Modern kernel callback systems pass the structure associated with a
given callback to the callback function. The timer callback remains one
of the legacy cases where an arbitrary unsigned long argument continues
to be passed as the callback argument. This has several problems:
- This bloats the timer_list structure with a normally redundant
.data field.
- No type checking is being performed, forcing callbacks to do
explicit type casts of the unsigned long argument into the object
that was passed, rather than using container_of(), as done in most
of the other callback infrastructure.
- Neighboring buffer overflows can overwrite both the .function and
the .data field, providing attackers with a way to elevate from a buffer
overflow into a simplistic ROP-like mechanism that allows calling
arbitrary functions with a controlled first argument.
- For future Control Flow Integrity work, this creates a unique function
prototype for timer callbacks, instead of allowing them to continue to
be clustered with other void functions that take a single unsigned long
argument.
This adds a new timer initialization API, which will ultimately replace
the existing setup_timer(), setup_{deferrable,pinned,etc}_timer() family,
named timer_setup() (to mirror hrtimer_setup(), making instances of its
use much easier to grep for).
In order to support the migration of existing timers into the new
callback arguments, timer_setup() casts its arguments to the existing
legacy types, and explicitly passes the timer pointer as the legacy
data argument. Once all setup_*timer() callers have been replaced with
timer_setup(), the casts can be removed, and the data argument can be
dropped with the timer expiration code changed to just pass the timer
to the callback directly.
Since the regular pattern of using container_of() during local variable
declaration repeats the need for the variable type declaration
to be included, this adds a helper modeled after other from_*()
helpers that wrap container_of(), named from_timer(). This helper uses
typeof(*variable), removing the type redundancy and minimizing the need
for line wraps in forthcoming conversions from "unsigned data long" to
"struct timer_list *" in the timer callbacks:
-void callback(unsigned long data)
+void callback(struct timer_list *t)
{
- struct some_data_structure *local = (struct some_data_structure *)data;
+ struct some_data_structure *local = from_timer(local, t, timer);
Finally, in order to support the handful of timer users that perform
open-coded assignments of the .function (and .data) fields, provide
cast macros (TIMER_FUNC_TYPE and TIMER_DATA_TYPE) that can be used
temporarily. Once conversion has been completed, these can be globally
trivially removed.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20170928133817.GA113410@beast
So we want to simplify <linux/sched.h>'s header dependencies, but one
roadblock of that is <linux/timer.h>'s inclusion of sysctl.h,
which brings in other, problematic headers.
Note that timer.h's inclusion of sysctl.h can be avoided if we
pre-declare ctl_table - so do that.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
and small optimizations.
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Merge tag 'trace-v4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
"This release has no new tracing features, just clean ups, minor fixes
and small optimizations"
* tag 'trace-v4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (25 commits)
tracing: Remove outdated ring buffer comment
tracing/probes: Fix a warning message to show correct maximum length
tracing: Fix return value check in trace_benchmark_reg()
tracing: Use modern function declaration
jump_label: Reduce the size of struct static_key
tracing/probe: Show subsystem name in messages
tracing/hwlat: Update old comment about migration
timers: Make flags output in the timer_start tracepoint useful
tracing: Have traceprobe_probes_write() not access userspace unnecessarily
tracing: Have COMM event filter key be treated as a string
ftrace: Have set_graph_function handle multiple functions in one write
ftrace: Do not hold references of ftrace_graph_{notrace_}hash out of graph_lock
tracing: Reset parser->buffer to allow multiple "puts"
ftrace: Have set_graph_functions handle write with RDWR
ftrace: Reset fgd->hash in ftrace_graph_write()
ftrace: Replace (void *)1 with a meaningful macro name FTRACE_GRAPH_EMPTY
ftrace: Create a slight optimization on searching the ftrace_hash
tracing: Add ftrace_hash_key() helper function
ftrace: Convert graph filter to use hash tables
ftrace: Expose ftrace_hash_empty and ftrace_lookup_ip
...
The timer flags in the timer_start trace event contain lots of useful
information, but the meaning is not clear in the trace output. Making tools
rely on the bit positions is bad as they might change over time.
Decode the flags in the print out. Tools can retrieve the bits and their
meaning from the trace format file.
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1702101639290.4036@nanos
Requested-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Currently CONFIG_TIMER_STATS exposes process information across namespaces:
kernel/time/timer_list.c print_timer():
SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);
/proc/timer_list:
#11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570
Given that the tracer can give the same information, this patch entirely
removes CONFIG_TIMER_STATS.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: linux-doc@vger.kernel.org
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Xing Gao <xgao01@email.wm.edu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jessica Frazelle <me@jessfraz.com>
Cc: kernel-hardening@lists.openwall.com
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Michal Marek <mmarek@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-api@vger.kernel.org
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: http://lkml.kernel.org/r/20170208192659.GA32582@beast
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
When tearing down, call timers_dead_cpu() before notify_dead().
There is a hidden dependency between:
- timers
- block multiqueue
- rcutree
If timers_dead_cpu() comes later than blk_mq_queue_reinit_notify()
that latter function causes a RCU stall.
Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.566790058@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We now have implicit batching in the timer wheel. The slack API is no longer
used, so remove it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew F. Davis <afd@ti.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Pali Rohár <pali.rohar@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mmc@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.189813118@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The current timer wheel has some drawbacks:
1) Cascading:
Cascading can be an unbound operation and is completely pointless in most
cases because the vast majority of the timer wheel timers are canceled or
rearmed before expiration. (They are used as timeout safeguards, not as
real timers to measure time.)
2) No fast lookup of the next expiring timer:
In NOHZ scenarios the first timer soft interrupt after a long NOHZ period
must fast forward the base time to the current value of jiffies. As we
have no way to find the next expiring timer fast, the code loops linearly
and increments the base time one by one and checks for expired timers
in each step. This causes unbound overhead spikes exactly in the moment
when we should wake up as fast as possible.
After a thorough analysis of real world data gathered on laptops,
workstations, webservers and other machines (thanks Chris!) I came to the
conclusion that the current 'classic' timer wheel implementation can be
modified to address the above issues.
The vast majority of timer wheel timers is canceled or rearmed before
expiry. Most of them are timeouts for networking and other I/O tasks. The
nature of timeouts is to catch the exception from normal operation (TCP ack
timed out, disk does not respond, etc.). For these kinds of timeouts the
accuracy of the timeout is not really a concern. Timeouts are very often
approximate worst-case values and in case the timeout fires, we already
waited for a long time and performance is down the drain already.
The few timers which actually expire can be split into two categories:
1) Short expiry times which expect halfways accurate expiry
2) Long term expiry times are inaccurate today already due to the
batching which is done for NOHZ automatically and also via the
set_timer_slack() API.
So for long term expiry timers we can avoid the cascading property and just
leave them in the less granular outer wheels until expiry or
cancelation. Timers which are armed with a timeout larger than the wheel
capacity are no longer cascaded. We expire them with the longest possible
timeout (6+ days). We have not observed such timeouts in our data collection,
but at least we handle them, applying the rule of the least surprise.
To avoid extending the wheel levels for HZ=1000 so we can accomodate the
longest observed timeouts (5 days in the network conntrack code) we reduce the
first level granularity on HZ=1000 to 4ms, which effectively is the same as
the HZ=250 behaviour. From our data analysis there is nothing which relies on
that 1ms granularity and as a side effect we get better batching and timer
locality for the networking code as well.
Contrary to the classic wheel the granularity of the next wheel is not the
capacity of the first wheel. The granularities of the wheels are in the
currently chosen setting 8 times the granularity of the previous wheel.
So for HZ=250 we end up with the following granularity levels:
Level Offset Granularity Range
0 0 4 ms 0 ms - 252 ms
1 64 32 ms 256 ms - 2044 ms (256ms - ~2s)
2 128 256 ms 2048 ms - 16380 ms (~2s - ~16s)
3 192 2048 ms (~2s) 16384 ms - 131068 ms (~16s - ~2m)
4 256 16384 ms (~16s) 131072 ms - 1048572 ms (~2m - ~17m)
5 320 131072 ms (~2m) 1048576 ms - 8388604 ms (~17m - ~2h)
6 384 1048576 ms (~17m) 8388608 ms - 67108863 ms (~2h - ~18h)
7 448 8388608 ms (~2h) 67108864 ms - 536870911 ms (~18h - ~6d)
That's a worst case inaccuracy of 12.5% for the timers which are queued at the
beginning of a level.
So the new wheel concept addresses the old issues:
1) Cascading is avoided completely
2) By keeping the timers in the bucket until expiry/cancelation we can track
the buckets which have timers enqueued in a bucket bitmap and therefore can
look up the next expiring timer very fast and O(1).
A further benefit of the concept is that the slack calculation which is done
on every timer start is no longer necessary because the granularity levels
provide natural batching already.
Our extensive testing with various loads did not show any performance
degradation vs. the current wheel implementation.
This patch does not address the 'fast lookup' issue as we wanted to make sure
that there is no regression introduced by the wheel redesign. The
optimizations are in follow up patches.
This patch contains fixes from Anna-Maria Gleixner and Richard Cochran.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.108621834@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We want to store the array index in the flags space. 256k CPUs should be
enough for a while.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.030144293@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We switched all users to initialize the timers as pinned and call
mod_timer(). Remove the now unused timer API function.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.706205231@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We want to move the timer migration logic from a 'push' to a 'pull' model.
Under the current 'push' model pinned timers are handled via
a runtime API variant: mod_timer_pinned().
The 'pull' model requires us to store the pinned attribute of a timer
in the timer_list structure itself, as a new TIMER_PINNED bit in
timer->flags.
This flag must be set at initialization time and the timer APIs
recognize the flag.
This patch:
- Implements the new flag and associated new-style initialization
methods
- makes mod_timer() recognize new-style pinned timers,
- and adds some migration helper facility to allow
step by step conversion of old-style to new-style
pinned timers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.049338558@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Add the trivial missing macro to setup a deferrable timer.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Eric reported that the timer_migration sysctl is not really nice
performance wise as it needs to check at every timer insertion whether
the feature is enabled or not. Further the check does not live in the
timer code, so we have an extra function call which checks an extra
cache line to figure out that it is disabled.
We can do better and store that information in the per cpu (hr)timer
bases. I pondered to use a static key, but that's a nightmare to
update from the nohz code and the timer base cache line is hot anyway
when we select a timer base.
The old logic enabled the timer migration unconditionally if
CONFIG_NO_HZ was set even if nohz was disabled on the kernel command
line.
With this modification, we start off with migration disabled. The user
visible sysctl is still set to enabled. If the kernel switches to NOHZ
migration is enabled, if the user did not disable it via the sysctl
prior to the switch. If nohz=off is on the kernel command line,
migration stays disabled no matter what.
Before:
47.76% hog [.] main
14.84% [kernel] [k] _raw_spin_lock_irqsave
9.55% [kernel] [k] _raw_spin_unlock_irqrestore
6.71% [kernel] [k] mod_timer
6.24% [kernel] [k] lock_timer_base.isra.38
3.76% [kernel] [k] detach_if_pending
3.71% [kernel] [k] del_timer
2.50% [kernel] [k] internal_add_timer
1.51% [kernel] [k] get_nohz_timer_target
1.28% [kernel] [k] __internal_add_timer
0.78% [kernel] [k] timerfn
0.48% [kernel] [k] wake_up_nohz_cpu
After:
48.10% hog [.] main
15.25% [kernel] [k] _raw_spin_lock_irqsave
9.76% [kernel] [k] _raw_spin_unlock_irqrestore
6.50% [kernel] [k] mod_timer
6.44% [kernel] [k] lock_timer_base.isra.38
3.87% [kernel] [k] detach_if_pending
3.80% [kernel] [k] del_timer
2.67% [kernel] [k] internal_add_timer
1.33% [kernel] [k] __internal_add_timer
0.73% [kernel] [k] timerfn
0.54% [kernel] [k] wake_up_nohz_cpu
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Joonwoo Park <joonwoop@codeaurora.org>
Cc: Wenbo Wang <wenbo.wang@memblaze.com>
Link: http://lkml.kernel.org/r/20150526224512.127050787@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Simplify the handling of the flag storage for the timer statistics. No
intermediate storage anymore. Just hand over the flags field.
I left the printout of 'deferrable' for now because changing this
would be an ABI update and I have no idea how strong people feel about
that. OTOH, I wonder whether we should kill the whole timer stats
stuff because all of that information can be retrieved via ftrace/perf
as well.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Joonwoo Park <joonwoop@codeaurora.org>
Cc: Wenbo Wang <wenbo.wang@memblaze.com>
Link: http://lkml.kernel.org/r/20150526224512.046626248@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Instead of storing a pointer to the per cpu tvec_base we can simply
cache a CPU index in the timer_list and use that to get hold of the
correct per cpu tvec_base. This is only used in lock_timer_base() and
the slightly larger code is peanuts versus the spinlock operation and
the d-cache foot print of the timer wheel.
Aside of that this allows to get rid of following nuisances:
- boot_tvec_base
That statically allocated 4k bss data is just kept around so the
timer has a home when it gets statically initialized. It serves no
other purpose.
With the CPU index we assign the timer to CPU0 at static
initialization time and therefor can avoid the whole boot_tvec_base
dance. That also simplifies the init code, which just can use the
per cpu base.
Before:
text data bss dec hex filename
17491 9201 4160 30852 7884 ../build/kernel/time/timer.o
After:
text data bss dec hex filename
17440 9193 0 26633 6809 ../build/kernel/time/timer.o
- Overloading the base pointer with various flags
The CPU index has enough space to hold the flags (deferrable,
irqsafe) so we can get rid of the extra masking and bit fiddling
with the base pointer.
As a benefit we reduce the size of struct timer_list on 64 bit
machines. 4 - 8 bytes, a size reduction up to 15% per struct timer_list,
which is a real win as we have tons of them embedded in other structs.
This changes also the newly added deferrable printout of the timer
start trace point to capture and print all timer->flags, which allows
us to decode the target cpu of the timer as well.
We might have used bitfields for this, but that would change the
static initializers and the init function for no value to accomodate
big endian bitfields.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Joonwoo Park <joonwoop@codeaurora.org>
Cc: Wenbo Wang <wenbo.wang@memblaze.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Badhri Jagan Sridharan <Badhri@google.com>
Link: http://lkml.kernel.org/r/20150526224511.950084301@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This reduces the size of struct tvec_base by 50% and results in
slightly smaller code as well.
Before:
struct tvec_base: size: 8256, cachelines: 129
text data bss dec hex filename
17698 13297 8256 39251 9953 ../build/kernel/time/timer.o
After:
struct tvec_base: 4160, cachelines: 65
text data bss dec hex filename
17491 9201 4160 30852 7884 ../build/kernel/time/timer.o
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Joonwoo Park <joonwoop@codeaurora.org>
Cc: Wenbo Wang <wenbo.wang@memblaze.com>
Link: http://lkml.kernel.org/r/20150526224511.854731214@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The evaluation of the next timer in the nohz code is based on jiffies
while all the tick internals are nano seconds based. We have also to
convert hrtimer nanoseconds to jiffies in the !highres case. That's
just wrong and introduces interesting corner cases.
Turn it around and convert the next timer wheel timer expiry and the
rcu event to clock monotonic and base all calculations on
nanoseconds. That identifies the case where no timer is pending
clearly with an absolute expiry value of KTIME_MAX.
Makes the code more readable and gets rid of the jiffies magic in the
nohz code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Link: http://lkml.kernel.org/r/20150414203502.184198593@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Timer internals are protected with irq-safe locks but timer execution
isn't, so a timer being dequeued for execution and its execution
aren't atomic against IRQs. This makes it impossible to wait for its
completion from IRQ handlers and difficult to shoot down a timer from
IRQ handlers.
This issue caused some issues for delayed_work interface. Because
there's no way to reliably shoot down delayed_work->timer from IRQ
handlers, __cancel_delayed_work() can't share the logic to steal the
target delayed_work with cancel_delayed_work_sync(), and can only
steal delayed_works which are on queued on timer. Similarly, the
pending mod_delayed_work() can't be used from IRQ handlers.
This patch adds a new timer flag TIMER_IRQSAFE, which makes the timer
to be executed without enabling IRQ after dequeueing such that its
dequeueing and execution are atomic against IRQ handlers.
This makes it safe to wait for the timer's completion from IRQ
handlers, for example, using del_timer_sync(). It can never be
executing on the local CPU and if executing on other CPUs it won't be
interrupted until done.
This will enable simplifying delayed_work cancel/mod interface.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1344449428-24962-5-git-send-email-tj@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Over time, timer initializers became messy with unnecessarily
duplicated code which are inconsistently spread across timer.h and
timer.c.
This patch cleans up timer initializers.
* timer.c::__init_timer() is renamed to do_init_timer().
* __TIMER_INITIALIZER() added. It takes @flags and all initializers
are wrappers around it.
* init_timer[_on_stack]_key() now take @flags.
* __init_timer[_on_stack]() added. They take @flags and all init
macros are wrappers around them.
* __setup_timer[_on_stack]() added. It uses __init_timer() and takes
@flags. All setup macros are wrappers around the two.
Note that this patch doesn't add missing init/setup combinations -
e.g. init_timer_deferrable_on_stack(). Adding missing ones is
trivial.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1344449428-24962-4-git-send-email-tj@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
To prepare for addition of another flag, generalize timer->base flags
handling.
* Rename from TBASE_*_FLAG to TIMER_* and make them LU constants.
* Define and use TIMER_FLAG_MASK for flags masking so that multiple
flags can be handled correctly.
* Don't dereference timer->base directly even if
!tbase_get_deferrable(). All two such places are already passed in
@base, so use it instead.
* Make sure tvec_base's alignment is large enough for timer->base
flags using BUILD_BUG_ON().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/1344449428-24962-2-git-send-email-tj@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
On UP try_to_del_timer_sync() is mapped to del_timer() which does not
take the running timer callback into account, so it has different
semantics.
Remove the SMP dependency of try_to_del_timer_sync() by using
base->running_timer in the UP case as well.
[ tglx: Removed set_running_timer() inline and tweaked the changelog ]
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Currently, you have to just define a delayed_work uninitialised, and then
initialise it before first use. That's a tad clumsy. At risk of playing
mind-games with the compiler, fooling it into doing pointer arithmetic
with compile-time-constants, this lets clients properly initialise delayed
work with deferrable timers statically.
This patch was inspired by the issues which lead Artem Bityutskiy to
commit 8eab945c56 ("sunrpc: make the cache cleaner workqueue
deferrable").
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Acked-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
TIMER_INITIALIZER() should initialize the field slack of timer_list as
__init_timer() does.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reorder struct timer_list to remove 8 bytes of alignment padding on 64
bit builds when CONFIG_TIMER_STATS is selected.
timer_list is widely used across the kernel so many structures will
benefit and shrink in size.
For example, with my config on x86_64
per_cpu_dm_data shrinks from 136 to 128 bytes
and
ahci_port_priv shrinks from 1032 to 968 bytes.
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
In some cases (for instance with kernel threads) it may be desireable to
use on-stack deferrable timers to get their power saving benefits. Add
interfaces to support this for the IPS driver.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
While HR timers have had the concept of timer slack for quite some time
now, the legacy timers lacked this concept, and had to make do with
round_jiffies() and friends.
Timer slack is important for power management; grouping timers reduces the
number of wakeups which in turn reduces power consumption.
This patch introduces timer slack to the legacy timers using the following
pieces:
* A slack field in the timer struct
* An api (set_timer_slack) that callers can use to set explicit timer slack
* A default slack of 0.4% of the requested delay for callers that do not set
any explicit slack
* Rounding code that is part of mod_timer() that tries to
group timers around jiffies values every 'power of two'
(so quick timers will group around every 2, but longer timers
will group around every 4, 8, 16, 32 etc)
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: johnstul@us.ibm.com
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Drop prototype for non-existent next_timer_interrupt() function.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: akpm <akpm@linux-foundation.org>
LKML-Reference: <4A9ADEC0.70306@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
When the kernel is configured with CONFIG_TIMER_STATS but timer
stats are runtime disabled we still get calls to
__timer_stats_timer_set_start_info which initializes some
fields in the corresponding struct timer_list.
So add some quick checks in the the timer stats setup functions
to avoid function calls to __timer_stats_timer_set_start_info
when timer stats are disabled.
In an artificial workload that does nothing but playing ping
pong with a single tcp packet via loopback this decreases cpu
consumption by 1 - 1.5%.
This is part of a modified function trace output on SLES11:
perl-2497 [00] 28630647177732388 [+ 125]: sk_reset_timer <-tcp_v4_rcv
perl-2497 [00] 28630647177732513 [+ 125]: mod_timer <-sk_reset_timer
perl-2497 [00] 28630647177732638 [+ 125]: __timer_stats_timer_set_start_info <-mod_timer
perl-2497 [00] 28630647177732763 [+ 125]: __mod_timer <-mod_timer
perl-2497 [00] 28630647177732888 [+ 125]: __timer_stats_timer_set_start_info <-__mod_timer
perl-2497 [00] 28630647177733013 [+ 93]: lock_timer_base <-__mod_timer
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Mustafa Mesanovic <mustafa.mesanovic@de.ibm.com>
Cc: Arjan van de Ven <arjan@infradead.org>
LKML-Reference: <20090623153811.GA4641@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Arun R Bharadwaj <arun@linux.vnet.ibm.com> [2009-04-16 12:11:36]:
This patch creates a new framework for identifying cpu-pinned timers
and hrtimers.
This framework is needed because pinned timers are expected to fire on
the same CPU on which they are queued. So it is essential to identify
these and not migrate them, in case there are any.
For regular timers, the currently existing add_timer_on() can be used
queue pinned timers and subsequently mod_timer_pinned() can be used
to modify the 'expires' field.
For hrtimers, new modes HRTIMER_ABS_PINNED and HRTIMER_REL_PINNED are
added to queue cpu-pinned hrtimer.
[ tglx: use .._PINNED mode argument instead of creating tons of new
functions ]
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Impact: new timer API
Based on an idea from Martin Josefsson with the help of
Patrick McHardy and Stephen Hemminger:
introduce the mod_timer_pending() API which is a mod_timer()
offspring that is an invariant on already removed timers.
(regular mod_timer() re-activates non-pending timers.)
This is useful for the networking code in that it can
allow unserialized mod_timer_pending() timer-forwarding
calls, but a single del_timer*() will stop the timer
from being reactivated again.
Also while at it:
- optimize the regular mod_timer() path some more, the
timer-stat and a debug check was needlessly duplicated
in __mod_timer().
- make the exports come straight after the function, as
most other exports in timer.c already did.
- eliminate __mod_timer() as an external API, change the
users to mod_timer().
The regular mod_timer() code path is not impacted
significantly, due to inlining optimizations and due to
the simplifications.
Based-on-patch-from: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Patrick McHardy <kaber@trash.net>
Cc: netdev@vger.kernel.org
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This modifies the timer code in a way to allow lockdep to detect
deadlocks resulting from a lock being taken in the timer function
as well as around the del_timer_sync() call.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
This patch (as1158b) adds round_jiffies_up() and friends. These
routines work like the analogous round_jiffies() functions, except
that they will never round down.
The new routines will be useful for timeouts where we don't care
exactly when the timer expires, provided it doesn't expire too soon.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Add calls to the generic object debugging infrastructure and provide fixup
functions which allow to keep the system alive when recoverable problems have
been detected by the object debugging core code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
delayed_work_timer_fn() is a timer function, make it static.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Clean up hungarian notation from timer code.
Signed-off-by: Pavel Machek <pavel@suse.cz>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add a flag in /proc/timer_stats to indicate deferrable timers. This will
let developers/users to differentiate between types of tiemrs in
/proc/timer_stats.
Deferrable timer and normal timer will appear in /proc/timer_stats as below.
10D, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
10, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
Also version of timer_stats changes from v0.1 to v0.2
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove the obviously unnecessary includes of <linux/spinlock.h> under the
include/linux/ directory, and fix the couple errors that are introduced as
a result of that.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
get_next_timer_interrupt() returns a delta of (LONG_MAX > 1) in case
there is no timer pending. On 64 bit machines this results in a
multiplication overflow in tick_nohz_stop_sched_tick().
Reported by: Dave Miller <davem@davemloft.net>
Make the return value a constant and limit the return value to a 32 bit
value.
When the max timeout value is returned, we can safely stop the tick
timer device. The max jiffies delta results in a 12 days timeout for
HZ=1000.
In the long term the get_next_timer_interrupt() code needs to be
reworked to return ktime instead of jiffies, but we have to wait until
the last users of the original NO_IDLE_HZ code are converted.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Introduce a new flag for timers - deferrable: Timers that work normally
when system is busy. But, will not cause CPU to come out of idle (just to
service this timer), when CPU is idle. Instead, this timer will be
serviced when CPU eventually wakes up with a subsequent non-deferrable
timer.
The main advantage of this is to avoid unnecessary timer interrupts when
CPU is idle. If the routine currently called by a timer can wait until
next event without any issues, this new timer can be used to setup timer
event for that routine. This, with dynticks, allows CPUs to be lazy,
allowing them to stay in idle for extended period of time by reducing
unnecesary wakeup and thereby reducing the power consumption.
This patch:
Builds this new timer on top of existing timer infrastructure. It uses
last bit in 'base' pointer of timer_list structure to store this deferrable
timer flag. __next_timer_interrupt() function skips over these deferrable
timers when CPU looks for next timer event for which it has to wake up.
This is exported by a new interface init_timer_deferrable() that can be
called in place of regular init_timer().
[akpm@linux-foundation.org: Privatise a #define]
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- hrtimers did not use the hrtimer_restart enum and relied on the implict
int representation. Fix the prototypes and the functions using the enums.
- Use seperate name spaces for the enumerations
- Convert hrtimer_restart macro to inline function
- Add comments
No functional changes.
[akpm@osdl.org: fix input driver]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For CONFIG_NO_HZ we need to calculate the next timer wheel event based on a
given jiffie value. Extend the existing code to allow the extra 'now'
argument. Provide a compability function for the existing implementations to
call the function with now == jiffies. (This also solves the racyness of the
original code vs. jiffies changing during the iteration.)
No functional changes to existing users of this infrastructure.
[ remove WARN_ON() that triggered on s390, by Carsten Otte <cotte@de.ibm.com> ]
[ made new helper static, Adrian Bunk <bunk@stusta.de> ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix a number of kernel-doc entries for header files in include/linux by
making sure they begin with the appropriate '/**' notation and use @var
notation.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Introduce a round_jiffies() function as well as a round_jiffies_relative()
function. These functions round a jiffies value to the next whole second.
The primary purpose of this rounding is to cause all "we don't care exactly
when" timers to happen at the same jiffy.
This avoids multiple timers firing within the second for no real reason;
with dynamic ticks these extra timers cause wakeups from deep sleep CPU
sleep states and thus waste power.
The exact wakeup moment is skewed by the cpu number, to avoid all cpus from
waking up at the exact same time (and hitting the same lock/cachelines
there)
[akpm@osdl.org: fix variable type]
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Commit a4a6198b80:
[PATCH] tvec_bases too large for per-cpu data
introduced "struct tvec_t_base_s boot_tvec_bases" which is visible at
compile time. This means we can kill __init_timer_base and move
timer_base_s's content into tvec_t_base_s.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The nanosleep cleanup allows to remove the data field of hrtimer. The
callback function can use container_of() to get it's own data. Since the
hrtimer structure is anyway embedded in other structures, this adds no
overhead.
Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
