When the timer tick fires, it accounts the new jiffy as either part
of system, user or idle time. This is how we record the cputime
statistics.
But when the tick is stopped from the idle task, we still need
to record the number of jiffies spent tickless until we restart
the tick and fall back to traditional tick-based cputime accounting.
To do this, we take a snapshot of jiffies when the tick is stopped
and compute the difference against the new value of jiffies when
the tick is restarted. Then we account this whole difference to
the idle cputime.
However we are preparing to be able to stop the tick from other places
than idle. So this idle time accounting needs to be performed from
the callers of nohz APIs, not from the nohz APIs themselves because
we now want them to be agnostic against places that stop/restart tick.
Therefore, we pull the tickless idle time accounting out of generic
nohz helpers up to idle entry/exit callers.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Merge RCU fixes from Paul E. McKenney:
" This series has four patches, the major point of which is to eliminate
some slowdowns (including boot-time slowdowns) resulting from some
RCU_FAST_NO_HZ changes. The issue with the changes is that posting timers
from the idle loop has no effect if the CPU has entered dyntick-idle
mode because the CPU has already computed its wakeup time, and posting
a timer does not cause it to be recomputed. The short-term fix is for
RCU to precompute the timeout value so that the CPU's calculation is
correct. "
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fix lots of new kernel-doc warnings in kernel/sched/fair.c:
Warning(kernel/sched/fair.c:3625): No description found for parameter 'env'
Warning(kernel/sched/fair.c:3625): Excess function parameter 'sd' description in 'update_sg_lb_stats'
Warning(kernel/sched/fair.c:3735): No description found for parameter 'env'
Warning(kernel/sched/fair.c:3735): Excess function parameter 'sd' description in 'update_sd_pick_busiest'
Warning(kernel/sched/fair.c:3735): Excess function parameter 'this_cpu' description in 'update_sd_pick_busiest'
.. more warnings
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull perf fixes from Ingo Molnar:
"A bit larger than what I'd wish for - half of it is due to hw driver
updates to Intel Ivy-Bridge which info got recently released,
cycles:pp should work there now too, amongst other things. (but we
are generally making exceptions for hardware enablement of this type.)
There are also callchain fixes in it - responding to mostly
theoretical (but valid) concerns. The tooling side sports perf.data
endianness/portability fixes which did not make it for the merge
window - and various other fixes as well."
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (26 commits)
perf/x86: Check user address explicitly in copy_from_user_nmi()
perf/x86: Check if user fp is valid
perf: Limit callchains to 127
perf/x86: Allow multiple stacks
perf/x86: Update SNB PEBS constraints
perf/x86: Enable/Add IvyBridge hardware support
perf/x86: Implement cycles:p for SNB/IVB
perf/x86: Fix Intel shared extra MSR allocation
x86/decoder: Fix bsr/bsf/jmpe decoding with operand-size prefix
perf: Remove duplicate invocation on perf_event_for_each
perf uprobes: Remove unnecessary check before strlist__delete
perf symbols: Check for valid dso before creating map
perf evsel: Fix 32 bit values endianity swap for sample_id_all header
perf session: Handle endianity swap on sample_id_all header data
perf symbols: Handle different endians properly during symbol load
perf evlist: Pass third argument to ioctl explicitly
perf tools: Update ioctl documentation for PERF_IOC_FLAG_GROUP
perf tools: Make --version show kernel version instead of pull req tag
perf tools: Check if callchain is corrupted
perf callchain: Make callchain cursors TLS
...
Pull leap second timer fix from Thomas Gleixner.
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timekeeping: Fix CLOCK_MONOTONIC inconsistency during leapsecond
This reverts commit 40af1bbdca.
It's horribly and utterly broken for at least the following reasons:
- calling sync_mm_rss() from mmput() is fundamentally wrong, because
there's absolutely no reason to believe that the task that does the
mmput() always does it on its own VM. Example: fork, ptrace, /proc -
you name it.
- calling it *after* having done mmdrop() on it is doubly insane, since
the mm struct may well be gone now.
- testing mm against NULL before you call it is insane too, since a
NULL mm there would have caused oopses long before.
.. and those are just the three bugs I found before I decided to give up
looking for me and revert it asap. I should have caught it before I
even took it, but I trusted Andrew too much.
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm->rss_stat counters have per-task delta: task->rss_stat. Before
changing task->mm pointer the kernel must flush this delta with
sync_mm_rss().
do_exit() already calls sync_mm_rss() to flush the rss-counters before
committing the rss statistics into task->signal->maxrss, taskstats,
audit and other stuff. Unfortunately the kernel does this before
calling mm_release(), which can call put_user() for processing
task->clear_child_tid. So at this point we can trigger page-faults and
task->rss_stat becomes non-zero again. As a result mm->rss_stat becomes
inconsistent and check_mm() will print something like this:
| BUG: Bad rss-counter state mm:ffff88020813c380 idx:1 val:-1
| BUG: Bad rss-counter state mm:ffff88020813c380 idx:2 val:1
This patch moves sync_mm_rss() into mm_release(), and moves mm_release()
out of do_exit() and calls it earlier. After mm_release() there should
be no pagefaults.
[akpm@linux-foundation.org: tweak comment]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@vger.kernel.org> [3.4.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In commit b76437579d ("procfs: mark thread stack correctly in
proc/<pid>/maps") the stack allocated via clone() is marked in
/proc/<pid>/maps as [stack:%d] thus it might be out of the former
mm->start_stack/end_stack values (and even has some custom VMA flags
set).
So to be able to restore mm->start_stack/end_stack drop vma flags test,
but still require the underlying VMA to exist.
As always note this feature is under CONFIG_CHECKPOINT_RESTORE and
requires CAP_SYS_RESOURCE to be granted.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Zero is written at clear_tid_address when the process exits. This
functionality is used by pthread_join().
We already have sys_set_tid_address() to change this address for the
current task but there is no way to obtain it from user space.
Without the ability to find this address and dump it we can't restore
pthread'ed apps which call pthread_join() once they have been restored.
This patch introduces the PR_GET_TID_ADDRESS prctl option which allows
the current process to obtain own clear_tid_address.
This feature is available iif CONFIG_CHECKPOINT_RESTORE is set.
[akpm@linux-foundation.org: fix prctl numbering]
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pedro Alves <palves@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a CPU is entering dyntick-idle mode, tick_nohz_stop_sched_tick()
calls rcu_needs_cpu() see if RCU needs that CPU, and, if not, computes the
next wakeup time based on the timer wheels. Only later, when actually
entering the idle loop, rcu_prepare_for_idle() will be invoked. In some
cases, rcu_prepare_for_idle() will post timers to wake the CPU back up.
But all for naught: The next wakeup time for the CPU has already been
computed, and posting a timer afterwards does not force that wakeup
time to be recomputed. This means that rcu_prepare_for_idle()'s have
no effect.
This is not a problem on a busy system because something else will wake
up the CPU soon enough. However, on lightly loaded systems, the CPU
might stay asleep for a considerable length of time. If that CPU has
a callback that the rest of the system is waiting on, the system might
run very slowly or (in theory) even hang.
This commit avoids this problem by having rcu_needs_cpu() give
tick_nohz_stop_sched_tick() an estimate of when RCU will need the CPU
to wake back up, which tick_nohz_stop_sched_tick() takes into account
when programming the CPU's wakeup time. An alternative approach is
for rcu_prepare_for_idle() to use hrtimers instead of normal timers,
but timers are much more efficient than are hrtimers for frequently
and repeatedly posting and cancelling a given timer, which is exactly
what RCU_FAST_NO_HZ does.
Reported-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
The RCU_FAST_NO_HZ code relies on a number of per-CPU variables.
This works, but is hidden from someone scanning the data structures
in rcutree.h. This commit therefore converts these per-CPU variables
to fields in the per-CPU rcu_dynticks structures.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
In the current code, a short dyntick-idle interval (where there is
at least one non-lazy callback on the CPU) and a long dyntick-idle
interval (where there are only lazy callbacks on the CPU) are traced
identically, which can be less than helpful. This commit therefore
emits different event traces in these two cases.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
In the present implementations of CPU hotplug, the outgoing CPU is
guaranteed to run its stop-machine process on the way out, which
will guarantee that RCU_FAST_NO_HZ forces the CPU out of dyntick-idle
mode.
However, new versions of CPU hotplug might not work this way. This
commit therefore removes this design constraint by explicitly notifying
CPUs when they adopt non-lazy RCU callbacks.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Tested-by: Pascal Chapperon <pascal.chapperon@wanadoo.fr>
A recent update to have tracing_on/off() only affect the ftrace ring
buffers instead of all ring buffers had a cut and paste error.
The tracing_off() did the exact same thing as tracing_on() and
would not actually turn off tracing. Unfortunately, tracing_off()
is more important to be working than tracing_on() as this is a key
development tool, as it lets the developer turn off tracing as soon
as a problem is discovered. It is also used by panic and oops code.
This bug also breaks the 'echo func:traceoff > set_ftrace_filter'
Cc: <stable@vger.kernel.org> # 3.4
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
It was introduced for memcg to iterate cgroup hierarchy without
holding cgroup_mutex, but soon after that it was replaced with
a lockless way in memcg.
No one used hierarchy_mutex since that, so remove it.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
__css_put is using atomic_dec on the ref count, and then
looking at the ref count to make decisions. This is prone
to races, as someone else may decrement ref count between
our decrement and our decision. Instead, we should base our
decisions on the value that we decremented the ref count to.
(This results in an actual race on Google's kernel which I
haven't been able to reproduce on the upstream kernel. Having
said that, it's still incorrect by inspection).
Signed-off-by: Salman Qazi <sqazi@google.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Kill the no longer needed uprobes_srcu/uprobe_srcu_id code.
It doesn't really work anyway. synchronize_srcu() can only
synchronize with the code "inside" the
srcu_read_lock/srcu_read_unlock section, while
uprobe_pre_sstep_notifier() does srcu_read_lock() _after_ we
already hit the breakpoint.
I guess this probably works "in practice". synchronize_srcu() is
slow and it implies synchronize_sched(), and the probed task
enters the non- preemptible section at the start of exception
handler. Still this is not right at least in theory, and
task->uprobe_srcu_id blows task_struct.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529193008.GG8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
