Commit Graph

1612 Commits

Author SHA1 Message Date
Linus Torvalds
fb5131e188 Merge branch 'for-linus' of git://git390.marist.edu/pub/scm/linux-2.6
* 'for-linus' of git://git390.marist.edu/pub/scm/linux-2.6: (65 commits)
  [S390] prevent unneccesary loops_per_jiffy recalculation
  [S390] cpuinfo: use get_online_cpus() instead of preempt_disable()
  [S390] smp: remove cpu hotplug messages
  [S390] mutex: enable spinning mutex on s390
  [S390] mutex: Introduce arch_mutex_cpu_relax()
  [S390] cio: fix ccwgroup unregistration race condition
  [S390] perf: add DWARF register lookup for s390
  [S390] cleanup ftrace backend functions
  [S390] ptrace cleanup
  [S390] smp/idle: call init_idle() before starting a new cpu
  [S390] smp: delay idle task creation
  [S390] dasd: Correct retry counter for terminated I/O.
  [S390] dasd: Add support for raw ECKD access.
  [S390] dasd: Prevent deadlock during suspend/resume.
  [S390] dasd: Improve handling of stolen DASD reservation
  [S390] dasd: do path verification for paths added at runtime
  [S390] dasd: add High Performance FICON multitrack support
  [S390] cio: reduce memory consumption of itcw structures
  [S390] nmi: enable machine checks early
  [S390] qeth: buffer count imbalance
  ...
2011-01-07 14:50:50 -08:00
Linus Torvalds
abb359450f Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6: (1436 commits)
  cassini: Use local-mac-address prom property for Cassini MAC address
  net: remove the duplicate #ifdef __KERNEL__
  net: bridge: check the length of skb after nf_bridge_maybe_copy_header()
  netconsole: clarify stopping message
  netconsole: don't announce stopping if nothing happened
  cnic: Fix the type field in SPQ messages
  netfilter: fix export secctx error handling
  netfilter: fix the race when initializing nf_ct_expect_hash_rnd
  ipv4: IP defragmentation must be ECN aware
  net: r6040: Return proper error for r6040_init_one
  dcb: use after free in dcb_flushapp()
  dcb: unlock on error in dcbnl_ieee_get()
  net: ixp4xx_eth: Return proper error for eth_init_one
  include/linux/if_ether.h: Add #define ETH_P_LINK_CTL for HPNA and wlan local tunnel
  net: add POLLPRI to sock_def_readable()
  af_unix: Avoid socket->sk NULL OOPS in stream connect security hooks.
  net_sched: pfifo_head_drop problem
  mac80211: remove stray extern
  mac80211: implement off-channel TX using hw r-o-c offload
  mac80211: implement hardware offload for remain-on-channel
  ...
2011-01-06 12:30:19 -08:00
Heiko Carstens
8e1023016c [S390] prevent unneccesary loops_per_jiffy recalculation
When the seqfile /proc/cpuinfo gets accesses for each possible cpu
loops_per_jiffy gets recalculated. However its value is only needed
on first access.
In addition loops_per_jiffy should be recalculated when the machine
reports a capability change.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:32 +01:00
Heiko Carstens
19726cec63 [S390] cpuinfo: use get_online_cpus() instead of preempt_disable()
Use get_online_cpus() instead of preempt_disable() to make sure cpus
don't go offline while accessing their per cpu data.
The preempt_disable() stuff is old code which was used before
get_online_cpus() was available.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:31 +01:00
Heiko Carstens
974de4d7e7 [S390] smp: remove cpu hotplug messages
Get rid of messages that indicate if a cpu went online or offline.
There is nothing special about this anymore and these messages might
flood the kernel log buffer which makes debugging harder since more
important messages might be overwritten.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:31 +01:00
Gerald Schaefer
fa188ae165 [S390] mutex: enable spinning mutex on s390
This enables the spinning mutex feature on s390 by removing
HAVE_DEFAULT_NO_SPIN_MUTEXES from arch/s390/Kconfig.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:31 +01:00
Gerald Schaefer
34b133f8e9 [S390] mutex: Introduce arch_mutex_cpu_relax()
The spinning mutex implementation uses cpu_relax() in busy loops as a
compiler barrier. Depending on the architecture, cpu_relax() may do more
than needed in this specific mutex spin loops. On System z we also give
up the time slice of the virtual cpu in cpu_relax(), which prevents
effective spinning on the mutex.

This patch replaces cpu_relax() in the spinning mutex code with
arch_mutex_cpu_relax(), which can be defined by each architecture that
selects HAVE_ARCH_MUTEX_CPU_RELAX. The default is still cpu_relax(), so
this patch should not affect other architectures than System z for now.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1290437256.7455.4.camel@thinkpad>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-01-05 12:47:31 +01:00
Martin Schwidefsky
4cc9bed034 [S390] cleanup ftrace backend functions
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:31 +01:00
Martin Schwidefsky
5e9a26928f [S390] ptrace cleanup
Overhaul program event recording and the code dealing with the ptrace
user space interface.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:31 +01:00
Heiko Carstens
da7f51c11d [S390] smp/idle: call init_idle() before starting a new cpu
Call init_idle() which (re-)initializes the idle task structure before
it gets used on a new cpu.
That way we can also get rid of the odd preempt_enable_no_resched()
call we have in the cpu offline path within cpu_idle(). That call
prevented preempt count imbalances between cpu hotplug operations.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:30 +01:00
Heiko Carstens
f230886b0b [S390] smp: delay idle task creation
Delay idle task creation until a cpu gets set online instead of
creating them for all possible cpus at system startup.
For one cpu system this should safe more than 1 MB.
On my debug system with lots of debug stuff enabled this saves 2 MB.

Same as on x86.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:30 +01:00
Stefan Haberland
e4dbb0f2b5 [S390] dasd: Add support for raw ECKD access.
Normal I/O operations through the DASD device driver give only access
to the data fields of an ECKD device even for track based I/O.
This patch extends the DASD device driver to give access to whole
ECKD tracks including count, key and data fields.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:30 +01:00
Stefan Weinhuber
5a27e60dec [S390] dasd: Improve handling of stolen DASD reservation
If a DASD device has been reserved by a Linux system, and later
this reservation is ‘stolen’ by a second system by means of an
unconditional reserve, then the first system receives a
notification about this fact. With this patch such an event can
be either ignored, as before, or it can be used to let the device
fail all I/O request, so that the device will not block anymore.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:30 +01:00
Heiko Carstens
f3e1a27359 [S390] nmi: enable machine checks early
Until now machine checks for the swapper process of the IPL cpu are just
implicitly (and more or less accidently) enabled when the first time the
idle process goes into idle state and loads an enabled wait psw.
Before that machine checks are disabled.
So let's enable them explicitly in trap_init() so we have a well defined
time when machine checks are enabled.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:29 +01:00
Martin Schwidefsky
1de3447a41 [S390] 31 bit entry.S update.
Make the code in the 31 bit entry.S code as similar as possible to the
64 bit version in entry64.S. That makes it easier to add new code to
the first level interrupt handler that affects both 31 and 64 bit kernels.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:29 +01:00
Sebastian Ott
ce322ccd53 [S390] cio: obtain mdc value per channel path
Add support to accumulate the number of 64K-bytes blocks all paths
to a device at least support for a transport command.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:28 +01:00
Heiko Carstens
37e8952174 [S390] nohz: optimize arch_needs_cpu()
arch_needs_cpu() gets always executed on the current cpu. Therefore
the cpu parameter can be ignored it is possible to use __get_cpu_var()
instead of per_cpu() to access the per_cpu variable, which will
generate better code.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:28 +01:00
Jan Glauber
3d6c76ff32 [S390] qdio: outbound tasklet scan threshold
Introduce a scan treshold for the qdio outbound queues. By setting the
threshold the driver can tell qdio after how much used SBALs qdio
should schedule the outbound tasklet that scans the queue for finished
SBALs. The threshold is specific by the drivers because a
Hipersockets device is much faster in utilizing outbound buffers than a
ZFCP or OSA device.

The default values after how many used SBALs the tasklet should run are:

OSA:          > 31 SBALs
Hipersockets: > 7 SBALs
zfcp:         > 55 SBALs

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:28 +01:00
Michael Holzheu
2fcb3686e1 [S390] hypfs: Move buffer allocation from open to read
Currently the buffer for diagnose data is allocated in the open function
of the debugfs file and is released in the close function. This has the
drawback that a user (root) can pin that memory by not closing the file.
This patch moves the buffer allocation to the read function. The buffer is
automatically released after the buffer is copied to userspace.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:27 +01:00
Martin Schwidefsky
6432c015b7 [S390] current_thread_info optimization
Use thread_info lowcore field for current_thread_info(), saves
an unnecessary calculation.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:27 +01:00
Heiko Carstens
b1b7509185 [S390] extint: get rid of early code plus cleanup
Get rid of register/unregister_early_external_interrupt() and clean up
the code while at it.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:26 +01:00
Heiko Carstens
fb0a9d7e86 [S390] pfault: delay register of pfault interrupt
Use an early init call to initialize pfault. That way it is possible to
use the register_external_interrupt() instead of the early variant.
No need to enable pfault any earlier since it has only effect if user
space processes are running.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:26 +01:00
Holger Dengler
62d146ffe3 [S390] ap bus: add support for irq statistics
Add support for AP Bus I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Holger Dengler <hd@linux.vnet.ibm.com>
Signed-off-by: Felix Beck <felix.beck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:26 +01:00
Heiko Carstens
85b81cdd0b [S390] ctc: add support for irq statistics
Add support for CTC I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:26 +01:00
Heiko Carstens
355eb4022b [S390] claw: add support for irq statistics
Add support for CLAW I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:26 +01:00
Heiko Carstens
096a61682e [S390] lcs: add support for irq statistics
Add support for LCS I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:26 +01:00
Heiko Carstens
f48198d592 [S390] vmur: add support for irq statistics
Add support for VMUR I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:26 +01:00
Heiko Carstens
b86651721f [S390] tape: add support for irq statistics
Add support for ccw based tape I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:25 +01:00
Heiko Carstens
3fe22f6bfd [S390] 3270: add support for irq statistics
Add support for 3270 I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:25 +01:00
Heiko Carstens
12fae5858c [S390] 3215: add support for irq statistics
Add support for 3215 I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:25 +01:00
Heiko Carstens
3283942b71 [S390] dasd: add support for irq statistics
Add support for DASD I/O interrupt statistics in /proc/interrupts.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:25 +01:00
Jan Glauber
30d77c3e1c [S390] qdio: add qdio interrupts to interrupt statistics
Count traditional qdio interrupts and adapter interrupts for qdio
in the interrupt statistics.

Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:25 +01:00
Heiko Carstens
052ff461c8 [S390] irq: have detailed statistics for interrupt types
Up to now /proc/interrupts only has statistics for external and i/o
interrupts but doesn't split up them any further.
This patch adds a line for every single interrupt source so that it
is possible to easier tell what the machine is/was doing.
Part of the output now looks like this;

           CPU0       CPU2       CPU4
EXT:       3898       4232       2305
I/O:        782        315        245
CLK:       1029       1964        727   [EXT] Clock Comparator
IPI:       2868       2267       1577   [EXT] Signal Processor
TMR:          0          0          0   [EXT] CPU Timer
TAL:          0          0          0   [EXT] Timing Alert
PFL:          0          0          0   [EXT] Pseudo Page Fault
[...]
NMI:          0          1          1   [NMI] Machine Checks

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:25 +01:00
Heiko Carstens
545b288dcb [S390] time: let local_tick_enable/disable() reprogram the clock comparator
Let local_tick_enable/disable() reprogram the clock comparator so the
function names make semantically more sense.
Also that way the functions are more symmetric since normally each
local_tick_enable() call usually would have a subsequent call to
set_clock_comparator() anyway.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:25 +01:00
Heiko Carstens
17eb7a5cfa [S390] time: move local_tick_enable()/disable() to timex.h
Move the two functions to timex.h where they make more sense than in
hardirq.h.
No functional change.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:24 +01:00
Martin Schwidefsky
860dba45e8 [S390] add kprobes annotations
Add kprobes annotations to get the massive 'probe kernel.function("*") {}'
stress test working.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:24 +01:00
Martin Schwidefsky
4a1886358b [S390] kprobes: coding style
Correct some minor coding style issues.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:24 +01:00
Martin Schwidefsky
0e917cc329 [S390] kprobes: restructure handler function
Restructure the kprobe breakpoint handler function. Add comments to
make it more comprehensible and add a sanity check for re-entering
kprobes.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:24 +01:00
Martin Schwidefsky
92b8cbf17a [S390] kprobes: jprobe save and restore
Register %r14 and %r15 are already stored in jprobe_saved_regs, no need
to store them a second time in jprobe_saved_r14 / jprobe_saved_r15.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:24 +01:00
Martin Schwidefsky
371db06b01 [S390] kprobes: insn slots
The s390 architecture can execute code on kmalloc/vmalloc memory.
No need for the __ARCH_WANT_KPROBES_INSN_SLOT detour.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:24 +01:00
Martin Schwidefsky
b9599798f9 [S390] kprobes: activation and deactivation
Replace set_current_kprobe/reset_current_kprobe/save_previous_kprobe/
restore_previous_kprobe with a simpler scheme push_kprobe/pop_kprobe.
The mini kprobes stack can store up to two active kprobes.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:24 +01:00
Martin Schwidefsky
ba640a5915 [S390] kprobes: instruction fixup
Determine instruction fixup details in resume_execution, no need to do
it beforehand. Remove fixup, ilen and reg from arch_specific_insn.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:23 +01:00
Martin Schwidefsky
5a8b589f8a [S390] kprobes: instruction swap
Move the definition of the helper structure ins_replace_args to the
only place where it is used and drop the old member as it is not needed.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:23 +01:00
Martin Schwidefsky
fc0a1fea6b [S390] kprobes: single step cleanup
The saved interrupt mask and the saved control registers are only
relevant while single stepping is set up. A secondary kprobe while
kprobe single stepping is active may not occur. That makes is safe
to remove the save and restore of kprobe_saved_imask / kprobe_save_ctl
from save_previous_kprobe and restore_previous_kprobe.
Move all single step related code to two functions, enable_singlestep
and disable_singlestep.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:23 +01:00
Martin Schwidefsky
35f2aaa79a [S390] kprobes: single stepped breakpoint
Remove special case of a kprobe on a breakpoint while a relocated
instruction is single stepped. The only instruction that may cause
a fault while kprobe single stepping is active is the relocated
instruction. There is no kprobe on the instruction slot retrieved
with get_insn_slot().

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:23 +01:00
Martin Schwidefsky
6f9a3c3306 [S390] cleanup s390 Kconfig
Make use of def_bool and def_tristate where possible and add sensible
defaults to the config symbols where applicable. This shortens the
defconfig file by another ~40 lines.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2011-01-05 12:47:23 +01:00
David S. Miller
17f7f4d9fc Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Conflicts:
	net/ipv4/fib_frontend.c
2010-12-26 22:37:05 -08:00
Einar Lueck
d0ddf30fdd qeth: support ipv6 query arp cache for HiperSockets
Function qeth_l3_arp_query now queries for IPv6 addresses, too, if
QETH_QARP_WITH_IPV6 is passed as parameter to the ioctl. HiperSockets
and GuestLAN in HiperSockets mode provide corresponding entries.

Signed-off-by: Einar Lueck <elelueck@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2010-12-10 14:28:47 -08:00
Ingo Molnar
8e9255e6a2 Merge branch 'linus' into sched/core
Merge reason: we want to queue up dependent cleanup

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-12-08 20:15:29 +01:00
Heiko Carstens
398812159e [S390] nohz/s390: fix arch_needs_cpu() return value on offline cpus
This fixes the same problem as described in the patch "nohz: fix
printk_needs_cpu() return value on offline cpus" for the arch_needs_cpu()
primitive:

arch_needs_cpu() may return 1 if called on offline cpus. When a cpu gets
offlined it schedules the idle process which, before killing its own cpu,
will call tick_nohz_stop_sched_tick().
That function in turn will call arch_needs_cpu() in order to check if the
local tick can be disabled. On offline cpus this function should naturally
return 0 since regardless if the tick gets disabled or not the cpu will be
dead short after. That is besides the fact that __cpu_disable() should already
have made sure that no interrupts on the offlined cpu will be delivered anyway.

In this case it prevents tick_nohz_stop_sched_tick() to call
select_nohz_load_balancer(). No idea if that really is a problem. However what
made me debug this is that on 2.6.32 the function get_nohz_load_balancer() is
used within __mod_timer() to select a cpu on which a timer gets enqueued.
If arch_needs_cpu() returns 1 then the nohz_load_balancer cpu doesn't get
updated when a cpu gets offlined. It may contain the cpu number of an offline
cpu. In turn timers get enqueued on an offline cpu and not very surprisingly
they never expire and cause system hangs.

This has been observed 2.6.32 kernels. On current kernels __mod_timer() uses
get_nohz_timer_target() which doesn't have that problem. However there might
be other problems because of the too early exit tick_nohz_stop_sched_tick()
in case a cpu goes offline.

This specific bug was indrocuded with 3c5d92a0 "nohz: Introduce
arch_needs_cpu".

In this case a cpu hotplug notifier is used to fix the issue in order to keep
the normal/fast path small. All we need to do is to clear the condition that
makes arch_needs_cpu() return 1 since it is just a performance improvement
which is supposed to keep the local tick running for a short period if a cpu
goes idle. Nothing special needs to be done except for clearing the condition.

Cc: stable@kernel.org
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2010-12-01 10:08:17 +01:00