cbef, we can remove it.

task_pgrp_nr() is still (I believe wrongly) used in fs/autofsX and
fs/coda.

This patch reimplements task_pgrp_nr() via task_pgrp_nr_ns(), and kills
__pgrp/__session and the related helpers.

The change in drivers/char/tty_io.c is cosmetic, but hopefully makes sense
anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Alan Cox <number6@the-village.bc.nu>		[tty parts]
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Inho, the safety rules for vnr/nr_ns helpers are horrible and buggy.

task_pid_nr_ns(task) needs rcu/tasklist depending on task == current.

As for "special" pids, vnr/nr_ns helpers always need rcu.  However, if
task != current, they are unsafe even under rcu lock, we can't trust
task->group_leader without the special checks.

And almost every helper has a callsite which needs a fix.

Also, it is a bit annoying that the implementations of, say,
task_pgrp_vnr() and task_pgrp_nr_ns() are not "symmetrical".

This patch introduces the new helper, __task_pid_nr_ns(), which is always
safe to use, and turns all other helpers into the trivial wrappers.

After this I'll send another patch which converts task_tgid_xxx() as well,
they're are a bit special.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Even if task == current, it is not safe to dereference the result of
task_pgrp/task_session.  We can race with another thread which changes the
special pid via setpgid/setsid.

Document this.  The next 2 patches give an example of the unsafe usage, we
have more bad users.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

By discussion with Roland.

- Rename ptrace_exit() to exit_ptrace(), and change it to do all the
  necessary work with ->ptraced list by its own.

- Move this code from exit.c to ptrace.c

- Update the comment in ptrace_detach() to explain the rechecking of
  the child->ptrace.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Metzger, Markus T" <markus.t.metzger@intel.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>