Impact: fix incorrect locking triggered during hotplug-intense stress-tests
While migrating the the CB_IRQSAFE_UNLOCKED timers during a cpu-offline,
we queue them on the cb_pending list, so that they won't go
stale.
Thus, when the callbacks of the timers run from the softirq context,
they could run into potential deadlocks, since these callbacks
assume that they're running with irq's disabled, thereby annoying
lockdep!
Fix this by emulating hardirq context while running these callbacks from
the hrtimer softirq.
=================================
[ INFO: inconsistent lock state ]
2.6.27 #2
--------------------------------
inconsistent {in-hardirq-W} -> {hardirq-on-W} usage.
ksoftirqd/0/4 [HC0[0]:SC1[1]:HE1:SE0] takes:
(&rq->lock){++..}, at: [<c011db84>] sched_rt_period_timer+0x9e/0x1fc
{in-hardirq-W} state was registered at:
[<c014103c>] __lock_acquire+0x549/0x121e
[<c0107890>] native_sched_clock+0x88/0x99
[<c013aa12>] clocksource_get_next+0x39/0x3f
[<c0139abc>] update_wall_time+0x616/0x7df
[<c0141d6b>] lock_acquire+0x5a/0x74
[<c0121724>] scheduler_tick+0x3a/0x18d
[<c047ed45>] _spin_lock+0x1c/0x45
[<c0121724>] scheduler_tick+0x3a/0x18d
[<c0121724>] scheduler_tick+0x3a/0x18d
[<c012c436>] update_process_times+0x3a/0x44
[<c013c044>] tick_periodic+0x63/0x6d
[<c013c062>] tick_handle_periodic+0x14/0x5e
[<c010568c>] timer_interrupt+0x44/0x4a
[<c0150c9f>] handle_IRQ_event+0x13/0x3d
[<c0151c14>] handle_level_irq+0x79/0xbd
[<c0105634>] do_IRQ+0x69/0x7d
[<c01041e4>] common_interrupt+0x28/0x30
[<c047007b>] aac_probe_one+0x1a3/0x3f3
[<c047ec2d>] _spin_unlock_irqrestore+0x36/0x39
[<c01512b4>] setup_irq+0x1be/0x1f9
[<c065d70b>] start_kernel+0x259/0x2c5
[<ffffffff>] 0xffffffff
irq event stamp: 50102
hardirqs last enabled at (50102): [<c047ebf4>] _spin_unlock_irq+0x20/0x23
hardirqs last disabled at (50101): [<c047edc2>] _spin_lock_irq+0xa/0x4b
softirqs last enabled at (50088): [<c0128ba6>] do_softirq+0x37/0x4d
softirqs last disabled at (50099): [<c0128ba6>] do_softirq+0x37/0x4d
other info that might help us debug this:
no locks held by ksoftirqd/0/4.
stack backtrace:
Pid: 4, comm: ksoftirqd/0 Not tainted 2.6.27 #2
[<c013f6cb>] print_usage_bug+0x13e/0x147
[<c013fef5>] mark_lock+0x493/0x797
[<c01410b1>] __lock_acquire+0x5be/0x121e
[<c0141d6b>] lock_acquire+0x5a/0x74
[<c011db84>] sched_rt_period_timer+0x9e/0x1fc
[<c047ed45>] _spin_lock+0x1c/0x45
[<c011db84>] sched_rt_period_timer+0x9e/0x1fc
[<c011db84>] sched_rt_period_timer+0x9e/0x1fc
[<c01210fd>] finish_task_switch+0x41/0xbd
[<c0107890>] native_sched_clock+0x88/0x99
[<c011dae6>] sched_rt_period_timer+0x0/0x1fc
[<c0136dda>] run_hrtimer_pending+0x54/0xe5
[<c011dae6>] sched_rt_period_timer+0x0/0x1fc
[<c0128afb>] __do_softirq+0x7b/0xef
[<c0128ba6>] do_softirq+0x37/0x4d
[<c0128c12>] ksoftirqd+0x56/0xc5
[<c0128bbc>] ksoftirqd+0x0/0xc5
[<c0134649>] kthread+0x38/0x5d
[<c0134611>] kthread+0x0/0x5d
[<c0104477>] kernel_thread_helper+0x7/0x10
=======================
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There's a small race/chance that, while hrtimers are enabled globally,
they're later not enabled when we're calling the hrtimer_interrupt() function,
which then BUG_ON()'s for that. This patch closes that race/gap.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Impact: per CPU hrtimers can be migrated from a dead CPU
The hrtimer code has no knowledge about per CPU timers, but we need to
prevent the migration of such timers and warn when such a timer is
active at migration time.
Explicitely mark the timers as per CPU and use a more understandable
mode descriptor for the interrupts safe unlocked callback mode, which
is used by hrtimer_sleeper and the scheduler code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: during migration active hrtimers can be seen as inactive
The migration code removes the hrtimers from the queues of the dead
CPU and sets the state temporary to INACTIVE. The enqueue code sets it
to ACTIVE/PENDING again.
Prevent that the wrong state can be seen by using a separate migration
state bit.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: Stale timers after a CPU went offline.
commit 37bb6cb409
hrtimer: unlock hrtimer_wakeup
changed the hrtimer sleeper callback mode to CB_IRQSAFE_NO_SOFTIRQ due
to locking problems. A result of this change is that when enqueue is
called for an already expired hrtimer the callback function is not
longer called directly from the enqueue code. The normal callers have
been fixed in the code, but the migration code which moves hrtimers
from a dead CPU to a live CPU was not made aware of this.
This can be fixed by checking the timer state after the call to
enqueue in the migration code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: hrtimers which are on the pending list are not migrated at cpu
offline and can be stale forever
Add the pending list migration when CONFIG_HIGH_RES_TIMERS is enabled
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Peter Zijlstra noticed this 8 months ago and I just noticed
it again.
hrtimer_clock_base::get_softirq_time() is currently unused
in the entire tree. In fact, looking at the logs, it appears
as if it was never used. Remove it.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
As part of going idle, we already look at the time of the next timer event to determine
which C-state to select etc.
This patch adds functionality that causes the timers that are past their
soft expire time, to fire at this time, before we calculate the next wakeup
time. This functionality will thus avoid wakeups by running timers before
going idle rather than specially waking up for it.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
This patch makes the nanosleep() system call use the per process
slack value; with this users are able to externally control existing
applications to reduce the wakeup rate.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
this patch adds a _range version of hrtimer_start() so that range timers
can be created; the hrtimer_start() function is just a wrapper around this.
In addition, hrtimer_start_expires() will now preserve existing ranges.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
this patch turns hrtimers into range timers; they have 2 expire points
1) the soft expire point
2) the hard expire point
the kernel will do it's regular best effort attempt to get the timer run
at the hard expire point. However, if some other time fires after the soft
expire point, the kernel now has the freedom to fire this timer at this point,
and thus grouping the events and preventing a power-expensive wakeup in the
future.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
In order to be able to do range hrtimers we need to use accessor functions
to the "expire" member of the hrtimer struct.
This patch converts kernel/* to these accessors.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
This patch adds a schedule_hrtimeout() function, to be used by select() and
poll() in a later patch. This function works similar to schedule_timeout()
in most ways, but takes a timespec rather than jiffies.
With a lot of contributions/fixes from Thomas
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add the comment to explain why the double lock in migrate_timers()
can't deadlock.
Change the code to use spinlock_irq() instead of local_irq_disable()
+ spin_lock().
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'timers/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
x86: add PCI ID for 6300ESB force hpet
x86: add another PCI ID for ICH6 force-hpet
kernel-paramaters: document pmtmr= command line option
acpi_pm clccksource: fix printk format warning
nohz: don't stop idle tick if softirqs are pending.
pmtmr: allow command line override of ioport
nohz: reduce jiffies polling overhead
hrtimer: Remove unused variables in ktime_divns()
hrtimer: remove warning in hres_timers_resume
posix-timers: print RT watchdog message
* 'for-linus' of master.kernel.org:/home/rmk/linux-2.6-arm: (241 commits)
[ARM] 5171/1: ep93xx: fix compilation of modules using clocks
[ARM] 5133/2: at91sam9g20 defconfig file
[ARM] 5130/4: Support for the at91sam9g20
[ARM] 5160/1: IOP3XX: gpio/gpiolib support
[ARM] at91: Fix NAND FLASH timings for at91sam9x evaluation kits.
[ARM] 5084/1: zylonite: Register AC97 device
[ARM] 5085/2: PXA: Move AC97 over to the new central device declaration model
[ARM] 5120/1: pxa: correct platform driver names for PXA25x and PXA27x UDC drivers
[ARM] 5147/1: pxaficp_ir: drop pxa_gpio_mode calls, as pin setting
[ARM] 5145/1: PXA2xx: provide api to control IrDA pins state
[ARM] 5144/1: pxaficp_ir: cleanup includes
[ARM] pxa: remove pxa_set_cken()
[ARM] pxa: allow clk aliases
[ARM] Feroceon: don't disable BPU on boot
[ARM] Orion: LED support for HP mv2120
[ARM] Orion: add RD88F5181L-FXO support
[ARM] Orion: add RD88F5181L-GE support
[ARM] Orion: add Netgear WNR854T support
[ARM] s3c2410_defconfig: update for current build
[ARM] Acer n30: Minor style and indentation fixes.
...
* 'core/softirq' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
softirq: remove irqs_disabled warning from local_bh_enable
softirq: remove initialization of static per-cpu variable
Remove argument from open_softirq which is always NULL
