This patch implements the kexec support for ppc64 platforms.

A couple of notes:

1)  We copy the pages in virtual mode, using the full base kernel
    and a statically allocated stack.   At kexec_prepare time we
    scan the pages and if any overlap our (0, _end[]) range we
    return -ETXTBSY.

    On PowerPC 64 systems running in LPAR (logical partitioning)
    mode, only a small region of memory, referred to as the RMO,
    can be accessed in real mode.  Since Linux runs with only one
    zone of memory in the memory allocator, and it can be orders of
    magnitude more memory than the RMO, looping until we allocate
    pages in the source region is not feasible.  Copying in virtual
    means we don't have to write a hash table generation and call
    hypervisor to insert translations, instead we rely on the pinned
    kernel linear mapping.  The kernel already has move to linked
    location built in, so there is no requirement to load it at 0.

    If we want to load something other than a kernel, then a stub
    can be written to copy a linear chunk in real mode.

2)  The start entry point gets passed parameters from the kernel.
    Slaves are started at a fixed address after copying code from
    the entry point.

    All CPUs get passed their firmware assigned physical id in r3
    (most calling conventions use this register for the first
    argument).

    This is used to distinguish each CPU from all other CPUs.
    Since firmware is not around, there is no other way to obtain
    this information other than to pass it somewhere.

    A single CPU, referred to here as the master and the one executing
    the kexec call, branches to start with the address of start in r4.
    While this can be calculated, we have to load it through a gpr to
    branch to this point so defining the register this is contained
    in is free.  A stack of unspecified size is available at r1
    (also common calling convention).

    All remaining running CPUs are sent to start at absolute address
    0x60 after copying the first 0x100 bytes from start to address 0.
    This convention was chosen because it matches what the kernel
    has been doing itself.  (only gpr3 is defined).

    Note: This is not quite the convention of the kexec bootblock v2
    in the kernel.  A stub has been written to convert between them,
    and we may adjust the kernel in the future to allow this directly
    without any stub.

3)  Destination pages can be placed anywhere, even where they
    would not be accessible in real mode.  This will allow us to
    place ram disks above the RMO if we choose.
Signed-off-by: NMilton Miller <miltonm@bga.com>
Signed-off-by: NR Sharada <sharada@in.ibm.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add code to clear the hash table and invalidate the tlb for native (SMP,
non-LPAR) mode.  Supports 16M and 4k pages.
Signed-off-by: NMilton Miller <miltonm@bga.com>
Signed-off-by: NR Sharada <sharada@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I have tweaked this patch slightly to handle an empty list
of pages to relocate passed to relocate_new_kernel.  And
I have added ppc_md.machine_crash_shutdown.  To keep up with
the changes in the generic kexec infrastructure.

From: Albert Herranz <albert_herranz@yahoo.es>

The following patch adds support for kexec on the ppc32 platform.

Non-OpenFirmware based platforms are likely to work directly without
additional changes on the kernel side.  The kexec-tools userland package
may need to be slightly updated, though.

For OpenFirmware based machines, additional work is still needed on the
kernel side before kexec support is ready.  Benjamin Herrenschmidt is
kindly working on that part.

In order for a ppc platform to use the kexec kernel services it must
implement some ppc_md hooks.  Otherwise, kexec will be explicitly disabled,
as suggested by benh.

There are 3+1 new ppc_md hooks that a platform supporting kexec may
implement.  Two of them are mandatory for kexec to work.  See
include/asm-ppc/machdep.h for details.

- machine_kexec_prepare(image)

  This function is called to make any arrangements to the image before it
  is loaded.

  This hook _MUST_ be provided by a platform in order to activate kexec
  support for that platform.  Otherwise, the platform is considered to not
  support kexec and the kexec_load system call will fail (that makes all
  existing platforms by default non-kexec'able).

- machine_kexec_cleanup(image)

  This function is called to make any cleanups on image after the loaded
  image data it is freed.  This hook is optional.  A platform may or may
  not provide this hook.

- machine_kexec(image)

  This function is called to perform the _actual_ kexec.  This hook
  _MUST_ be provided by a platform in order to activate kexec support for
  that platform.

  If a platform provides machine_kexec_prepare but forgets to provide
  machine_kexec, a kexec will fall back to a reboot.

  A ready-to-use machine_kexec_simple() generic function is provided to,
  hopefully, simplify kexec adoption for embedded platforms.  A platform
  may call this function from its specific machine_kexec hook, like this:

void myplatform_kexec(struct kimage *image)
{
        machine_kexec_simple(image);
}

- machine_shutdown()

  This function is called to perform any machine specific shutdowns, not
  already done by drivers.  This hook is optional.  A platform may or may
  not provide this hook.

An example (trimmed) platform specific module for a platform supporting
kexec through the existing machine_kexec_simple follows:

/* ... */

#ifdef CONFIG_KEXEC
int myplatform_kexec_prepare(struct kimage *image)
{
        /* here, we can place additional preparations
*/
        return 0; /* yes, we support kexec */
}

void myplatform_kexec(struct kimage *image)
{
        machine_kexec_simple(image);
}
#endif /* CONFIG_KEXEC */

/* ... */

void __init
platform_init(unsigned long r3, unsigned long r4,
unsigned long r5,
              unsigned long r6, unsigned long r7)
{

/* ... */

#ifdef CONFIG_KEXEC
        ppc_md.machine_kexec_prepare =
myplatform_kexec_prepare;
        ppc_md.machine_kexec         =
myplatform_kexec;
#endif /* CONFIG_KEXEC */

/* ... */

}

The kexec ppc kernel support has been heavily tested on the GameCube Linux
port, and, as reported in the fastboot mailing list, it has been tested too
on a Moto 82xx ppc by Rick Richardson.
Signed-off-by: NAlbert Herranz <albert_herranz@yahoo.es>
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is the x86_64 implementation of the crashkernel option.  It reserves
a window of memory very early in the bootup process, so we never use
it for anything but the kernel to switch to when the running
kernel panics.

In addition to reserving this memory a resource structure is registered
so looking at /proc/iomem it is clear what happened to that memory.

ISSUES:
Is it possible to implement this in a architecture generic way?
What should be done with architectures that always use an iommu and
thus don't report their RAM memory resources in /proc/iomem?
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is the x86_64 implementation of machine kexec.  32bit compatibility
support has been implemented, and machine_kexec has been enhanced to not care
about the changing internal kernel paget table structures.

From: Alexander Nyberg <alexn@dsv.su.se>

      build fix
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Factor out the apic and smp shutdown code from machine_restart so it can be
called by in the kexec reboot path as well.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is the x86 implementation of the crashkernel option.  It reserves a
window of memory very early in the bootup process, so we never use it for
anything but the kernel to switch to when the running kernel panics.

In addition to reserving this memory a resource structure is registered so
looking at /proc/iomem it is clear what happened to that memory.

ISSUES:
Is it possible to implement this in a architecture generic way?
What should be done with architectures that always use an iommu and
thus don't report their RAM memory resources in /proc/iomem?
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

In the case of a crash/panic an architecture specific function
machine_crash_shutdown is called.  This patch adds to the x86 machine_crash
function the standard kernel code for shutting down apics.

Every line of code added to that function increases the risk that we will call
code after a kernel panic that is not safe.

This patch should not make it to the stable kernel without a being reviewed a
lot more.  It is unclear how much a hardned kernel can take when it comes to
misconfigured apics.  So since a normal kernel has problems this patch does a
clean shutdown.

It is my expectation this patch will be dropped from future generations of the
kexec work.  But for the moment it is a crutch to keep from breaking
everything.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

After the kernel panics if we wish to generate an entire machine core file it
is very nice to know the register state at the time the machine crashed.

After long discussion it was realized that if you are going to be saving the
information anyway it is reasonable to store the information in a format that
it will be used and recognized in so the register state is stored in the
standard ELF note format.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

One of the dangers when switching from one kernel to another is what happens
to all of the other cpus that were running in the crashed kernel.  In an
attempt to avoid that problem this patch adds a nmi handler and attempts to
shoot down the other cpus by sending them non maskable interrupts.

The code then waits for 1 second or until all known cpus have stopped running
and then jumps from the running kernel that has crashed to the kernel in
reserved memory.

The kernel spin loop is used for the delay as that should behave continue to
be safe even in after a crash.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is the i386 implementation of kexec.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Factor out the apic and smp shutdown code from machine_restart so it can be
called by in the kexec reboot path as well.

By switching to the bootstrap cpu by default on reboot I can delete/simplify
some motherboard fixups well.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is a minor bug fix in kexec to resolve the problem of loading panic
kernel with initrd.

o Problem: Loading a capture kenrel fails if initrd is also being loaded.
  This has been observed for vmlinux image for kexec on panic case.

o This patch fixes the problem. In segment location and size verification
  logic, minor correction has been done. Segment memory end (mend) should be
  mstart + memsz - 1. This one byte offset was source of failure for initrd
  loading which was being loaded at hole boundary.
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch introduces the architecture independent implementation the
sys_kexec_load, the compat_sys_kexec_load system calls.

Kexec on panic support has been integrated into the core patch and is
relatively clean.

In addition the hopefully architecture independent option
crashkernel=size@location has been docuemented.  It's purpose is to reserve
space for the panic kernel to live, and where no DMA transfer will ever be
setup to access.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAlexander Nyberg <alexn@telia.com>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

For one kernel to report a crash another kernel has created we need
to have 2 kernels loaded simultaneously in memory.  To accomplish this
the two kernels need to built to run at different physical addresses.

This patch adds the CONFIG_PHYSICAL_START option to the x86_64 kernel
so we can do just that.  You need to know what you are doing and
the ramifications are before changing this value, and most users
won't care so I have made it depend on CONFIG_EMBEDDED

bzImage kernels will work and run at a different address when compiled
with this option but they will still load at 1MB.  If you need a kernel
loaded at a different address as well you need to boot a vmlinux.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch fixes a problem with reserving memory during boot up of a kernel
built for non-default location.  Currently boot memory allocator reserves
the memory required by kernel image, boot allocaotor bitmap etc.  It
assumes that kernel is loaded at 1MB (HIGH_MEMORY hard coded to 1024*1024).
 But kernel can be built for non-default locatoin, hence existing
hardcoding will lead to reserving unnecessary memory.  This patch fixes it.
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

For one kernel to report a crash another kernel has created we need
to have 2 kernels loaded simultaneously in memory.  To accomplish this
the two kernels need to built to run at different physical addresses.

This patch adds the CONFIG_PHYSICAL_START option to the x86 kernel
so we can do just that.  You need to know what you are doing and
the ramifications are before changing this value, and most users
won't care so I have made it depend on CONFIG_EMBEDDED

bzImage kernels will work and run at a different address when compiled
with this option but they will still load at 1MB.  If you need a kernel
loaded at a different address as well you need to boot a vmlinux.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The vmlinux on x86_64 does not report the correct physical address of
the kernel.  Instead in the physical address field it currently
reports the virtual address of the kernel.

This is patch is a bug fix that corrects vmlinux to report the
proper physical addresses.

This is potentially a help for crash dump analysis tools.

This definitiely allows bootloaders that load vmlinux as a standard
ELF executable.  Bootloaders directly loading vmlinux become of
practical importance when we consider the kexec on panic case.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The vmlinux on i386 does not report the correct physical address of
the kernel.  Instead in the physical address field it currently
reports the virtual address of the kernel.

This is patch is a bug fix that corrects vmlinux to report the
proper physical addresses.

This is potentially a help for crash dump analysis tools.

This definitiely allows bootloaders that load vmlinux as a standard
ELF executable.  Bootloaders directly loading vmlinux become of
practical importance when we consider the kexec on panic case.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

In vmlinux.lds.h the code is carefull to define every section so vmlinux
properly reports the correct physical load address of code, as well as
it's virtual address.

The new SECURITY_INIT definition fails to follow that convention and
and causes incorrect physical address to appear in the vmlinux if
there are any security initcalls.

This patch updates the SECURITY_INIT to follow the convention in the rest of
the file.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

When coming out of apic mode attempt to set the appropriate
apic back into virtual wire mode.  This improves on previous versions
of this patch by by never setting bot the local apic and the ioapic
into veritual wire mode.

This code looks at data from the mptable to see if an ioapic has
an ExtInt input to make this decision.  A future improvement
is to figure out which apic or ioapic was in virtual wire mode
at boot time and to remember it.  That is potentially a more accurate
method, of selecting which apic to place in virutal wire mode.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

When coming out of apic mode attempt to set the appropriate
apic back into virtual wire mode.  This improves on previous versions
of this patch by by never setting bot the local apic and the ioapic
into veritual wire mode.

This code looks at data from the mptable to see if an ioapic has
an ExtInt input to make this decision.  A future improvement
is to figure out which apic or ioapic was in virtual wire mode
at boot time and to remember it.  That is potentially a more accurate
method, of selecting which apic to place in virutal wire mode.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

From: Eric W. Biederman <ebiederm@xmission.com

The following patch simply adds a shutdown method to the x86_64 i8259 code.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

From: Eric W. Biederman <ebiederm@xmission.com>

This patch disables interrupt generation from the legacy pic on reboot.  Now
that there is a sys_device class it should not be called while drivers are
still using interrupts.

There is a report about this breaking ACPI power off on some systems.
http://bugme.osdl.org/show_bug.cgi?id=4041
However the final comment seems to exonerate this code.  So until
I get more information I believe that was a false positive.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

From: Eric W. Biederman <ebiederm@xmission.com>

It is ok to reserve resources > 4G on x86_64 struct resource is 64bit now :)
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

From: "Maciej W. Rozycki" <macro@linux-mips.org>

Fix a kexec problem whcih causes local APIC detection failure.

The problem is detect_init_APIC() is called early, before the command line
have been processed.  Therefore "lapic" (and "nolapic") have not been seen,
yet.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

From: "Maciej W. Rozycki" <macro@linux-mips.org>

Rename APIC_MODE_EXINT to APIC_MODE_EXTINT - I think it should be named
after what the mode is called in documentation.

From: "Eric W. Biederman" <ebiederm@lnxi.com>

I have reduced this patch to just the name change in the header.  And
integrated the changes into the patches that add those
lines. Otherwise I ran into some ugly dependencies.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch adds a new preemption model: 'Voluntary Kernel Preemption'.  The
3 models can be selected from a new menu:

            (X) No Forced Preemption (Server)
            ( ) Voluntary Kernel Preemption (Desktop)
            ( ) Preemptible Kernel (Low-Latency Desktop)

we still default to the stock (Server) preemption model.

Voluntary preemption works by adding a cond_resched()
(reschedule-if-needed) call to every might_sleep() check.  It is lighter
than CONFIG_PREEMPT - at the cost of not having as tight latencies.  It
represents a different latency/complexity/overhead tradeoff.

It has no runtime impact at all if disabled.  Here are size stats that show
how the various preemption models impact the kernel's size:

    text    data     bss     dec     hex filename
 3618774  547184  179896 4345854  424ffe vmlinux.stock
 3626406  547184  179896 4353486  426dce vmlinux.voluntary   +0.2%
 3748414  548640  179896 4476950  445016 vmlinux.preempt     +3.5%

voluntary-preempt is +0.2% of .text, preempt is +3.5%.

This feature has been tested for many months by lots of people (and it's
also included in the RHEL4 distribution and earlier variants were in Fedora
as well), and it's intended for users and distributions who dont want to
use full-blown CONFIG_PREEMPT for one reason or another.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The only sane way to clean up the current 3 lock_kernel() variants seems to
be to remove the spinlock-based BKL implementations altogether, and to keep
the semaphore-based one only.  If we dont want to do that for whatever
reason then i'm afraid we have to live with the current complexity.  (but
i'm open for other cleanup suggestions as well.)

To explore this possibility we'll (at a minimum) have to know whether the
semaphore-based BKL works fine on plain SMP too.  The patch below enables
this.

The patch may make sense in isolation as well, as it might bring
performance benefits: code that would formerly spin on the BKL spinlock
will now schedule away and give up the CPU.  It might introduce performance
regressions as well, if any performance-critical code uses the BKL heavily
and gets overscheduled due to the semaphore.  I very much hope there is no
such performance-critical codepath left though.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch consolidates the CONFIG_PREEMPT and CONFIG_PREEMPT_BKL
preemption options into kernel/Kconfig.preempt.  This, besides reducing
source-code, also enables more centralized tweaking of preemption related
options.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

ia64 changes similar to kernel/sched.c.
Signed-off-by: NDinakar Guniguntala <dino@in.ibm.com>
Acked-by: NPaul Jackson <pj@sgi.com>
Acked-by: NNick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Adds the core update_cpu_domains code and updated cpusets documentation
Signed-off-by: NDinakar Guniguntala <dino@in.ibm.com>
Acked-by: NPaul Jackson <pj@sgi.com>
Acked-by: NNick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The following patches add dynamic sched domains functionality that was
extensively discussed on lkml and lse-tech.  I would like to see this added to
-mm

o The main advantage with this feature is that it ensures that the scheduler
  load balacing code only balances against the cpus that are in the sched
  domain as defined by an exclusive cpuset and not all of the cpus in the
  system. This removes any overhead due to load balancing code trying to
  pull tasks outside of the cpu exclusive cpuset only to be prevented by
  the tasks' cpus_allowed mask.
o cpu exclusive cpusets are useful for servers running orthogonal
  workloads such as RT applications requiring low latency and HPC
  applications that are throughput sensitive

o It provides a new API partition_sched_domains in sched.c
  that makes dynamic sched domains possible.
o cpu_exclusive cpusets sets are now associated with a sched domain.
  Which means that the users can dynamically modify the sched domains
  through the cpuset file system interface
o ia64 sched domain code has been updated to support this feature as well
o Currently, this does not support hotplug. (However some of my tests
  indicate hotplug+preempt is currently broken)
o I have tested it extensively on x86.
o This should have very minimal impact on performance as none of
  the fast paths are affected
Signed-off-by: NDinakar Guniguntala <dino@in.ibm.com>
Acked-by: NPaul Jackson <pj@sgi.com>
Acked-by: NNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: NMatthew Dobson <colpatch@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Presently, a process without the capability CAP_SYS_NICE can not change
its own policy, which is OK.

But it can also not decrease its RT priority (if scheduled with policy
SCHED_RR or SCHED_FIFO), which is what this patch changes.

The rationale is the same as for the nice value: a process should be
able to require less priority for itself. Increasing the priority is
still not allowed.

This is for example useful if you give a multithreaded user process a RT
priority, and the process would like to organize its internal threads
using priorities also. Then you can give the process the highest
priority needed N, and the process starts its threads with lower
priorities: N-1, N-2...

The POSIX norm says that the permissions are implementation specific, so
I think we can do that.

In a sense, it makes the permissions consistent whatever the policy is:
with this patch, process scheduled by SCHED_FIFO, SCHED_RR and
SCHED_OTHER can all decrease their priority.

From: Ingo Molnar <mingo@elte.hu>

cleaned up and merged to -mm.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

micro-optimize task requeueing in schedule() & clean up recalc_task_prio().
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The maximum rebalance interval allowed by the multiprocessor balancing
backoff is often not large enough to handle corner cases where there are
lots of tasks pinned on a CPU.  Suresh reported:

	I see system livelock's if for example I have 7000 processes
	pinned onto one cpu (this is on the fastest 8-way system I
	have access to).

After this patch, the machine is reported to go well above this number.
Signed-off-by: NNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Consolidate balance-on-exec with balance-on-fork.  This is made easy by the
sched-domains RCU patches.

As well as the general goodness of code reduction, this allows the runqueues
to be unlocked during balance-on-fork.

schedstats is a problem.  Maybe just have balance-on-event instead of
distinguishing fork and exec?
Signed-off-by: NNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

One of the problems with the multilevel balance-on-fork/exec is that it needs
to jump through hoops to satisfy sched-domain's locking semantics (that is,
you may traverse your own domain when not preemptable, and you may traverse
others' domains when holding their runqueue lock).

balance-on-exec had to potentially migrate between more than one CPU before
finding a final CPU to migrate to, and balance-on-fork needed to potentially
take multiple runqueue locks.

So bite the bullet and make sched-domains go completely RCU.  This actually
simplifies the code quite a bit.

From: Ingo Molnar <mingo@elte.hu>

schedstats RCU fix, and a nice comment on for_each_domain, from Ingo.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The fundamental problem that Suresh has with balance on exec and fork is that
it only tries to balance the top level domain with the flag set.

This was worked around by removing degenerate domains, but is still a problem
if people want to start using more complex sched-domains, especially
multilevel NUMA that ia64 is already using.

This patch makes balance on fork and exec try balancing over not just the top
most domain with the flag set, but all the way down the domain tree.
Signed-off-by: NNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Remove degenerate scheduler domains during the sched-domain init.

For example on x86_64, we always have NUMA configured in.  On Intel EM64T
systems, top most sched domain will be of NUMA and with only one sched_group
in it.

With fork/exec balances(recent Nick's fixes in -mm tree), we always endup
taking wrong decisions because of this topmost domain (as it contains only one
group and find_idlest_group always returns NULL).  We will endup loading HT
package completely first, letting active load balance kickin and correct it.

In general, this patch also makes sense with out recent Nick's fixes in -mm.

From: Nick Piggin <nickpiggin@yahoo.com.au>

Modified to account for more than just sched_groups when scanning for
degenerate domains by Nick Piggin.  And allow a runqueue's sd to go NULL
rather than keep a single degenerate domain around (this happens when you run
with maxcpus=1).
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: NNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>