user/sven/linux.git/kernel, branch v3.0-rc2

rcu: Cure load woes

2011-05-31T08:01:48Z

Commit cc3ce5176d83 (rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state) fudges a sleeping task' state, resulting in the scheduler seeing a TASK_UNINTERRUPTIBLE task going to sleep, but a TASK_INTERRUPTIBLE task waking up. The result is unbalanced load calculation. The problem that patch tried to address is that the RCU threads could stay in UNINTERRUPTIBLE state for quite a while and triggering the hung task detector due to on-demand wake-ups. Cure the problem differently by always giving the tasks at least one wake-up once the CPU is fully up and running, this will kick them out of the initial UNINTERRUPTIBLE state and into the regular INTERRUPTIBLE wait state. [ The alternative would be teaching kthread_create() to start threads as INTERRUPTIBLE but that needs a tad more thought. ] Reported-by: Damien Wyart Signed-off-by: Peter Zijlstra Acked-by: Paul E. McKenney Link: http://lkml.kernel.org/r/1306755291.1200.2872.camel@twins Signed-off-by: Ingo Molnar

mm: Fix boot crash in mm_alloc()

2011-05-29T18:32:28Z

Thomas Gleixner reports that we now have a boot crash triggered by CONFIG_CPUMASK_OFFSTACK=y: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] find_next_bit+0x55/0xb0 Call Trace: [] cpumask_any_but+0x2a/0x70 [] flush_tlb_mm+0x2b/0x80 [] pud_populate+0x35/0x50 [] pgd_alloc+0x9a/0xf0 [] mm_init+0xec/0x120 [] mm_alloc+0x53/0xd0 which was introduced by commit de03c72cfce5 ("mm: convert mm->cpu_vm_cpumask into cpumask_var_t"), and is due to wrong ordering of mm_init() vs mm_init_cpumask Thomas wrote a patch to just fix the ordering of initialization, but I hate the new double allocation in the fork path, so I ended up instead doing some more radical surgery to clean it all up. Reported-by: Thomas Gleixner Reported-by: Ingo Molnar Cc: KOSAKI Motohiro Cc: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6

2011-05-29T18:18:09Z

* 'idle-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-idle-2.6: x86 idle: deprecate mwait_idle() and "idle=mwait" cmdline param x86 idle: deprecate "no-hlt" cmdline param x86 idle APM: deprecate CONFIG_APM_CPU_IDLE x86 idle floppy: deprecate disable_hlt() x86 idle: EXPORT_SYMBOL(default_idle, pm_idle) only when APM demands it x86 idle: clarify AMD erratum 400 workaround idle governor: Avoid lock acquisition to read pm_qos before entering idle cpuidle: menu: fixed wrapping timers at 4.294 seconds

idle governor: Avoid lock acquisition to read pm_qos before entering idle

2011-05-29T04:50:59Z

Thanks to the reviews and comments by Rafael, James, Mark and Andi. Here's version 2 of the patch incorporating your comments and also some update to my previous patch comments. I noticed that before entering idle state, the menu idle governor will look up the current pm_qos target value according to the list of qos requests received. This look up currently needs the acquisition of a lock to access the list of qos requests to find the qos target value, slowing down the entrance into idle state due to contention by multiple cpus to access this list. The contention is severe when there are a lot of cpus waking and going into idle. For example, for a simple workload that has 32 pair of processes ping ponging messages to each other, where 64 cpu cores are active in test system, I see the following profile with 37.82% of cpu cycles spent in contention of pm_qos_lock: - 37.82% swapper [kernel.kallsyms] [k] _raw_spin_lock_irqsave - _raw_spin_lock_irqsave - 95.65% pm_qos_request menu_select cpuidle_idle_call - cpu_idle 99.98% start_secondary A better approach will be to cache the updated pm_qos target value so reading it does not require lock acquisition as in the patch below. With this patch the contention for pm_qos_lock is removed and I saw a 2.2X increase in throughput for my message passing workload. cc: stable@kernel.org Signed-off-by: Tim Chen Acked-by: Andi Kleen Acked-by: James Bottomley Acked-by: mark gross Signed-off-by: Len Brown

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-05-28T19:56:46Z

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: cpuset: Fix cpuset_cpus_allowed_fallback(), don't update tsk->rt.nr_cpus_allowed sched: Fix ->min_vruntime calculation in dequeue_entity() sched: Fix ttwu() for __ARCH_WANT_INTERRUPTS_ON_CTXSW sched: More sched_domain iterations fixes

Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-05-28T19:56:32Z

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state rcu: Remove waitqueue usage for cpu, node, and boost kthreads rcu: Avoid acquiring rcu_node locks in timer functions atomic: Add atomic_or() Documentation: Add statistics about nested locks rcu: Decrease memory-barrier usage based on semi-formal proof rcu: Make rcu_enter_nohz() pay attention to nesting rcu: Don't do reschedule unless in irq rcu: Remove old memory barriers from rcu_process_callbacks() rcu: Add memory barriers rcu: Fix unpaired rcu_irq_enter() from locking selftests

Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2011-05-28T19:55:55Z

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (25 commits) perf: Fix SIGIO handling perf top: Don't stop if no kernel symtab is found perf top: Handle kptr_restrict perf top: Remove unused macro perf events: initialize fd array to -1 instead of 0 perf tools: Make sure kptr_restrict warnings fit 80 col terms perf tools: Fix build on older systems perf symbols: Handle /proc/sys/kernel/kptr_restrict perf: Remove duplicate headers ftrace: Add internal recursive checks tracing: Update btrfs's tracepoints to use u64 interface tracing: Add __print_symbolic_u64 to avoid warnings on 32bit machine ftrace: Set ops->flag to enabled even on static function tracing tracing: Have event with function tracer check error return ftrace: Have ftrace_startup() return failure code jump_label: Check entries limit in __jump_label_update ftrace/recordmcount: Avoid STT_FUNC symbols as base on ARM scripts/tags.sh: Add magic for trace-events for etags too scripts/tags.sh: Fix ctags for DEFINE_EVENT() x86/ftrace: Fix compiler warning in ftrace.c ...

rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state

2011-05-28T15:41:56Z

Upon creation, kthreads are in TASK_UNINTERRUPTIBLE state, which can result in softlockup warnings. Because some of RCU's kthreads can legitimately be idle indefinitely, start them in TASK_INTERRUPTIBLE state in order to avoid those warnings. Suggested-by: Peter Zijlstra Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Tested-by: Yinghai Lu Signed-off-by: Ingo Molnar

rcu: Remove waitqueue usage for cpu, node, and boost kthreads

2011-05-28T15:41:52Z

It is not necessary to use waitqueues for the RCU kthreads because we always know exactly which thread is to be awakened. In addition, wake_up() only issues an actual wakeup when there is a thread waiting on the queue, which was why there was an extra explicit wake_up_process() to get the RCU kthreads started. Eliminating the waitqueues (and wake_up()) in favor of wake_up_process() eliminates the need for the initial wake_up_process() and also shrinks the data structure size a bit. The wakeup logic is placed in a new rcu_wait() macro. Signed-off-by: Peter Zijlstra Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar

rcu: Avoid acquiring rcu_node locks in timer functions

2011-05-28T15:41:49Z

This commit switches manipulations of the rcu_node ->wakemask field to atomic operations, which allows rcu_cpu_kthread_timer() to avoid acquiring the rcu_node lock. This should avoid the following lockdep splat reported by Valdis Kletnieks: [ 12.872150] usb 1-4: new high speed USB device number 3 using ehci_hcd [ 12.986667] usb 1-4: New USB device found, idVendor=413c, idProduct=2513 [ 12.986679] usb 1-4: New USB device strings: Mfr=0, Product=0, SerialNumber=0 [ 12.987691] hub 1-4:1.0: USB hub found [ 12.987877] hub 1-4:1.0: 3 ports detected [ 12.996372] input: PS/2 Generic Mouse as /devices/platform/i8042/serio1/input/input10 [ 13.071471] udevadm used greatest stack depth: 3984 bytes left [ 13.172129] [ 13.172130] ======================================================= [ 13.172425] [ INFO: possible circular locking dependency detected ] [ 13.172650] 2.6.39-rc6-mmotm0506 #1 [ 13.172773] ------------------------------------------------------- [ 13.172997] blkid/267 is trying to acquire lock: [ 13.173009] (&p->pi_lock){-.-.-.}, at: [] try_to_wake_up+0x29/0x1aa [ 13.173009] [ 13.173009] but task is already holding lock: [ 13.173009] (rcu_node_level_0){..-...}, at: [] rcu_cpu_kthread_timer+0x27/0x58 [ 13.173009] [ 13.173009] which lock already depends on the new lock. [ 13.173009] [ 13.173009] [ 13.173009] the existing dependency chain (in reverse order) is: [ 13.173009] [ 13.173009] -> #2 (rcu_node_level_0){..-...}: [ 13.173009] [] check_prevs_add+0x8b/0x104 [ 13.173009] [] validate_chain+0x36f/0x3ab [ 13.173009] [] __lock_acquire+0x369/0x3e2 [ 13.173009] [] lock_acquire+0xfc/0x14c [ 13.173009] [] _raw_spin_lock+0x36/0x45 [ 13.173009] [] rcu_read_unlock_special+0x8c/0x1d5 [ 13.173009] [] __rcu_read_unlock+0x4f/0xd7 [ 13.173009] [] rcu_read_unlock+0x21/0x23 [ 13.173009] [] cpuacct_charge+0x6c/0x75 [ 13.173009] [] update_curr+0x101/0x12e [ 13.173009] [] check_preempt_wakeup+0xf7/0x23b [ 13.173009] [] check_preempt_curr+0x2b/0x68 [ 13.173009] [] ttwu_do_wakeup+0x76/0x128 [ 13.173009] [] ttwu_do_activate.constprop.63+0x57/0x5c [ 13.173009] [] scheduler_ipi+0x48/0x5d [ 13.173009] [] smp_reschedule_interrupt+0x16/0x18 [ 13.173009] [] reschedule_interrupt+0x13/0x20 [ 13.173009] [] rcu_read_unlock+0x21/0x23 [ 13.173009] [] find_get_page+0xa9/0xb9 [ 13.173009] [] filemap_fault+0x6a/0x34d [ 13.173009] [] __do_fault+0x54/0x3e6 [ 13.173009] [] handle_pte_fault+0x12c/0x1ed [ 13.173009] [] handle_mm_fault+0x1cd/0x1e0 [ 13.173009] [] do_page_fault+0x42d/0x5de [ 13.173009] [] page_fault+0x1f/0x30 [ 13.173009] [ 13.173009] -> #1 (&rq->lock){-.-.-.}: [ 13.173009] [] check_prevs_add+0x8b/0x104 [ 13.173009] [] validate_chain+0x36f/0x3ab [ 13.173009] [] __lock_acquire+0x369/0x3e2 [ 13.173009] [] lock_acquire+0xfc/0x14c [ 13.173009] [] _raw_spin_lock+0x36/0x45 [ 13.173009] [] __task_rq_lock+0x8b/0xd3 [ 13.173009] [] wake_up_new_task+0x41/0x108 [ 13.173009] [] do_fork+0x265/0x33f [ 13.173009] [] kernel_thread+0x6b/0x6d [ 13.173009] [] rest_init+0x21/0xd2 [ 13.173009] [] start_kernel+0x3bb/0x3c6 [ 13.173009] [] x86_64_start_reservations+0xaf/0xb3 [ 13.173009] [] x86_64_start_kernel+0xf0/0xf7 [ 13.173009] [ 13.173009] -> #0 (&p->pi_lock){-.-.-.}: [ 13.173009] [] check_prev_add+0x68/0x20e [ 13.173009] [] check_prevs_add+0x8b/0x104 [ 13.173009] [] validate_chain+0x36f/0x3ab [ 13.173009] [] __lock_acquire+0x369/0x3e2 [ 13.173009] [] lock_acquire+0xfc/0x14c [ 13.173009] [] _raw_spin_lock_irqsave+0x44/0x57 [ 13.173009] [] try_to_wake_up+0x29/0x1aa [ 13.173009] [] wake_up_process+0x10/0x12 [ 13.173009] [] rcu_cpu_kthread_timer+0x44/0x58 [ 13.173009] [] call_timer_fn+0xac/0x1e9 [ 13.173009] [] run_timer_softirq+0x1aa/0x1f2 [ 13.173009] [] __do_softirq+0x109/0x26a [ 13.173009] [] call_softirq+0x1c/0x30 [ 13.173009] [] do_softirq+0x44/0xf1 [ 13.173009] [] irq_exit+0x58/0xc8 [ 13.173009] [] smp_apic_timer_interrupt+0x79/0x87 [ 13.173009] [] apic_timer_interrupt+0x13/0x20 [ 13.173009] [] get_page_from_freelist+0x2aa/0x310 [ 13.173009] [] __alloc_pages_nodemask+0x178/0x243 [ 13.173009] [] pte_alloc_one+0x1e/0x3a [ 13.173009] [] __pte_alloc+0x22/0x14b [ 13.173009] [] handle_mm_fault+0x17e/0x1e0 [ 13.173009] [] do_page_fault+0x42d/0x5de [ 13.173009] [] page_fault+0x1f/0x30 [ 13.173009] [ 13.173009] other info that might help us debug this: [ 13.173009] [ 13.173009] Chain exists of: [ 13.173009] &p->pi_lock --> &rq->lock --> rcu_node_level_0 [ 13.173009] [ 13.173009] Possible unsafe locking scenario: [ 13.173009] [ 13.173009] CPU0 CPU1 [ 13.173009] ---- ---- [ 13.173009] lock(rcu_node_level_0); [ 13.173009] lock(&rq->lock); [ 13.173009] lock(rcu_node_level_0); [ 13.173009] lock(&p->pi_lock); [ 13.173009] [ 13.173009] *** DEADLOCK *** [ 13.173009] [ 13.173009] 3 locks held by blkid/267: [ 13.173009] #0: (&mm->mmap_sem){++++++}, at: [] do_page_fault+0x1f3/0x5de [ 13.173009] #1: (&yield_timer){+.-...}, at: [] call_timer_fn+0x0/0x1e9 [ 13.173009] #2: (rcu_node_level_0){..-...}, at: [] rcu_cpu_kthread_timer+0x27/0x58 [ 13.173009] [ 13.173009] stack backtrace: [ 13.173009] Pid: 267, comm: blkid Not tainted 2.6.39-rc6-mmotm0506 #1 [ 13.173009] Call Trace: [ 13.173009] [] print_circular_bug+0xc8/0xd9 [ 13.173009] [] check_prev_add+0x68/0x20e [ 13.173009] [] ? save_stack_trace+0x28/0x46 [ 13.173009] [] check_prevs_add+0x8b/0x104 [ 13.173009] [] validate_chain+0x36f/0x3ab [ 13.173009] [] __lock_acquire+0x369/0x3e2 [ 13.173009] [] ? try_to_wake_up+0x29/0x1aa [ 13.173009] [] lock_acquire+0xfc/0x14c [ 13.173009] [] ? try_to_wake_up+0x29/0x1aa [ 13.173009] [] ? rcu_check_quiescent_state+0x82/0x82 [ 13.173009] [] _raw_spin_lock_irqsave+0x44/0x57 [ 13.173009] [] ? try_to_wake_up+0x29/0x1aa [ 13.173009] [] try_to_wake_up+0x29/0x1aa [ 13.173009] [] ? rcu_check_quiescent_state+0x82/0x82 [ 13.173009] [] wake_up_process+0x10/0x12 [ 13.173009] [] rcu_cpu_kthread_timer+0x44/0x58 [ 13.173009] [] ? rcu_check_quiescent_state+0x82/0x82 [ 13.173009] [] call_timer_fn+0xac/0x1e9 [ 13.173009] [] ? del_timer+0x75/0x75 [ 13.173009] [] ? rcu_check_quiescent_state+0x82/0x82 [ 13.173009] [] run_timer_softirq+0x1aa/0x1f2 [ 13.173009] [] __do_softirq+0x109/0x26a [ 13.173009] [] ? tick_dev_program_event+0x37/0xf6 [ 13.173009] [] ? time_hardirqs_off+0x1b/0x2f [ 13.173009] [] call_softirq+0x1c/0x30 [ 13.173009] [] do_softirq+0x44/0xf1 [ 13.173009] [] irq_exit+0x58/0xc8 [ 13.173009] [] smp_apic_timer_interrupt+0x79/0x87 [ 13.173009] [] apic_timer_interrupt+0x13/0x20 [ 13.173009] [] ? get_page_from_freelist+0x114/0x310 [ 13.173009] [] ? get_page_from_freelist+0x2aa/0x310 [ 13.173009] [] ? clear_page_c+0x7/0x10 [ 13.173009] [] ? prep_new_page+0x14c/0x1cd [ 13.173009] [] get_page_from_freelist+0x2aa/0x310 [ 13.173009] [] __alloc_pages_nodemask+0x178/0x243 [ 13.173009] [] ? __pmd_alloc+0x87/0x99 [ 13.173009] [] pte_alloc_one+0x1e/0x3a [ 13.173009] [] ? __pmd_alloc+0x87/0x99 [ 13.173009] [] __pte_alloc+0x22/0x14b [ 13.173009] [] handle_mm_fault+0x17e/0x1e0 [ 13.173009] [] do_page_fault+0x42d/0x5de [ 13.173009] [] ? sys_brk+0x32/0x10c [ 13.173009] [] ? time_hardirqs_off+0x1b/0x2f [ 13.173009] [] ? trace_hardirqs_off_caller+0x3f/0x9c [ 13.173009] [] ? trace_hardirqs_off_thunk+0x3a/0x3c [ 13.173009] [] page_fault+0x1f/0x30 [ 14.010075] usb 5-1: new full speed USB device number 2 using uhci_hcd Reported-by: Valdis Kletnieks Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar