02 Nov, 2017
1 commit
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Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.By default all files without license information are under the default
license of the kernel, which is GPL version 2.Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if
Reviewed-by: Philippe Ombredanne
Reviewed-by: Thomas Gleixner
Signed-off-by: Greg Kroah-Hartman
14 Jan, 2017
1 commit
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In preparation for adding diagnostic checks to catch missing calls to
update_rq_clock(), provide wrappers for (re)pinning and unpinning
rq->lock.Because the pending diagnostic checks allow state to be maintained in
rq_flags across pin contexts, swap the 'struct pin_cookie' arguments
for 'struct rq_flags *'.Signed-off-by: Matt Fleming
Signed-off-by: Peter Zijlstra (Intel)
Cc: Byungchul Park
Cc: Frederic Weisbecker
Cc: Jan Kara
Cc: Linus Torvalds
Cc: Luca Abeni
Cc: Mel Gorman
Cc: Mike Galbraith
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Petr Mladek
Cc: Rik van Riel
Cc: Sergey Senozhatsky
Cc: Thomas Gleixner
Cc: Wanpeng Li
Cc: Yuyang Du
Link: http://lkml.kernel.org/r/20160921133813.31976-5-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar
30 Sep, 2016
1 commit
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select_idle_siblings() is a known pain point for a number of
workloads; it either does too much or not enough and sometimes just
does plain wrong.This rewrite attempts to address a number of issues (but sadly not
all).The current code does an unconditional sched_domain iteration; with
the intent of finding an idle core (on SMT hardware). The problems
which this patch tries to address are:- its pointless to look for idle cores if the machine is real busy;
at which point you're just wasting cycles.- it's behaviour is inconsistent between SMT and !SMT hardware in
that !SMT hardware ends up doing a scan for any idle CPU in the LLC
domain, while SMT hardware does a scan for idle cores and if that
fails, falls back to a scan for idle threads on the 'target' core.The new code replaces the sched_domain scan with 3 explicit scans:
1) search for an idle core in the LLC
2) search for an idle CPU in the LLC
3) search for an idle thread in the 'target' corewhere 1 and 3 are conditional on SMT support and 1 and 2 have runtime
heuristics to skip the step.Step 1) is conditional on sd_llc_shared->has_idle_cores; when a cpu
goes idle and sd_llc_shared->has_idle_cores is false, we scan all SMT
siblings of the CPU going idle. Similarly, we clear
sd_llc_shared->has_idle_cores when we fail to find an idle core.Step 2) tracks the average cost of the scan and compares this to the
average idle time guestimate for the CPU doing the wakeup. There is a
significant fudge factor involved to deal with the variability of the
averages. Esp. hackbench was sensitive to this.Step 3) is unconditional; we assume (also per step 1) that scanning
all SMT siblings in a core is 'cheap'.With this; SMT systems gain step 2, which cures a few benchmarks --
notably one from Facebook.One 'feature' of the sched_domain iteration, which we preserve in the
new code, is that it would start scanning from the 'target' CPU,
instead of scanning the cpumask in cpu id order. This avoids multiple
CPUs in the LLC scanning for idle to gang up and find the same CPU
quite as much. The down side is that tasks can end up hopping across
the LLC for no apparent reason.Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar
05 Sep, 2016
1 commit
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The schedstat_*() macros are inconsistent: most of them take a pointer
and a field which the macro combines, whereas schedstat_set() takes the
already combined ptr->field.The already combined ptr->field argument is actually more intuitive and
easier to use, and there's no reason to require the user to split the
variable up, so convert the macros to use the combined argument.Signed-off-by: Josh Poimboeuf
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Matt Fleming
Cc: Mel Gorman
Cc: Peter Zijlstra
Cc: Srikar Dronamraju
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/54953ca25bb579f3a5946432dee409b0e05222c6.1466184592.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
05 May, 2016
1 commit
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The problem with the existing lock pinning is that each pin is of
value 1; this mean you can simply unpin if you know its pinned,
without having any extra information.This scheme generates a random (16 bit) cookie for each pin and
requires this same cookie to unpin. This means you have to keep the
cookie in context.No objsize difference for !LOCKDEP kernels.
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar
23 Nov, 2015
1 commit
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Commit cd126afe838d ("sched/fair: Remove rq's runnable avg") got rid of
rq->avg and so there is no need to update it any more when entering or
exiting idle.Remove the now empty functions idle_{enter|exit}_fair().
Signed-off-by: Dietmar Eggemann
Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: Yuyang Du
Link: http://lkml.kernel.org/r/1445342681-17171-1-git-send-email-dietmar.eggemann@arm.com
Signed-off-by: Ingo Molnar
12 Aug, 2015
1 commit
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Give every class a set_cpus_allowed() method, this enables some small
optimization in the RT,DL implementation by avoiding a double
cpumask_weight() call.Signed-off-by: Peter Zijlstra (Intel)
Cc: Linus Torvalds
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: dedekind1@gmail.com
Cc: juri.lelli@arm.com
Cc: mgorman@suse.de
Cc: riel@redhat.com
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/20150515154833.614517487@infradead.org
Signed-off-by: Ingo Molnar
24 Nov, 2014
1 commit
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Chris bisected a NULL pointer deference in task_sched_runtime() to
commit 6e998916dfe3 'sched/cputime: Fix clock_nanosleep()/clock_gettime()
inconsistency'.Chris observed crashes in atop or other /proc walking programs when he
started fork bombs on his machine. He assumed that this is a new exit
race, but that does not make any sense when looking at that commit.What's interesting is that, the commit provides update_curr callbacks
for all scheduling classes except stop_task and idle_task.While nothing can ever hit that via the clock_nanosleep() and
clock_gettime() interfaces, which have been the target of the commit in
question, the author obviously forgot that there are other code paths
which invoke task_sched_runtime()do_task_stat(()
thread_group_cputime_adjusted()
thread_group_cputime()
task_cputime()
task_sched_runtime()
if (task_current(rq, p) && task_on_rq_queued(p)) {
update_rq_clock(rq);
up->sched_class->update_curr(rq);
}If the stats are read for a stomp machine task, aka 'migration/N' and
that task is current on its cpu, this will happily call the NULL pointer
of stop_task->update_curr. Ooops.Chris observation that this happens faster when he runs the fork bomb
makes sense as the fork bomb will kick migration threads more often so
the probability to hit the issue will increase.Add the missing update_curr callbacks to the scheduler classes stop_task
and idle_task. While idle tasks cannot be monitored via /proc we have
other means to hit the idle case.Fixes: 6e998916dfe3 'sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency'
Reported-by: Chris Mason
Reported-and-tested-by: Borislav Petkov
Signed-off-by: Thomas Gleixner
Cc: Ingo Molnar
Cc: Stanislaw Gruszka
Cc: Peter Zijlstra
Signed-off-by: Linus Torvalds
16 Jul, 2014
1 commit
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We always use resched_task() with rq->curr argument.
It's not possible to reschedule any task but rq's current.The patch introduces resched_curr(struct rq *) to
replace all of the repeating patterns. The main aim
is cleanup, but there is a little size profit too:(before)
$ size kernel/sched/built-in.o
text data bss dec hex filename
155274 16445 7042 178761 2ba49 kernel/sched/built-in.o$ size vmlinux
text data bss dec hex filename
7411490 1178376 991232 9581098 92322a vmlinux(after)
$ size kernel/sched/built-in.o
text data bss dec hex filename
155130 16445 7042 178617 2b9b9 kernel/sched/built-in.o$ size vmlinux
text data bss dec hex filename
7411362 1178376 991232 9580970 9231aa vmlinuxI was choosing between resched_curr() and resched_rq(),
and the first name looks better for me.A little lie in Documentation/trace/ftrace.txt. I have not
actually collected the tracing again. With a hope the patch
won't make execution times much worse :)Signed-off-by: Kirill Tkhai
Signed-off-by: Peter Zijlstra
Cc: Linus Torvalds
Cc: Randy Dunlap
Cc: Steven Rostedt
Link: http://lkml.kernel.org/r/20140628200219.1778.18735.stgit@localhost
Signed-off-by: Ingo Molnar
11 Mar, 2014
1 commit
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We close idle_exit_fair() bracket in case of we've pulled something or we've received
task of high priority class.Signed-off-by: Kirill Tkhai
Signed-off-by: Peter Zijlstra
Cc: Vincent Guittot
Link: http://lkml.kernel.org/r/1394098315.19290.10.camel@tkhai
Signed-off-by: Ingo Molnar
22 Feb, 2014
2 commits
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Remove a few gratuitous #ifdefs in pick_next_task*().
Cc: Ingo Molnar
Cc: Steven Rostedt
Cc: Juri Lelli
Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/n/tip-nnzddp5c4fijyzzxxrwlxghf@git.kernel.org
Signed-off-by: Thomas Gleixner -
Dan Carpenter reported:
> kernel/sched/rt.c:1347 pick_next_task_rt() warn: variable dereferenced before check 'prev' (see line 1338)
> kernel/sched/deadline.c:1011 pick_next_task_dl() warn: variable dereferenced before check 'prev' (see line 1005)Kirill also spotted that migrate_tasks() will have an instant NULL
deref because pick_next_task() will immediately deref prev.Instead of fixing all the corner cases because migrate_tasks() can
pass in a NULL prev task in the unlikely case of hot-un-plug, provide
a fake task such that we can remove all the NULL checks from the far
more common paths.A further problem; not previously spotted; is that because we pushed
pre_schedule() and idle_balance() into pick_next_task() we now need to
avoid those getting called and pulling more tasks on our dying CPU.We avoid pull_{dl,rt}_task() by setting fake_task.prio to MAX_PRIO+1.
We also note that since we call pick_next_task() exactly the amount of
times we have runnable tasks present, we should never land in
idle_balance().Fixes: 38033c37faab ("sched: Push down pre_schedule() and idle_balance()")
Cc: Juri Lelli
Cc: Ingo Molnar
Cc: Steven Rostedt
Reported-by: Kirill Tkhai
Reported-by: Dan Carpenter
Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/r/20140212094930.GB3545@laptop.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner
11 Feb, 2014
1 commit
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This patch both merged idle_balance() and pre_schedule() and pushes
both of them into pick_next_task().Conceptually pre_schedule() and idle_balance() are rather similar,
both are used to pull more work onto the current CPU.We cannot however first move idle_balance() into pre_schedule_fair()
since there is no guarantee the last runnable task is a fair task, and
thus we would miss newidle balances.Similarly, the dl and rt pre_schedule calls must be ran before
idle_balance() since their respective tasks have higher priority and
it would not do to delay their execution searching for less important
tasks first.However, by noticing that pick_next_tasks() already traverses the
sched_class hierarchy in the right order, we can get the right
behaviour and do away with both calls.We must however change the special case optimization to also require
that prev is of sched_class_fair, otherwise we can miss doing a dl or
rt pull where we needed one.Signed-off-by: Peter Zijlstra
Cc: Linus Torvalds
Cc: Andrew Morton
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/n/tip-a8k6vvaebtn64nie345kx1je@git.kernel.org
Signed-off-by: Ingo Molnar
10 Feb, 2014
2 commits
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The idle post_schedule flag is just a vile waste of time, furthermore
it appears unneeded, move the idle_enter_fair() call into
pick_next_task_idle().Signed-off-by: Peter Zijlstra
Cc: Daniel Lezcano
Cc: Vincent Guittot
Cc: alex.shi@linaro.org
Cc: mingo@kernel.org
Cc: Steven Rostedt
Link: http://lkml.kernel.org/n/tip-aljykihtxJt3mkokxi0qZurb@git.kernel.org
Signed-off-by: Ingo Molnar -
In order to avoid having to do put/set on a whole cgroup hierarchy
when we context switch, push the put into pick_next_task() so that
both operations are in the same function. Further changes then allow
us to possibly optimize away redundant work.Signed-off-by: Peter Zijlstra
Link: http://lkml.kernel.org/r/1328936700.2476.17.camel@laptop
Signed-off-by: Ingo Molnar
09 Oct, 2013
1 commit
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Use the new stop_two_cpus() to implement migrate_swap(), a function that
flips two tasks between their respective cpus.I'm fairly sure there's a less crude way than employing the stop_two_cpus()
method, but everything I tried either got horribly fragile and/or complex. So
keep it simple for now.The notable detail is how we 'migrate' tasks that aren't runnable
anymore. We'll make it appear like we migrated them before they went to
sleep. The sole difference is the previous cpu in the wakeup path, so we
override this.Signed-off-by: Peter Zijlstra
Reviewed-by: Rik van Riel
Cc: Andrea Arcangeli
Cc: Johannes Weiner
Cc: Srikar Dronamraju
Signed-off-by: Mel Gorman
Link: http://lkml.kernel.org/r/1381141781-10992-39-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar
04 May, 2013
1 commit
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The scheduler doesn't yet fully support environments
with a single task running without a periodic tick.In order to ensure we still maintain the duties of scheduler_tick(),
keep at least 1 tick per second.This makes sure that we keep the progression of various scheduler
accounting and background maintainance even with a very low granularity.
Examples include cpu load, sched average, CFS entity vruntime,
avenrun and events such as load balancing, amongst other details
handled in sched_class::task_tick().This limitation will be removed in the future once we get
these individual items to work in full dynticks CPUs.Suggested-by: Ingo Molnar
Signed-off-by: Frederic Weisbecker
Cc: Christoph Lameter
Cc: Hakan Akkan
Cc: Ingo Molnar
Cc: Kevin Hilman
Cc: Li Zhong
Cc: Paul E. McKenney
Cc: Paul Gortmaker
Cc: Peter Zijlstra
Cc: Steven Rostedt
Cc: Thomas Gleixner
21 Apr, 2013
1 commit
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The current update of the rq's load can be erroneous when RT
tasks are involved.The update of the load of a rq that becomes idle, is done only
if the avg_idle is less than sysctl_sched_migration_cost. If RT
tasks and short idle duration alternate, the runnable_avg will
not be updated correctly and the time will be accounted as idle
time when a CFS task wakes up.A new idle_enter function is called when the next task is the
idle function so the elapsed time will be accounted as run time
in the load of the rq, whatever the average idle time is. The
function update_rq_runnable_avg is removed from idle_balance.When a RT task is scheduled on an idle CPU, the update of the
rq's load is not done when the rq exit idle state because CFS's
functions are not called. Then, the idle_balance, which is
called just before entering the idle function, updates the rq's
load and makes the assumption that the elapsed time since the
last update, was only running time.As a consequence, the rq's load of a CPU that only runs a
periodic RT task, is close to LOAD_AVG_MAX whatever the running
duration of the RT task is.A new idle_exit function is called when the prev task is the
idle function so the elapsed time will be accounted as idle time
in the rq's load.Signed-off-by: Vincent Guittot
Acked-by: Peter Zijlstra
Acked-by: Steven Rostedt
Cc: linaro-kernel@lists.linaro.org
Cc: peterz@infradead.org
Cc: pjt@google.com
Cc: fweisbec@gmail.com
Cc: efault@gmx.de
Link: http://lkml.kernel.org/r/1366302867-5055-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar
06 Jul, 2012
1 commit
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Thanks to Charles Wang for spotting the defects in the current code:
- If we go idle during the sample window -- after sampling, we get a
negative bias because we can negate our own sample.- If we wake up during the sample window we get a positive bias
because we push the sample to a known active period.So rewrite the entire nohz load-avg muck once again, now adding
copious documentation to the code.Reported-and-tested-by: Doug Smythies
Reported-and-tested-by: Charles Wang
Signed-off-by: Peter Zijlstra
Cc: Linus Torvalds
Cc: Andrew Morton
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1340373782.18025.74.camel@twins
[ minor edits ]
Signed-off-by: Ingo Molnar
07 May, 2012
1 commit
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Change sched_*.c to sched/*.c in documentation and comments.
Signed-off-by: Hiroshi Shimamoto
Cc: Peter Zijlstra
Link: http://lkml.kernel.org/r/4F795CAC.9080206@ct.jp.nec.com
Signed-off-by: Ingo Molnar
17 Nov, 2011
1 commit
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There's too many sched*.[ch] files in kernel/, give them their own
directory.(No code changed, other than Makefile glue added.)
Signed-off-by: Peter Zijlstra
Signed-off-by: Ingo Molnar