Viresh Kumar
b5e995e671
nohz: Fix spurious periodic tick behaviour in low-res dynticks mode ...
When we reach the end of the tick handler, we unconditionally reschedule
the next tick to the next jiffy. Then on irq exit, the nohz code
overrides that setting if needed and defers the next tick as far away in
the future as possible.
Now in the best dynticks case, when we actually don't need any tick in
the future (ie: expires == KTIME_MAX), low-res and high-res behave
differently. What we want in this case is to cancel the next tick
programmed by the previous one. That's what we do in high-res mode. OTOH
we lack a low-res mode equivalent of hrtimer_cancel() so we simply don't
do anything in this case and the next tick remains scheduled to jiffies + 1.
As a result, in low-res mode, when the dynticks code determines that no
tick is needed in the future, we can recursively get a spurious tick
every jiffy because then the next tick is always reprogrammed from the
tick handler and is never cancelled. And this can happen indefinetly
until some subsystem actually needs a precise tick in the future and only
then we eventually overwrite the previous tick handler setting to defer
the next tick.
We are fixing this by introducing the ONESHOT_STOPPED mode which will
let us pause a clockevent when no further interrupt is needed. Meanwhile
we can't expect all drivers to support this new mode.
So lets reduce much of the symptoms by skipping the nohz-blind tick
rescheduling from the tick-handler when the CPU is in dynticks mode.
That tick rescheduling wrongly assumed periodicity and the low-res
dynticks code can't cancel such decision. This breaks the recursive (and
thus the worst) part of the problem. In the worst case now, we'll get
only one extra tick due to uncancelled tick scheduled before we entered
dynticks mode.
This also removes a needless clockevent write on idle ticks. Since those
clock write are usually considered to be slow, it's a general win.
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2014-08-22 18:46:49 +02:00
net: filter: split 'struct sk_filter' into socket and bpf parts
2014-08-02 15:03:58 -07:00
kdb: Use ktime_get_ts()
2014-06-12 16:18:45 +02:00
mm: memcontrol: rewrite charge API
2014-08-08 15:57:17 -07:00
kernel/gcov/fs.c: remove unnecessary null test before debugfs_remove
2014-08-08 15:57:24 -07:00
Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-08-05 17:38:45 -07:00
arch, locking: Ciao arch_mutex_cpu_relax()
2014-07-17 12:32:47 +02:00
Merge branches 'pm-sleep', 'pm-cpufreq' and 'pm-cpuidle'
2014-08-11 23:19:48 +02:00
printk: Add function to return log buffer address and size
2014-08-13 15:13:44 +10:00
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2014-08-04 15:55:08 -07:00
Merge branches 'pm-sleep', 'pm-cpufreq' and 'pm-cpuidle'
2014-08-11 23:19:48 +02:00
nohz: Fix spurious periodic tick behaviour in low-res dynticks mode
2014-08-22 18:46:49 +02:00
This contains a fix for two long standing bugs. Both of which are
2014-08-09 17:29:36 -07:00
kernel/acct.c: fix coding style warnings and errors
2014-08-08 15:57:27 -07:00
CAPABILITIES: remove undefined caps from all processes
2014-07-24 21:53:47 +10:00
kernel/auditfilter.c: replace count*size kmalloc by kcalloc
2014-08-06 18:01:12 -07:00
auditsc: audit_krule mask accesses need bounds checking
2014-06-10 08:44:40 -07:00
kernel/backtracetest.c: replace no level printk by pr_info()
2014-06-04 16:54:14 -07:00
page-cgroup: get rid of NR_PCG_FLAGS
2014-08-08 15:57:18 -07:00
CAPABILITIES: remove undefined caps from all processes
2014-07-24 21:53:47 +10:00
Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
2014-08-04 10:11:28 -07:00
cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes
2014-07-15 11:05:09 -04:00
kernel/compat.c: use sizeof() instead of sizeof
2014-06-04 16:54:19 -07:00
x86/kprobes: Fix build errors and blacklist context_track_user
2014-06-14 09:07:44 +02:00
sched: Rework check_for_tasks()
2014-07-05 11:17:45 +02:00
Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
2014-08-04 10:11:28 -07:00
delayacct: Remove braindamaged type conversions
2014-07-23 10:18:06 -07:00
kernel/exec_domain.c: code clean-up
2014-06-04 16:54:15 -07:00
kernel/exit.c: fix coding style warnings and errors
2014-08-08 15:57:22 -07:00
seccomp: Replace BUG(!spin_is_locked()) with assert_spin_lock
2014-08-11 13:29:12 -07:00
futex: Simplify futex_lock_pi_atomic() and make it more robust
2014-06-21 22:26:24 +02:00
kernel/hung_task.c: convert simple_strtoul to kstrtouint
2014-06-04 16:54:15 -07:00
irq_work: Remove BUG_ON in irq_work_run()
2014-07-05 11:17:26 +02:00
kernel/kallsyms.c: fix %pB when there's no symbol at the address
2014-08-08 15:57:18 -07:00
locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER
2014-07-16 14:57:13 +02:00
kexec: verify the signature of signed PE bzImage
2014-08-08 15:57:33 -07:00
signals: change wait_for_helper() to use kernel_sigaction()
2014-06-06 16:08:12 -07:00
kprobes: Fix "Failed to find blacklist" probing errors on ia64 and ppc64
2014-07-18 06:23:40 +02:00
kthread_work: wake up worker only when the worker is idle
2014-07-28 14:07:52 -04:00
kernel/latencytop.c: convert seq_printf to seq_puts
2014-06-04 16:54:15 -07:00
bin2c: move bin2c in scripts/basic
2014-08-08 15:57:32 -07:00
module: Clean up ro/nx after early module load failures
2014-08-16 04:47:00 +09:30
namespaces: Use task_lock and not rcu to protect nsproxy
2014-07-29 18:08:50 -07:00
panic: add TAINT_SOFTLOCKUP
2014-08-08 15:57:24 -07:00
Add module param type 'ullong'
2014-07-17 22:07:37 +02:00
kernel/profile.c: use static const char instead of static char
2014-06-06 16:08:13 -07:00
sched: Remove proliferation of wait_on_bit() action functions
2014-07-16 15:10:39 +02:00
kernel/reboot.c: convert simple_strtoul to kstrtoint
2014-06-04 16:54:15 -07:00
kernel/res_counter.c: replace simple_strtoull by kstrtoull
2014-06-04 16:54:15 -07:00
resource: provide new functions to walk through resources
2014-08-08 15:57:32 -07:00
seccomp: Replace BUG(!spin_is_locked()) with assert_spin_lock
2014-08-11 13:29:12 -07:00
Merge branch 'signal-cleanup' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/misc
2014-08-09 09:58:12 -07:00
kernel/smp.c:on_each_cpu_cond(): fix warning in fallback path
2014-08-06 18:01:22 -07:00
kernel/stop_machine.c: kernel-doc warning fix
2014-06-04 16:54:15 -07:00
sched: move no_new_privs into new atomic flags
2014-07-18 12:13:38 -07:00
kexec: new syscall kexec_file_load() declaration
2014-08-08 15:57:32 -07:00
mm, hugetlb: remove hugetlb_zero and hugetlb_infinity
2014-08-06 18:01:19 -07:00
ipv6: Allow accepting RA from local IP addresses.
2014-07-01 12:16:24 -07:00
KEYS: validate certificate trust only with builtin keys
2014-07-17 09:35:17 -04:00
kernel/test_kprobes.c: use current logging functions
2014-08-08 15:57:18 -07:00
torture: Avoid format string leak to thead name
2014-07-07 10:12:56 -07:00
tracing: syscall_regfunc() should not skip kernel threads
2014-06-21 00:15:26 -04:00
sched: Make task->start_time nanoseconds based
2014-07-23 10:18:05 -07:00
kernel/user.c: drop unused field 'files' from user_struct
2014-06-04 16:54:16 -07:00
proc: constify seq_operations
2014-08-08 15:57:22 -07:00
namespaces: Use task_lock and not rcu to protect nsproxy
2014-07-29 18:08:50 -07:00
sysctl: convert use of typedef ctl_table to struct ctl_table
2014-06-06 16:08:16 -07:00
panic: add TAINT_SOFTLOCKUP
2014-08-08 15:57:24 -07:00
Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu
2014-08-04 10:09:27 -07:00
b5e995e671