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* Merge branch 'for-linus' of git://git390.marist.edu/pub/scm/linux-2.6Linus Torvalds2011-01-0747-1276/+1357
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * '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 ...
| * [S390] prevent unneccesary loops_per_jiffy recalculationHeiko Carstens2011-01-051-1/+1
| | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] cpuinfo: use get_online_cpus() instead of preempt_disable()Heiko Carstens2011-01-051-4/+3
| | | | | | | | | | | | | | | | | | | | 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>
| * [S390] smp: remove cpu hotplug messagesHeiko Carstens2011-01-053-16/+0
| | | | | | | | | | | | | | | | | | | | 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>
| * [S390] mutex: enable spinning mutex on s390Gerald Schaefer2011-01-051-1/+0
| | | | | | | | | | | | | | | | 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>
| * [S390] mutex: Introduce arch_mutex_cpu_relax()Gerald Schaefer2011-01-052-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] cleanup ftrace backend functionsMartin Schwidefsky2011-01-054-171/+135
| | | | | | | | Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| * [S390] ptrace cleanupMartin Schwidefsky2011-01-0515-263/+347
| | | | | | | | | | | | | | Overhaul program event recording and the code dealing with the ptrace user space interface. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| * [S390] smp/idle: call init_idle() before starting a new cpuHeiko Carstens2011-01-053-7/+5
| | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] smp: delay idle task creationHeiko Carstens2011-01-051-15/+26
| | | | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] dasd: Add support for raw ECKD access.Stefan Haberland2011-01-051-0/+2
| | | | | | | | | | | | | | | | | | | | 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>
| * [S390] dasd: Improve handling of stolen DASD reservationStefan Weinhuber2011-01-051-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] nmi: enable machine checks earlyHeiko Carstens2011-01-051-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] 31 bit entry.S update.Martin Schwidefsky2011-01-051-103/+109
| | | | | | | | | | | | | | | | 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>
| * [S390] cio: obtain mdc value per channel pathSebastian Ott2011-01-051-0/+2
| | | | | | | | | | | | | | | | 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>
| * [S390] nohz: optimize arch_needs_cpu()Heiko Carstens2011-01-051-1/+1
| | | | | | | | | | | | | | | | | | | | 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>
| * [S390] qdio: outbound tasklet scan thresholdJan Glauber2011-01-051-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] hypfs: Move buffer allocation from open to readMichael Holzheu2011-01-056-118/+195
| | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] current_thread_info optimizationMartin Schwidefsky2011-01-051-1/+1
| | | | | | | | | | | | | | Use thread_info lowcore field for current_thread_info(), saves an unnecessary calculation. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| * [S390] extint: get rid of early code plus cleanupHeiko Carstens2011-01-052-103/+51
| | | | | | | | | | | | | | | | 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>
| * [S390] pfault: delay register of pfault interruptHeiko Carstens2011-01-053-15/+15
| | | | | | | | | | | | | | | | | | | | 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>
| * [S390] ap bus: add support for irq statisticsHolger Dengler2011-01-052-0/+2
| | | | | | | | | | | | | | | | 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>
| * [S390] ctc: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] claw: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] lcs: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] vmur: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] tape: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] 3270: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] 3215: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] dasd: add support for irq statisticsHeiko Carstens2011-01-052-0/+2
| | | | | | | | | | | | | | 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>
| * [S390] qdio: add qdio interrupts to interrupt statisticsJan Glauber2011-01-052-0/+4
| | | | | | | | | | | | | | | | 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>
| * [S390] irq: have detailed statistics for interrupt typesHeiko Carstens2011-01-057-19/+44
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] time: let local_tick_enable/disable() reprogram the clock comparatorHeiko Carstens2011-01-052-2/+2
| | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] time: move local_tick_enable()/disable() to timex.hHeiko Carstens2011-01-052-16/+18
| | | | | | | | | | | | | | | | | | 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>
| * [S390] add kprobes annotationsMartin Schwidefsky2011-01-058-9/+26
| | | | | | | | | | | | | | Add kprobes annotations to get the massive 'probe kernel.function("*") {}' stress test working. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| * [S390] kprobes: coding styleMartin Schwidefsky2011-01-051-34/+34
| | | | | | | | | | | | Correct some minor coding style issues. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
| * [S390] kprobes: restructure handler functionMartin Schwidefsky2011-01-051-43/+71
| | | | | | | | | | | | | | | | 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>
| * [S390] kprobes: jprobe save and restoreMartin Schwidefsky2011-01-052-13/+8
| | | | | | | | | | | | | | 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>
| * [S390] kprobes: insn slotsMartin Schwidefsky2011-01-052-10/+1
| | | | | | | | | | | | | | 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>
| * [S390] kprobes: activation and deactivationMartin Schwidefsky2011-01-051-32/+27
| | | | | | | | | | | | | | | | 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>
| * [S390] kprobes: instruction fixupMartin Schwidefsky2011-01-052-78/+57
| | | | | | | | | | | | | | 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>
| * [S390] kprobes: instruction swapMartin Schwidefsky2011-01-052-12/+9
| | | | | | | | | | | | | | 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>
| * [S390] kprobes: single step cleanupMartin Schwidefsky2011-01-052-44/+36
| | | | | | | | | | | | | | | | | | | | | | | | 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>
| * [S390] kprobes: single stepped breakpointMartin Schwidefsky2011-01-051-6/+0
| | | | | | | | | | | | | | | | | | | | 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>
| * [S390] cleanup s390 KconfigMartin Schwidefsky2011-01-054-164/+130
| | | | | | | | | | | | | | | | 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>
* | Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6Linus Torvalds2011-01-061-10/+41
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * 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 ...
| * | Merge branch 'master' of ↵David S. Miller2010-12-278-33/+105
| |\| | | | | | | | | | | | | | | | | | | master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 Conflicts: net/ipv4/fib_frontend.c
| * | qeth: support ipv6 query arp cache for HiperSocketsEinar Lueck2010-12-101-10/+41
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* | | Merge branch 'linus' into sched/coreIngo Molnar2010-12-083-11/+32
|\ \ \ | | |/ | |/| | | | | | | | | | Merge reason: we want to queue up dependent cleanup Signed-off-by: Ingo Molnar <mingo@elte.hu>
| * | [S390] nohz/s390: fix arch_needs_cpu() return value on offline cpusHeiko Carstens2010-12-011-0/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
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