linux-toradex.git/kernel/sched_debug.c, branch v3.2.73

sched: Fix possible divide by zero in avg_atom() calculation

2014-08-06T17:07:38+00:00

commit b0ab99e7736af88b8ac1b7ae50ea287fffa2badc upstream.

proc_sched_show_task() does:

  if (nr_switches)
	do_div(avg_atom, nr_switches);

nr_switches is unsigned long and do_div truncates it to 32 bits, which
means it can test non-zero on e.g. x86-64 and be truncated to zero for
division.

Fix the problem by using div64_ul() instead.

As a side effect calculations of avg_atom for big nr_switches are now correct.

Signed-off-by: Mateusz Guzik 
Signed-off-by: Peter Zijlstra 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1402750809-31991-1-git-send-email-mguzik@redhat.com
Signed-off-by: Ingo Molnar 
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings

sched: Avoid throttle_cfs_rq() racing with period_timer stopping

2014-01-03T04:33:31+00:00

commit f9f9ffc237dd924f048204e8799da74f9ecf40cf upstream.

throttle_cfs_rq() doesn't check to make sure that period_timer is running,
and while update_curr/assign_cfs_runtime does, a concurrently running
period_timer on another cpu could cancel itself between this cpu's
update_curr and throttle_cfs_rq(). If there are no other cfs_rqs running
in the tg to restart the timer, this causes the cfs_rq to be stranded
forever.

Fix this by calling __start_cfs_bandwidth() in throttle if the timer is
inactive.

(Also add some sched_debug lines for cfs_bandwidth.)

Tested: make a run/sleep task in a cgroup, loop switching the cgroup
between 1ms/100ms quota and unlimited, checking for timer_active=0 and
throttled=1 as a failure. With the throttle_cfs_rq() change commented out
this fails, with the full patch it passes.

Signed-off-by: Ben Segall 
Signed-off-by: Peter Zijlstra 
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181632.22647.84174.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar 
[bwh: Backported to 3.2: adjust filenames]
Signed-off-by: Ben Hutchings

sched: Get rid of lock_depth

2011-04-24T11:18:38+00:00

Neil Brown pointed out that lock_depth somehow escaped the BKL
removal work.  Let's get rid of it now.

Note that the perf scripting utilities still have a bunch of
code for dealing with common_lock_depth in tracepoints; I have
left that in place in case anybody wants to use that code with
older kernels.

Suggested-by: Neil Brown 
Signed-off-by: Jonathan Corbet 
Cc: Arnd Bergmann 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Link: http://lkml.kernel.org/r/20110422111910.456c0e84@bike.lwn.net
Signed-off-by: Ingo Molnar

sched: Provide p->on_rq

2011-04-14T06:52:35+00:00

Provide a generic p->on_rq because the p->se.on_rq semantics are
unfavourable for lockless wakeups but needed for sched_fair.

In particular, p->on_rq is only cleared when we actually dequeue the
task in schedule() and not on any random dequeue as done by things
like __migrate_task() and __sched_setscheduler().

This also allows us to remove p->se usage from !sched_fair code.

Reviewed-by: Frank Rowand 
Cc: Mike Galbraith 
Cc: Nick Piggin 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Signed-off-by: Ingo Molnar 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20110405152728.949545047@chello.nl

sched: Use a buddy to implement yield_task_fair()

2011-02-03T13:20:33+00:00

Use the buddy mechanism to implement yield_task_fair.  This
allows us to skip onto the next highest priority se at every
level in the CFS tree, unless doing so would introduce gross
unfairness in CPU time distribution.

We order the buddy selection in pick_next_entity to check
yield first, then last, then next.  We need next to be able
to override yield, because it is possible for the "next" and
"yield" task to be different processen in the same sub-tree
of the CFS tree.  When they are, we need to go into that
sub-tree regardless of the "yield" hint, and pick the correct
entity once we get to the right level.

Signed-off-by: Rik van Riel 
Signed-off-by: Peter Zijlstra 
LKML-Reference: <20110201095103.3a79e92a@annuminas.surriel.com>
Signed-off-by: Ingo Molnar

sched: Replace rq->bkl_count with rq->rq_sched_info.bkl_count

2011-01-18T14:09:43+00:00

Now rq->rq_sched_info.bkl_count is not used for rq, scroll
rq->bkl_count into it. Thus we can save some space for rq.

Signed-off-by: Yong Zhang 
Signed-off-by: Peter Zijlstra 
LKML-Reference: <1294991859-13246-1-git-send-email-yong.zhang0@gmail.com>
Signed-off-by: Ingo Molnar

sched: Display autogroup names in /proc/sched_debug

2011-01-18T14:09:40+00:00

Add autogroup name to cfs_rq and tasks information to /proc/sched_debug.

Signed-off-by: Bharata B Rao 
Signed-off-by: Peter Zijlstra 
LKML-Reference: <20110111101257.GF4772@in.ibm.com>
Signed-off-by: Ingo Molnar

sched: Reinstate group names in /proc/sched_debug

2011-01-18T14:09:39+00:00

Displaying of group names in /proc/sched_debug was dropped in autogroup
patches. Add group names while displaying cfs_rq and tasks information.

Signed-off-by: Bharata B Rao 
Signed-off-by: Peter Zijlstra 
LKML-Reference: <20110111101153.GE4772@in.ibm.com>
Signed-off-by: Ingo Molnar

sched: Add 'autogroup' scheduling feature: automated per session task groups

2010-11-30T15:03:35+00:00

A recurring complaint from CFS users is that parallel kbuild has
a negative impact on desktop interactivity.  This patch
implements an idea from Linus, to automatically create task
groups.  Currently, only per session autogroups are implemented,
but the patch leaves the way open for enhancement.

Implementation: each task's signal struct contains an inherited
pointer to a refcounted autogroup struct containing a task group
pointer, the default for all tasks pointing to the
init_task_group.  When a task calls setsid(), a new task group
is created, the process is moved into the new task group, and a
reference to the preveious task group is dropped.  Child
processes inherit this task group thereafter, and increase it's
refcount.  When the last thread of a process exits, the
process's reference is dropped, such that when the last process
referencing an autogroup exits, the autogroup is destroyed.

At runqueue selection time, IFF a task has no cgroup assignment,
its current autogroup is used.

Autogroup bandwidth is controllable via setting it's nice level
through the proc filesystem:

  cat /proc//autogroup

Displays the task's group and the group's nice level.

  echo  > /proc//autogroup

Sets the task group's shares to the weight of nice  task.
Setting nice level is rate limited for !admin users due to the
abuse risk of task group locking.

The feature is enabled from boot by default if
CONFIG_SCHED_AUTOGROUP=y is selected, but can be disabled via
the boot option noautogroup, and can also be turned on/off on
the fly via:

  echo [01] > /proc/sys/kernel/sched_autogroup_enabled

... which will automatically move tasks to/from the root task group.

Signed-off-by: Mike Galbraith 
Acked-by: Linus Torvalds 
Acked-by: Peter Zijlstra 
Cc: Markus Trippelsdorf 
Cc: Mathieu Desnoyers 
Cc: Paul Turner 
Cc: Oleg Nesterov 
[ Removed the task_group_path() debug code, and fixed !EVENTFD build failure. ]
Signed-off-by: Ingo Molnar 
LKML-Reference: <1290281700.28711.9.camel@maggy.simson.net>
Signed-off-by: Ingo Molnar

sched: Add some clock info to sched_debug

2010-11-23T09:29:08+00:00

Add more clock information to /proc/sched_debug, Thomas wanted to see
the sched_clock_stable state.

Requested-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra 
LKML-Reference: 
Signed-off-by: Ingo Molnar