The code in find_idlest_cpu() looks for the CPU with the smallest load.
However, if multiple CPUs are idle, the first idle CPU is selected
irrespective of the depth of its idle state.
Among the idle CPUs we should pick the one with with the shallowest idle
state, or the latest to have gone idle if all idle CPUs are in the same
state. The later applies even when cpuidle is configured out.
This patch doesn't cover the following issues:
- The idle exit latency of a CPU might be larger than the time needed
to migrate the waking task to an already running CPU with sufficient
capacity, and therefore performance would benefit from task packing
in such case (in most cases task packing is about power saving).
- Some idle states have a non negligible and non abortable entry latency
which needs to run to completion before the exit latency can start.
A concurrent patch series is making this info available to the cpuidle
core. Once available, the entry latency with the idle timestamp could
determine when the exit latency may be effective.
Those issues will be handled in due course. In the mean time, what
is implemented here should improve things already compared to the current
state of affairs.
Based on an initial patch from Daniel Lezcano.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-pm@vger.kernel.org
Cc: linaro-kernel@lists.linaro.org
Link: http://lkml.kernel.org/n/tip-@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When the cpu enters idle, it stores the cpuidle state pointer in its
struct rq instance which in turn could be used to make a better decision
when balancing tasks.
As soon as the cpu exits its idle state, the struct rq reference is
cleared.
There are a couple of situations where the idle state pointer could be changed
while it is being consulted:
1. For x86/acpi with dynamic c-states, when a laptop switches from battery
to AC that could result on removing the deeper idle state. The acpi driver
triggers:
'acpi_processor_cst_has_changed'
'cpuidle_pause_and_lock'
'cpuidle_uninstall_idle_handler'
'kick_all_cpus_sync'.
All cpus will exit their idle state and the pointed object will be set to
NULL.
2. The cpuidle driver is unloaded. Logically that could happen but not
in practice because the drivers are always compiled in and 95% of them are
not coded to unregister themselves. In any case, the unloading code must
call 'cpuidle_unregister_device', that calls 'cpuidle_pause_and_lock'
leading to 'kick_all_cpus_sync' as mentioned above.
A race can happen if we use the pointer and then one of these two scenarios
occurs at the same moment.
In order to be safe, the idle state pointer stored in the rq must be
used inside a rcu_read_lock section where we are protected with the
'rcu_barrier' in the 'cpuidle_uninstall_idle_handler' function. The
idle_get_state() and idle_put_state() accessors should be used to that
effect.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: linux-pm@vger.kernel.org
Cc: linaro-kernel@lists.linaro.org
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In wake_affine() I have tried to understand the meaning of the condition:
(this_load <= load &&
this_load + target_load(prev_cpu, idx) <= tl_per_task)
but I failed to find a use case that can take advantage of it and I haven't
found clear description in the previous commit's log.
Futhermore, the comment of the condition refers to the task_hot function that
was used before being replaced by the current condition:
/*
* This domain has SD_WAKE_AFFINE and
* p is cache cold in this domain, and
* there is no bad imbalance.
*/
If we look more deeply the below condition:
this_load + target_load(prev_cpu, idx) <= tl_per_task
When sync is clear, we have:
tl_per_task = runnable_load_avg / nr_running
this_load = max(runnable_load_avg, cpuload[idx])
target_load = max(runnable_load_avg', cpuload'[idx])
It implies that runnable_load_avg == 0 and nr_running <= 1 in order to match the
condition. This implies that runnable_load_avg == 0 too because of the
condition: this_load <= load.
but if this _load is null, 'balanced' is already set and the test is redundant.
If sync is set, it's not as straight forward as above (especially if cgroup
are involved) but the policy should be similar as we have removed a task that's
going to sleep in order to get a more accurate load and this_load values.
The current conclusion is that these additional condition don't give any benefit
so we can remove them.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: preeti@linux.vnet.ibm.com
Cc: riel@redhat.com
Cc: Morten.Rasmussen@arm.com
Cc: efault@gmx.de
Cc: nicolas.pitre@linaro.org
Cc: daniel.lezcano@linaro.org
Cc: dietmar.eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1409051215-16788-3-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The imbalance flag can stay set whereas there is no imbalance.
Let assume that we have 3 tasks that run on a dual cores /dual cluster system.
We will have some idle load balance which are triggered during tick.
Unfortunately, the tick is also used to queue background work so we can reach
the situation where short work has been queued on a CPU which already runs a
task. The load balance will detect this imbalance (2 tasks on 1 CPU and an idle
CPU) and will try to pull the waiting task on the idle CPU. The waiting task is
a worker thread that is pinned on a CPU so an imbalance due to pinned task is
detected and the imbalance flag is set.
Then, we will not be able to clear the flag because we have at most 1 task on
each CPU but the imbalance flag will trig to useless active load balance
between the idle CPU and the busy CPU.
We need to reset of the imbalance flag as soon as we have reached a balanced
state. If all tasks are pinned, we don't consider that as a balanced state and
let the imbalance flag set.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: riel@redhat.com
Cc: Morten.Rasmussen@arm.com
Cc: efault@gmx.de
Cc: nicolas.pitre@linaro.org
Cc: daniel.lezcano@linaro.org
Cc: dietmar.eggemann@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1409051215-16788-2-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The code in task_numa_compare() will only examine at most one idle CPU per node,
because they all have the same score. However, some idle CPUs are better
candidates than others, due to busy or idle SMT siblings, etc...
The scheduler has logic to find the best CPU within an LLC to place a
task. The NUMA code should probably use it.
This seems to reduce the standard deviation for single instance SPECjbb2005
with a low warehouse count on my 4 node test system.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: mgorman@suse.de
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140904163530.189d410a@cuia.bos.redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Current code can fail to migrate a waking task (silently) when TTWU_QUEUE is
enabled.
When a task is waking, it is pending on the wake_list of the rq, but it is not
queued (task->on_rq == 0). In this case, set_cpus_allowed_ptr() and
__migrate_task() will not migrate it because its invisible to them.
This behavior is incorrect, because the task has been already woken, it will be
running on the wrong CPU without correct placement until the next wake-up or
update for cpus_allowed.
To fix this problem, we need to finish the wakeup (so they appear on
the runqueue) before we migrate them.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Reported-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Tested-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/538ED7EB.5050303@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull ACPI and power management fixes from Rafael Wysocki:
"These are regression fixes (ACPI sysfs, ACPI video, suspend test),
ACPI cpuidle deadlock fix, missing runtime validation of ACPI _DSD
output, a fix and a new CPU ID for the RAPL driver, new blacklist
entry for the ACPI EC driver and a couple of trivial cleanups
(intel_pstate and generic PM domains).
Specifics:
- Fix for recently broken test_suspend= command line argument (Rafael
Wysocki).
- Fixes for regressions related to the ACPI video driver caused by
switching the default to native backlight handling in 3.16 from
Hans de Goede.
- Fix for a sysfs attribute of ACPI device objects that returns stale
values sometimes due to the fact that they are cached instead of
executing the appropriate method (_SUN) every time (broken in
3.14). From Yasuaki Ishimatsu.
- Fix for a deadlock between cpuidle_lock and cpu_hotplug.lock in the
ACPI processor driver from Jiri Kosina.
- Runtime output validation for the ACPI _DSD device configuration
object missing from the support for it that has been introduced
recently. From Mika Westerberg.
- Fix for an unuseful and misleading RAPL (Running Average Power
Limit) domain detection message in the RAPL driver from Jacob Pan.
- New Intel Haswell CPU ID for the RAPL driver from Jason Baron.
- New Clevo W350etq blacklist entry for the ACPI EC driver from Lan
Tianyu.
- Cleanup for the intel_pstate driver and the core generic PM domains
code from Gabriele Mazzotta and Geert Uytterhoeven"
* tag 'pm+acpi-3.17-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock
ACPI / scan: not cache _SUN value in struct acpi_device_pnp
cpufreq: intel_pstate: Remove unneeded variable
powercap / RAPL: change domain detection message
powercap / RAPL: add support for CPU model 0x3f
PM / domains: Make generic_pm_domain.name const
PM / sleep: Fix test_suspend= command line option
ACPI / EC: Add msi quirk for Clevo W350etq
ACPI / video: Disable native_backlight on HP ENVY 15 Notebook PC
ACPI / video: Add a disable_native_backlight quirk
ACPI / video: Fix use_native_backlight selection logic
ACPICA: ACPI 5.1: Add support for runtime validation of _DSD package.
Pull RCU fix from Ingo Molnar:
"A boot hang fix for the offloaded callback RCU model (RCU_NOCB_CPU=y
&& (TREE_CPU=y || TREE_PREEMPT_RC)) in certain bootup scenarios"
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rcu: Make nocb leader kthreads process pending callbacks after spawning
Pull timer fixes from Thomas Gleixner:
"Three fixlets from the timer departement:
- Update the timekeeper before updating vsyscall and pvclock. This
fixes the kvm-clock regression reported by Chris and Paolo.
- Use the proper irq work interface from NMI. This fixes the
regression reported by Catalin and Dave.
- Clarify the compat_nanosleep error handling mechanism to avoid
future confusion"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timekeeping: Update timekeeper before updating vsyscall and pvclock
compat: nanosleep: Clarify error handling
nohz: Restore NMI safe local irq work for local nohz kick
An overrun could happen in function start_hrtick_dl()
when a task with SCHED_DEADLINE runs in the microseconds
range.
For example, if a task with SCHED_DEADLINE has the following parameters:
Task runtime deadline period
P1 200us 500us 500us
The deadline and period from task P1 are less than 1ms.
In order to achieve microsecond precision, we need to enable HRTICK feature
by the next command:
PC#echo "HRTICK" > /sys/kernel/debug/sched_features
PC#trace-cmd record -e sched_switch &
PC#./schedtool -E -t 200000:500000:500000 -e ./test
The binary test is in an endless while(1) loop here.
Some pieces of trace.dat are as follows:
<idle>-0 157.603157: sched_switch: :R ==> 2481:4294967295: test
test-2481 157.603203: sched_switch: 2481:R ==> 0:120: swapper/2
<idle>-0 157.605657: sched_switch: :R ==> 2481:4294967295: test
test-2481 157.608183: sched_switch: 2481:R ==> 2483:120: trace-cmd
trace-cmd-2483 157.609656: sched_switch:2483:R==>2481:4294967295: test
We can get the runtime of P1 from the information above:
runtime = 157.608183 - 157.605657
runtime = 0.002526(2.526ms)
The correct runtime should be less than or equal to 200us at some point.
The problem is caused by a conditional judgment "delta > 10000"
in function start_hrtick_dl().
Because no hrtimer start up to control the rest of runtime
when the reset of runtime is less than 10us.
So the process will continue to run until tick-period is coming.
Move the code with the limit of the least time slice
from hrtick_start_fair() to hrtick_start() because the
EDF schedule class also needs this function in start_hrtick_dl().
To fix this problem, we call hrtimer_start() unconditionally in
start_hrtick_dl(), and make sure the scheduling slice won't be smaller
than 10us in hrtimer_start().
Signed-off-by: Xiaofeng Yan <xiaofeng.yan@huawei.com>
Reviewed-by: Li Zefan <lizefan@huawei.com>
Acked-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1409022941-5880-1-git-send-email-xiaofeng.yan@huawei.com
[ Massaged the changelog and the code. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The update_walltime() code works on the shadow timekeeper to make the
seqcount protected region as short as possible. But that update to the
shadow timekeeper does not update all timekeeper fields because it's
sufficient to do that once before it becomes life. One of these fields
is tkr.base_mono. That stays stale in the shadow timekeeper unless an
operation happens which copies the real timekeeper to the shadow.
The update function is called after the update calls to vsyscall and
pvclock. While not correct, it did not cause any problems because none
of the invoked update functions used base_mono.
commit cbcf2dd3b3 (x86: kvm: Make kvm_get_time_and_clockread()
nanoseconds based) changed that in the kvm pvclock update function, so
the stale mono_base value got used and caused kvm-clock to malfunction.
Put the update where it belongs and fix the issue.
Reported-by: Chris J Arges <chris.j.arges@canonical.com>
Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409050000570.3333@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The error handling in compat_sys_nanosleep() is correct, but
completely non obvious. Document it and restrict it to the
-ERESTART_RESTARTBLOCK return value for clarity.
Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The use of "rcu_assign_pointer()" is NULLing out the pointer.
According to RCU_INIT_POINTER()'s block comment:
"1. This use of RCU_INIT_POINTER() is NULLing out the pointer"
it is better to use it instead of rcu_assign_pointer() because it has a
smaller overhead.
The following Coccinelle semantic patch was used:
@@
@@
- rcu_assign_pointer
+ RCU_INIT_POINTER
(..., NULL)
Signed-off-by: Andreea-Cristina Bernat <bernat.ada@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: paulmck@linux.vnet.ibm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140822145043.GA580@ada
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The local nohz kick is currently used by perf which needs it to be
NMI-safe. Recent commit though (7d1311b93e)
changed its implementation to fire the local kick using the remote kick
API. It was convenient to make the code more generic but the remote kick
isn't NMI-safe.
As a result:
WARNING: CPU: 3 PID: 18062 at kernel/irq_work.c:72 irq_work_queue_on+0x11e/0x140()
CPU: 3 PID: 18062 Comm: trinity-subchil Not tainted 3.16.0+ #34
0000000000000009 00000000903774d1 ffff880244e06c00 ffffffff9a7f1e37
0000000000000000 ffff880244e06c38 ffffffff9a0791dd ffff880244fce180
0000000000000003 ffff880244e06d58 ffff880244e06ef8 0000000000000000
Call Trace:
<NMI> [<ffffffff9a7f1e37>] dump_stack+0x4e/0x7a
[<ffffffff9a0791dd>] warn_slowpath_common+0x7d/0xa0
[<ffffffff9a07930a>] warn_slowpath_null+0x1a/0x20
[<ffffffff9a17ca1e>] irq_work_queue_on+0x11e/0x140
[<ffffffff9a10a2c7>] tick_nohz_full_kick_cpu+0x57/0x90
[<ffffffff9a186cd5>] __perf_event_overflow+0x275/0x350
[<ffffffff9a184f80>] ? perf_event_task_disable+0xa0/0xa0
[<ffffffff9a01a4cf>] ? x86_perf_event_set_period+0xbf/0x150
[<ffffffff9a187934>] perf_event_overflow+0x14/0x20
[<ffffffff9a020386>] intel_pmu_handle_irq+0x206/0x410
[<ffffffff9a0b54d3>] ? arch_vtime_task_switch+0x63/0x130
[<ffffffff9a01937b>] perf_event_nmi_handler+0x2b/0x50
[<ffffffff9a007b72>] nmi_handle+0xd2/0x390
[<ffffffff9a007aa5>] ? nmi_handle+0x5/0x390
[<ffffffff9a0d131b>] ? lock_release+0xab/0x330
[<ffffffff9a008062>] default_do_nmi+0x72/0x1c0
[<ffffffff9a0c925f>] ? cpuacct_account_field+0xcf/0x200
[<ffffffff9a008268>] do_nmi+0xb8/0x100
Lets fix this by restoring the use of local irq work for the nohz local
kick.
Reported-by: Catalin Iacob <iacobcatalin@gmail.com>
Reported-and-tested-by: Dave Jones <davej@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Pull an RCU fix from Paul E. McKenney:
"This series contains a single commit fixing an initialization bug
reported by Amit Shah and fixed by Pranith Kumar (and tested by Amit).
This bug results in a boot-time hang in callback-offloaded configurations
where callbacks were posted before the offloading ('rcuo') kthreads
were created."
Signed-off-by: Ingo Molnar <mingo@kernel.org>
After commit d431cbc53c (PM / sleep: Simplify sleep states sysfs
interface code) the pm_states[] array is not populated initially,
which causes setup_test_suspend() to always fail and the suspend
testing during boot doesn't work any more.
Fix the problem by using pm_labels[] instead of pm_states[] in
setup_test_suspend() and storing a pointer to the label of the
sleep state to test rather than the number representing it,
because the connection between the state numbers and labels is
only established by suspend_set_ops().
Fixes: d431cbc53c (PM / sleep: Simplify sleep states sysfs interface code)
Reported-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Pull irq handling fixlet from Thomas Gleixner:
"Just an export for an interrupt flow handler which is now used in gpio
modules"
* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irq: Export handle_fasteoi_irq
Currently new system call kexec_file_load() and all the associated code
compiles if CONFIG_KEXEC=y. But new syscall also compiles purgatory
code which currently uses gcc option -mcmodel=large. This option seems
to be available only gcc 4.4 onwards.
Hiding new functionality behind a new config option will not break
existing users of old gcc. Those who wish to enable new functionality
will require new gcc. Having said that, I am trying to figure out how
can I move away from using -mcmodel=large but that can take a while.
I think there are other advantages of introducing this new config
option. As this option will be enabled only on x86_64, other arches
don't have to compile generic kexec code which will never be used. This
new code selects CRYPTO=y and CRYPTO_SHA256=y. And all other arches had
to do this for CONFIG_KEXEC. Now with introduction of new config
option, we can remove crypto dependency from other arches.
Now CONFIG_KEXEC_FILE is available only on x86_64. So whereever I had
CONFIG_X86_64 defined, I got rid of that.
For CONFIG_KEXEC_FILE, instead of doing select CRYPTO=y, I changed it to
"depends on CRYPTO=y". This should be safer as "select" is not
recursive.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Tested-by: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Richard and Daniel reported that UML is broken due to changes to
resource traversal functions. Problem is that iomem_resource.child can
be null and new code does not consider that possibility. Old code used
a for loop and that loop will not even execute if p was null.
Revert back to for() loop logic and bail out if p is null.
I also moved sibling_only check out of resource_lock. There is no
reason to keep it inside the lock.
Following is backtrace of the UML crash.
RIP: 0033:[<0000000060039b9f>]
RSP: 0000000081459da0 EFLAGS: 00010202
RAX: 0000000000000000 RBX: 00000000219b3fff RCX: 000000006010d1d9
RDX: 0000000000000001 RSI: 00000000602dfb94 RDI: 0000000081459df8
RBP: 0000000081459de0 R08: 00000000601b59f4 R09: ffffffff0000ff00
R10: ffffffff0000ff00 R11: 0000000081459e88 R12: 0000000081459df8
R13: 00000000219b3fff R14: 00000000602dfb94 R15: 0000000000000000
Kernel panic - not syncing: Segfault with no mm
CPU: 0 PID: 1 Comm: swapper Not tainted 3.16.0-10454-g58d08e3 #13
Stack:
00000000 000080d0 81459df0 219b3fff
81459e70 6010d1d9 ffffffff 6033e010
81459e50 6003a269 81459e30 00000000
Call Trace:
[<6010d1d9>] ? kclist_add_private+0x0/0xe7
[<6003a269>] walk_system_ram_range+0x61/0xb7
[<6000e859>] ? proc_kcore_init+0x0/0xf1
[<6010d574>] kcore_update_ram+0x4c/0x168
[<6010d72e>] ? kclist_add+0x0/0x2e
[<6000e943>] proc_kcore_init+0xea/0xf1
[<6000e859>] ? proc_kcore_init+0x0/0xf1
[<6000e859>] ? proc_kcore_init+0x0/0xf1
[<600189f0>] do_one_initcall+0x13c/0x204
[<6004ca46>] ? parse_args+0x1df/0x2e0
[<6004c82d>] ? parameq+0x0/0x3a
[<601b5990>] ? strcpy+0x0/0x18
[<60001e1a>] kernel_init_freeable+0x240/0x31e
[<6026f1c0>] kernel_init+0x12/0x148
[<60019fad>] new_thread_handler+0x81/0xa3
Fixes 8c86e70ace ("resource: provide new functions to walk
through resources").
Reported-by: Daniel Walter <sahne@0x90.at>
Tested-by: Richard Weinberger <richard@nod.at>
Tested-by: Toralf Förster <toralf.foerster@gmx.de>
Tested-by: Daniel Walter <sahne@0x90.at>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The nocb callbacks generated before the nocb kthreads are spawned are
enqueued in the nocb queue for later processing. Commit fbce7497ee ("rcu:
Parallelize and economize NOCB kthread wakeups") introduced nocb leader kthreads
which checked the nocb_leader_wake flag to see if there were any such pending
callbacks. A case was reported in which newly spawned leader kthreads were not
processing the pending callbacks as this flag was not set, which led to a boot
hang.
The following commit ensures that the newly spawned nocb kthreads process the
pending callbacks by allowing the kthreads to run immediately after spawning
instead of waiting. This is done by inverting the logic of nocb_leader_wake
tests to nocb_leader_sleep which allows us to use the default initialization of
this flag to 0 to let the kthreads run.
Reported-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Link: http://www.spinics.net/lists/kernel/msg1802899.html
[ paulmck: Backported to v3.17-rc2. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Amit Shah <amit.shah@redhat.com>
Pull trace buffer epoll hang fix from Steven Rostedt:
"Josef Bacik found a bug in the ring_buffer_poll_wait() where the
condition variable (waiters_pending) was set before being added to the
poll queue via poll_wait(). This allowed for a small race window to
happen where an event could come in, check the condition variable see
it set to true, clear it, and then wake all the waiters. But because
the waiter set the variable before adding itself to the queue, the
waker could have cleared the variable after it was set and then miss
waking it up as it wasn't added to the queue yet.
Discussing this bug, we realized that a memory barrier needed to be
added too, for the rare case that something polls for a single trace
event to happen (and just one, no more to come in), and miss the
wakeup due to memory ordering. Ideally, a memory barrier needs to be
added on the writer side too, but as that will kill tracing
performance and this is for a situation that tracing wasn't even
designed for (who traces one instance of an event, use a printk
instead!), this isn't worth adding the barrier. But we can in the
future add the barrier for when the buffer goes from empty to the
first event, as that would cover this case"
* tag 'trace-fixes-v3.17-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
trace: Fix epoll hang when we race with new entries
Epoll on trace_pipe can sometimes hang in a weird case. If the ring buffer is
empty when we set waiters_pending but an event shows up exactly at that moment
we can miss being woken up by the ring buffers irq work. Since
ring_buffer_empty() is inherently racey we will sometimes think that the buffer
is not empty. So we don't get woken up and we don't think there are any events
even though there were some ready when we added the watch, which makes us hang.
This patch fixes this by making sure that we are actually on the wait list
before we set waiters_pending, and add a memory barrier to make sure
ring_buffer_empty() is going to be correct.
Link: http://lkml.kernel.org/p/1408989581-23727-1-git-send-email-jbacik@fb.com
Cc: stable@vger.kernel.org # 3.10+
Cc: Martin Lau <kafai@fb.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Pull fix for ftrace function tracer/profiler conflict from Steven Rostedt:
"The rewrite of the ftrace code that makes it possible to allow for
separate trampolines had a design flaw with the interaction between
the function and function_graph tracers.
The main flaw was the simplification of the use of multiple tracers
having the same filter (like function and function_graph, that use the
set_ftrace_filter file to filter their code). The design assumed that
the two tracers could never run simultaneously as only one tracer can
be used at a time. The problem with this assumption was that the
function profiler could be implemented on top of the function graph
tracer, and the function profiler could run at the same time as the
function tracer. This caused the assumption to be broken and when
ftrace detected this failed assumpiton it would spit out a nasty
warning and shut itself down.
Instead of using a single ftrace_ops that switches between the
function and function_graph callbacks, the two tracers can again use
their own ftrace_ops. But instead of having a complex hierarchy of
ftrace_ops, the filter fields are placed in its own structure and the
ftrace_ops can carefully use the same filter. This change took a bit
to be able to allow for this and currently only the global_ops can
share the same filter, but this new design can easily be modified to
allow for any ftrace_ops to share its filter with another ftrace_ops.
The first four patches deal with the change of allowing the ftrace_ops
to share the filter (and this needs to go to 3.16 as well).
The fifth patch fixes a bug that was also caused by the new changes
but only for archs other than x86, and only if those archs implement a
direct call to the function_graph tracer which they do not do yet but
will in the future. It does not need to go to stable, but needs to be
fixed before the other archs update their code to allow direct calls
to the function_graph trampoline"
* tag 'trace-fixes-v3.17-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
ftrace: Use current addr when converting to nop in __ftrace_replace_code()
ftrace: Fix function_profiler and function tracer together
ftrace: Fix up trampoline accounting with looping on hash ops
ftrace: Update all ftrace_ops for a ftrace_hash_ops update
ftrace: Allow ftrace_ops to use the hashes from other ops
