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  1. 30 1月, 2008 10 次提交
  3. 15 1月, 2008 1 次提交
    • S
      Kick CPUS that might be sleeping in cpus_idle_wait · 40d6a146
      由 Steven Rostedt 提交于 
      Sometimes cpu_idle_wait gets stuck because it might miss CPUS that are
already in idle, have no tasks waiting to run and have no interrupts going
to them.  This is common on bootup when switching cpu idle governors.

This patch gives those CPUS that don't check in an IPI kick.

 Background:
 -----------
I notice this while developing the mcount patches, that every once in a
while the system would hang. Looking deeper, the hang was always at boot
up when registering init_menu of the cpu_idle menu governor. Talking
with Thomas Gliexner, we discovered that one of the CPUS had no timer
events scheduled for it and it was in idle (running with NO_HZ). So the
CPU would not set the cpu_idle_state bit.

Hitting sysrq-t a few times would eventually route the interrupt to the
stuck CPU and the system would continue.

Note, I would have used the PDA isidle but that is set after the
cpu_idle_state bit is cleared, and would leave a window open where we
may miss being kicked.

hmm, looking closer at this, we still have a small race window between
clearing the cpu_idle_state and disabling interrupts (hence the RFC).

    CPU0:                          CPU 1:
  ---------                       ---------
 cpu_idle_wait():                 cpu_idle():
      |                           __cpu_cpu_var(is_idle) = 1;
      |                           if (__get_cpu_var(cpu_idle_state)) /* == 0 */
 per_cpu(cpu_idle_state, 1) = 1;         |
 if (per_cpu(is_idle, 1)) /* == 1 */     |
 smp_call_function(1)                    |
      |                             receives ipi and runs do_nothing.
 wait on map == empty               idle();
   /* waits forever */

So really we need interrupts off for most of this then. One might think
that we could simply clear the cpu_idle_state from do_nothing, but I'm
assuming that cpu_idle governors can be removed, and this might cause a
race that a governor might be used after the module was removed.

Venki said:

  I think your RFC patch is the right solution here.  As I see it, there is
  no race with your RFC patch.  As long as you call a dummy smp_call_function
  on all CPUs, we should be OK.  We can get rid of cpu_idle_state and the
  current wait forever logic altogether with dummy smp_call_function.  And so
  there wont be any wait forever scenario.

  The whole point of cpu_idle_wait() is to make all CPUs come out of idle
  loop atleast once.  The caller will use cpu_idle_wait something like this.

  // Want to change idle handler

  - Switch global idle handler to always present default_idle

  - call cpu_idle_wait so that all cpus come out of idle for an instant
    and stop using old idle pointer and start using default idle

  - Change the idle handler to a new handler

  - optional cpu_idle_wait if you want all cpus to start using the new
    handler immediately.

Maybe the below 1s patch is safe bet for .24.  But for .25, I would say we
just replace all complicated logic by simple dummy smp_call_function and
remove cpu_idle_state altogether.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      40d6a146
  5. 17 10月, 2007 1 次提交
  7. 14 10月, 2007 1 次提交
    • D
      Delete filenames in comments. · 835c34a1
      由 Dave Jones 提交于 
      Since the x86 merge, lots of files that referenced their own filenames
are no longer correct.  Rather than keep them up to date, just delete
them, as they add no real value.

Additionally:
- fix up comment formatting in scx200_32.c
- Remove a credit from myself in setup_64.c from a time when we had no SCM
- remove longwinded history from tsc_32.c which can be figured out from
  git.
Signed-off-by: NDave Jones <davej@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      835c34a1
  9. 13 10月, 2007 1 次提交
  11. 11 10月, 2007 2 次提交
  13. 22 9月, 2007 1 次提交
  15. 30 7月, 2007 1 次提交
    • A
      Remove fs.h from mm.h · 4e950f6f
      由 Alexey Dobriyan 提交于 
      Remove fs.h from mm.h. For this,
 1) Uninline vma_wants_writenotify(). It's pretty huge anyway.
 2) Add back fs.h or less bloated headers (err.h) to files that need it.

As result, on x86_64 allyesconfig, fs.h dependencies cut down from 3929 files
rebuilt down to 3444 (-12.3%).

Cross-compile tested without regressions on my two usual configs and (sigh):

alpha              arm-mx1ads        mips-bigsur          powerpc-ebony
alpha-allnoconfig  arm-neponset      mips-capcella        powerpc-g5
alpha-defconfig    arm-netwinder     mips-cobalt          powerpc-holly
alpha-up           arm-netx          mips-db1000          powerpc-iseries
arm                arm-ns9xxx        mips-db1100          powerpc-linkstation
arm-assabet        arm-omap_h2_1610  mips-db1200          powerpc-lite5200
arm-at91rm9200dk   arm-onearm        mips-db1500          powerpc-maple
arm-at91rm9200ek   arm-picotux200    mips-db1550          powerpc-mpc7448_hpc2
arm-at91sam9260ek  arm-pleb          mips-ddb5477         powerpc-mpc8272_ads
arm-at91sam9261ek  arm-pnx4008       mips-decstation      powerpc-mpc8313_rdb
arm-at91sam9263ek  arm-pxa255-idp    mips-e55             powerpc-mpc832x_mds
arm-at91sam9rlek   arm-realview      mips-emma2rh         powerpc-mpc832x_rdb
arm-ateb9200       arm-realview-smp  mips-excite          powerpc-mpc834x_itx
arm-badge4         arm-rpc           mips-fulong          powerpc-mpc834x_itxgp
arm-carmeva        arm-s3c2410       mips-ip22            powerpc-mpc834x_mds
arm-cerfcube       arm-shannon       mips-ip27            powerpc-mpc836x_mds
arm-clps7500       arm-shark         mips-ip32            powerpc-mpc8540_ads
arm-collie         arm-simpad        mips-jazz            powerpc-mpc8544_ds
arm-corgi          arm-spitz         mips-jmr3927         powerpc-mpc8560_ads
arm-csb337         arm-trizeps4      mips-malta           powerpc-mpc8568mds
arm-csb637         arm-versatile     mips-mipssim         powerpc-mpc85xx_cds
arm-ebsa110        i386              mips-mpc30x          powerpc-mpc8641_hpcn
arm-edb7211        i386-allnoconfig  mips-msp71xx         powerpc-mpc866_ads
arm-em_x270        i386-defconfig    mips-ocelot          powerpc-mpc885_ads
arm-ep93xx         i386-up           mips-pb1100          powerpc-pasemi
arm-footbridge     ia64              mips-pb1500          powerpc-pmac32
arm-fortunet       ia64-allnoconfig  mips-pb1550          powerpc-ppc64
arm-h3600          ia64-bigsur       mips-pnx8550-jbs     powerpc-prpmc2800
arm-h7201          ia64-defconfig    mips-pnx8550-stb810  powerpc-ps3
arm-h7202          ia64-gensparse    mips-qemu            powerpc-pseries
arm-hackkit        ia64-sim          mips-rbhma4200       powerpc-up
arm-integrator     ia64-sn2          mips-rbhma4500       s390
arm-iop13xx        ia64-tiger        mips-rm200           s390-allnoconfig
arm-iop32x         ia64-up           mips-sb1250-swarm    s390-defconfig
arm-iop33x         ia64-zx1          mips-sead            s390-up
arm-ixp2000        m68k              mips-tb0219          sparc
arm-ixp23xx        m68k-amiga        mips-tb0226          sparc-allnoconfig
arm-ixp4xx         m68k-apollo       mips-tb0287          sparc-defconfig
arm-jornada720     m68k-atari        mips-workpad         sparc-up
arm-kafa           m68k-bvme6000     mips-wrppmc          sparc64
arm-kb9202         m68k-hp300        mips-yosemite        sparc64-allnoconfig
arm-ks8695         m68k-mac          parisc               sparc64-defconfig
arm-lart           m68k-mvme147      parisc-allnoconfig   sparc64-up
arm-lpd270         m68k-mvme16x      parisc-defconfig     um-x86_64
arm-lpd7a400       m68k-q40          parisc-up            x86_64
arm-lpd7a404       m68k-sun3         powerpc              x86_64-allnoconfig
arm-lubbock        m68k-sun3x        powerpc-cell         x86_64-defconfig
arm-lusl7200       mips              powerpc-celleb       x86_64-up
arm-mainstone      mips-atlas        powerpc-chrp32
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4e950f6f
  17. 23 7月, 2007 1 次提交
  19. 22 7月, 2007 3 次提交
  21. 09 5月, 2007 1 次提交
    • C
      move die notifier handling to common code · 1eeb66a1
      由 Christoph Hellwig 提交于 
      This patch moves the die notifier handling to common code.  Previous
various architectures had exactly the same code for it.  Note that the new
code is compiled unconditionally, this should be understood as an appel to
the other architecture maintainer to implement support for it aswell (aka
sprinkling a notify_die or two in the proper place)

arm had a notifiy_die that did something totally different, I renamed it to
arm_notify_die as part of the patch and made it static to the file it's
declared and used at.  avr32 used to pass slightly less information through
this interface and I brought it into line with the other architectures.

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: fix vmalloc_sync_all bustage]
[bryan.wu@analog.com: fix vmalloc_sync_all in nommu]
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Cc: <linux-arch@vger.kernel.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: NBryan Wu <bryan.wu@analog.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1eeb66a1
  23. 03 5月, 2007 1 次提交
  25. 19 3月, 2007 1 次提交
  27. 23 12月, 2006 1 次提交
    • I
      [PATCH] sched: fix bad missed wakeups in the i386, x86_64, ia64, ACPI and APM idle code · 0888f06a
      由 Ingo Molnar 提交于 
      Fernando Lopez-Lezcano reported frequent scheduling latencies and audio
xruns starting at the 2.6.18-rt kernel, and those problems persisted all
until current -rt kernels. The latencies were serious and unjustified by
system load, often in the milliseconds range.

After a patient and heroic multi-month effort of Fernando, where he
tested dozens of kernels, tried various configs, boot options,
test-patches of mine and provided latency traces of those incidents, the
following 'smoking gun' trace was captured by him:

                 _------=> CPU#
                / _-----=> irqs-off
               | / _----=> need-resched
               || / _---=> hardirq/softirq
               ||| / _--=> preempt-depth
               |||| /
               |||||     delay
   cmd     pid ||||| time  |   caller
      \   /    |||||   \   |   /
  IRQ_19-1479  1D..1    0us : __trace_start_sched_wakeup (try_to_wake_up)
  IRQ_19-1479  1D..1    0us : __trace_start_sched_wakeup <<...>-5856> (37 0)
  IRQ_19-1479  1D..1    0us : __trace_start_sched_wakeup (c01262ba 0 0)
  IRQ_19-1479  1D..1    0us : resched_task (try_to_wake_up)
  IRQ_19-1479  1D..1    0us : __spin_unlock_irqrestore (try_to_wake_up)
  ...
  <idle>-0     1...1   11us!: default_idle (cpu_idle)
  ...
  <idle>-0     0Dn.1  602us : smp_apic_timer_interrupt (c0103baf 1 0)
  ...
   <...>-5856  0D..2  618us : __switch_to (__schedule)
   <...>-5856  0D..2  618us : __schedule <<idle>-0> (20 162)
   <...>-5856  0D..2  619us : __spin_unlock_irq (__schedule)
   <...>-5856  0...1  619us : trace_stop_sched_switched (__schedule)
   <...>-5856  0D..1  619us : trace_stop_sched_switched <<...>-5856> (37 0)

what is visible in this trace is that CPU#1 ran try_to_wake_up() for
PID:5856, it placed PID:5856 on CPU#0's runqueue and ran resched_task()
for CPU#0. But it decided to not send an IPI that no CPU - due to
TS_POLLING. But CPU#0 never woke up after its NEED_RESCHED bit was set,
and only rescheduled to PID:5856 upon the next lapic timer IRQ. The
result was a 600+ usecs latency and a missed wakeup!

the bug turned out to be an idle-wakeup bug introduced into the mainline
kernel this summer via an optimization in the x86_64 tree:

    commit 495ab9c0
    Author: Andi Kleen <ak@suse.de>
    Date:   Mon Jun 26 13:59:11 2006 +0200

    [PATCH] i386/x86-64/ia64: Move polling flag into thread_info_status

    During some profiling I noticed that default_idle causes a lot of
    memory traffic. I think that is caused by the atomic operations
    to clear/set the polling flag in thread_info. There is actually
    no reason to make this atomic - only the idle thread does it
    to itself, other CPUs only read it. So I moved it into ti->status.

the problem is this type of change:

        if (!hlt_counter && boot_cpu_data.hlt_works_ok) {
-               clear_thread_flag(TIF_POLLING_NRFLAG);
+               current_thread_info()->status &= ~TS_POLLING;
                smp_mb__after_clear_bit();
                while (!need_resched()) {
                        local_irq_disable();

this changes clear_thread_flag() to an explicit clearing of TS_POLLING.
clear_thread_flag() is defined as:

        clear_bit(flag, &ti->flags);

and clear_bit() is a LOCK-ed atomic instruction on all x86 platforms:

  static inline void clear_bit(int nr, volatile unsigned long * addr)
  {
          __asm__ __volatile__( LOCK_PREFIX
                  "btrl %1,%0"

hence smp_mb__after_clear_bit() is defined as a simple compile barrier:

  #define smp_mb__after_clear_bit()       barrier()

but the explicit TS_POLLING clearing introduced by the patch:

+               current_thread_info()->status &= ~TS_POLLING;

is not an atomic op! So the clearing of the TS_POLLING bit is freely
reorderable with the reading of the NEED_RESCHED bit - and both now
reside in different memory addresses.

CPU idle wakeup very much depends on ordered memory ops, the clearing of
the TS_POLLING flag must always be done before we test need_resched()
and hit the idle instruction(s). [Symmetrically, the wakeup code needs
to set NEED_RESCHED before it tests the TS_POLLING flag, so memory
ordering is paramount.]

Fernando's dual-core Athlon64 system has a sufficiently advanced memory
ordering model so that it triggered this scenario very often.

( And it also turned out that the reason why these latencies never
  triggered on my testsystems is that i routinely use idle=poll, which
  was the only idle variant not affected by this bug. )

The fix is to change the smp_mb__after_clear_bit() to an smp_mb(), to
act as an absolute barrier between the TS_POLLING write and the
NEED_RESCHED read. This affects almost all idling methods (default,
ACPI, APM), on all 3 x86 architectures: i386, x86_64, ia64.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Tested-by: NFernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      0888f06a
  29. 07 12月, 2006 2 次提交
    • V
      [PATCH] x86-64: Fix interrupt race in idle callback (3rd try) · d331e739
      由 Venkatesh Pallipadi 提交于 
      Idle callbacks has some races when enter_idle() sets isidle and subsequent
interrupts that can happen on that CPU, before CPU goes to idle. Due to this,
an IDLE_END can get called before IDLE_START. To avoid these races, disable
interrupts before enter_idle and make sure that all idle routines do not
enable interrupts before entering idle.

Note that poll_idle() still has a this race as it has to enable interrupts
before going to idle. But, all other idle routines have the race fixed.
Signed-off-by: NVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
      d331e739
    • A
      [PATCH] x86: Don't use nested idle loops · 72690a21
      由 Andi Kleen 提交于 
      Currently the idle loop has two nested loops -- one high level
in cpu_idle and in some low level idle functions another one.

Looping in the low level idle functions breaks the idle notifiers
because interrupts waking up sleep states need to execute
exit_idle() which is only in cpu_idle().

So don't do that, only loop in cpu_idle(). This only removes
code.

In some cases e.g. poll_idle the idle loop is a little longer
now because cpu_idle checks more things. I hope that isn't a problem
ACPI idle doesn't change behaviour because it never looped anyways.

Cc: len.brown@intel.com
Cc: eranian@hpl.hp.com
Signed-off-by: NAndi Kleen <ak@suse.de>
      72690a21
  31. 18 11月, 2006 1 次提交
    • I
      [PATCH] i386/x86_64: ACPI cpu_idle_wait() fix · dc1829a4
      由 Ingo Molnar 提交于 
      The scheduler on Andreas Friedrich's hyperthreading system stopped
working properly: the scheduler would never move tasks to another CPU!
The lask known working kernel was 2.6.8.

After a couple of attempts to corner the bug, the following smoking gun
was found:

  BIOS reported wrong ACPI idfor the processor
  CPU#1: set_cpus_allowed(), swapper:1, 3 -> 2
   [<c0103bbe>] show_trace_log_lvl+0x34/0x4a
   [<c0103ceb>] show_trace+0x2c/0x2e
   [<c01045f8>] dump_stack+0x2b/0x2d
   [<c0116a77>] set_cpus_allowed+0x52/0xec
   [<c0101d86>] cpu_idle_wait+0x2e/0x100
   [<c0259c57>] acpi_processor_power_exit+0x45/0x58
   [<c0259752>] acpi_processor_remove+0x46/0xea
   [<c025c6fb>] acpi_start_single_object+0x47/0x54
   [<c025cee5>] acpi_bus_register_driver+0xa4/0xd3
   [<c04ab2d7>] acpi_processor_init+0x57/0x77
   [<c01004d7>] init+0x146/0x2fd
   [<c0103a87>] kernel_thread_helper+0x7/0x10

a quick look at cpu_idle_wait() shows how broken that code is
on i386: it changes the init task's affinity map but never
restores it ...

and because all userspace tasks get forked by init, they all
inherited that single-CPU affinity mask. x86_64 cloned this
bug too.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Cc: Andreas Friedrich <andreas.friedrich@fujitsu-siemens.com>
Cc: Wolfgang Erig <Wolfgang.Erig@fujitsu-siemens.com>
Cc: Andrew Morton <akpm@osdl.org>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      dc1829a4
  33. 14 11月, 2006 1 次提交
    • A
      [PATCH] x86-64: Fix race in exit_idle · 9446868b
      由 Andi Kleen 提交于 
      When another interrupt happens in exit_idle the exit idle notifier
could be called an incorrect number of times.

Add a test_and_clear_bit_pda and use it handle the bit
atomically against interrupts to avoid this.

Pointed out by Stephane Eranian
Signed-off-by: NAndi Kleen <ak@suse.de>
      9446868b
  35. 14 10月, 2006 1 次提交
  37. 06 10月, 2006 1 次提交
    • A
      [PATCH] x86-64: Fix FPU corruption · 0a5ace2a
      由 Andi Kleen 提交于 
      This reverts an earlier patch that was found to cause FPU
state corruption. I think the corruption happens because
unlazy_fpu() can cause FPU exceptions and when it happens
after the current switch some processing would affect
the state in the wrong process.

Thanks to  Douglas Crosher and Tom Hughes for testing.

Cc: jbeulich@novell.com
Signed-off-by: NAndi Kleen <ak@suse.de>
      0a5ace2a
  39. 02 10月, 2006 1 次提交
    • S
      [PATCH] namespaces: utsname: use init_utsname when appropriate · 96b644bd
      由 Serge E. Hallyn 提交于 
      In some places, particularly drivers and __init code, the init utsns is the
appropriate one to use.  This patch replaces those with a the init_utsname
helper.

Changes: Removed several uses of init_utsname().  Hope I picked all the
	right ones in net/ipv4/ipconfig.c.  These are now changed to
	utsname() (the per-process namespace utsname) in the previous
	patch (2/7)

[akpm@osdl.org: CIFS fix]
Signed-off-by: NSerge E. Hallyn <serue@us.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Andrey Savochkin <saw@sw.ru>
Cc: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      96b644bd
  41. 26 9月, 2006 6 次提交
    • A
      [PATCH] Fix idle notifiers · a15da49d
      由 Andi Kleen 提交于 
      Previously exit_idle would be called more often than enter_idle

Now instead of using complicated tests just keep track of it
using the per CPU variable as a flip flop.  I moved the idle state into the
PDA to make the access more efficient.

Original bug report and an initial patch from Stephane Eranian,
but redone by AK.

Cc: Stephane Eranian <eranian@hpl.hp.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
      a15da49d
    • A
      [PATCH] Fix a PDA warning uncovered by the new type checking · 7b0bda74
      由 Andi Kleen 提交于 
      Fix
linux/arch/x86_64/kernel/process.c: In function __switch_to:
linux/arch/x86_64/kernel/process.c:626: warning: assignment makes integer from pointer without a cast
Signed-off-by: NAndi Kleen <ak@suse.de>
      7b0bda74
    • A
      [PATCH] Add the canary field to the PDA area and the task struct · 0a425405
      由 Arjan van de Ven 提交于 
      This patch adds the per thread cookie field to the task struct and the PDA.
Also it makes sure that the PDA value gets the new cookie value at context
switch, and that a new task gets a new cookie at task creation time.
Signed-off-by: NArjan van Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndi Kleen <ak@suse.de>
CC: Andi Kleen <ak@suse.de>
      0a425405
    • A
      [PATCH] non lazy "sleazy" fpu implementation · e07e23e1
      由 Arjan van de Ven 提交于 
      Right now the kernel on x86-64 has a 100% lazy fpu behavior: after *every*
context switch a trap is taken for the first FPU use to restore the FPU
context lazily.  This is of course great for applications that have very
sporadic or no FPU use (since then you avoid doing the expensive
save/restore all the time).  However for very frequent FPU users...  you
take an extra trap every context switch.

The patch below adds a simple heuristic to this code: After 5 consecutive
context switches of FPU use, the lazy behavior is disabled and the context
gets restored every context switch.  If the app indeed uses the FPU, the
trap is avoided.  (the chance of the 6th time slice using FPU after the
previous 5 having done so are quite high obviously).

After 256 switches, this is reset and lazy behavior is returned (until
there are 5 consecutive ones again).  The reason for this is to give apps
that do longer bursts of FPU use still the lazy behavior back after some
time.

[akpm@osdl.org: place new task_struct field next to jit_keyring to save space]
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
      e07e23e1
    • A
      [PATCH] i386/x86-64: Don't randomize stack top when no randomization personality is set · c16b63e0
      由 Andi Kleen 提交于 
      Based on patch from Frank van Maarseveen <frankvm@frankvm.com>, but
extended.
Signed-off-by: NAndi Kleen <ak@suse.de>
      c16b63e0
    • S
      [PATCH] x86-64 TIF flags for debug regs and io bitmap in ctxsw · d3a4f48d
      由 Stephane Eranian 提交于 
      Hello,

Following my discussion with Andi. Here is a patch that introduces
two new TIF flags to simplify the context switch code in __switch_to().
The idea is to minimize the number of cache lines accessed in the common
case, i.e., when neither the debug registers nor the I/O bitmap are used.

This patch covers the x86-64 modifications. A patch for i386 follows.

Changelog:
	- add TIF_DEBUG to track when debug registers are active
	- add TIF_IO_BITMAP to track when I/O bitmap is used
	- modify __switch_to() to use the new TIF flags

<signed-off-by>: eranian@hpl.hp.com
Signed-off-by: NAndi Kleen <ak@suse.de>
      d3a4f48d
  43. 04 7月, 2006 1 次提交