linux-toradex.git/include/linux/hardirq.h, branch v4.6-rc3

sched/preempt: Merge preempt_mask.h into preempt.h

2015-05-19T06:39:11+00:00

preempt_mask.h defines all the preempt_count semantics and related
symbols: preempt, softirq, hardirq, nmi, preempt active, need resched,
etc...

preempt.h defines the accessors and mutators of preempt_count.

But there is a messy dependency game around those two header files:

	* preempt_mask.h includes preempt.h in order to access preempt_count()

	* preempt_mask.h defines all preempt_count semantic and symbols
	  except PREEMPT_NEED_RESCHED that is needed by asm/preempt.h
	  Thus we need to define it from preempt.h, right before including
	  asm/preempt.h, instead of defining it to preempt_mask.h with the
	  other preempt_count symbols. Therefore the preempt_count semantics
	  happen to be spread out.

	* We plan to introduce preempt_active_[enter,exit]() to consolidate
	  preempt_schedule*() code. But we'll need to access both preempt_count
	  mutators (preempt_count_add()) and preempt_count symbols
	  (PREEMPT_ACTIVE, PREEMPT_OFFSET). The usual place to define preempt
	  operations is in preempt.h but then we'll need symbols in
	  preempt_mask.h which already includes preempt.h. So we end up with
	  a ressource circle dependency.

Lets merge preempt_mask.h into preempt.h to solve these dependency issues.
This way we gather semantic symbols and operation definition of
preempt_count in a single file.

This is a dumb copy-paste merge. Further merge re-arrangments are
performed in a subsequent patch to ease review.

Signed-off-by: Frederic Weisbecker 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1431441711-29753-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

genirq: Provide disable_hardirq()

2015-02-18T14:08:33+00:00

For things like netpoll there is a need to disable an interrupt from
atomic context. Currently netpoll uses disable_irq() which will
sleep-wait on threaded handlers and thus forced_irqthreads breaks
things.

Provide disable_hardirq(), which uses synchronize_hardirq() to only wait
for active hardirq handlers; also change synchronize_hardirq() to
return the status of threaded handlers.

This will allow one to try-disable an interrupt from atomic context, or
in case of request_threaded_irq() to only wait for the hardirq part.

Suggested-by: Sabrina Dubroca 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Arnd Bergmann 
Cc: David Miller 
Cc: Eyal Perry 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Quentin Lambert 
Cc: Randy Dunlap 
Cc: Russell King 
Link: http://lkml.kernel.org/r/20150205130623.GH5029@twins.programming.kicks-ass.net
[ Fixed typos and such. ]
Signed-off-by: Ingo Molnar

genirq: Provide synchronize_hardirq()

2014-02-19T16:22:44+00:00

synchronize_irq() waits for hard irq and threaded handlers to complete
before returning. For some special cases we only need to make sure
that the hard interrupt part of the irq line is not in progress when
we disabled the - possibly shared - interrupt at the device level.

A proper use case for this was provided by Russell. The sdhci driver
requires some irq triggered functions to be run in thread context. The
current implementation of the thread context is a sdio private kthread
construct, which has quite some shortcomings. These can be avoided
when the thread is directly associated to the device interrupt via the
generic threaded irq infrastructure.

Though there is a corner case related to run time power management
where one side disables the device interrupts at the device level and
needs to make sure, that an already running hard interrupt handler has
completed before proceeding further. Though that hard interrupt
handler might wake the associated thread, which in turn can request
the runtime PM to reenable the device. Using synchronize_irq() leads
to an immediate deadlock of the irq thread waiting for the PM lock and
the synchronize_irq() waiting for the irq thread to complete.

Due to the fact that it is sufficient for this case to ensure that no
hard irq handler is executing a new function which avoids the check
for the thread is required.

Add a function, which just monitors the hard irq parts and ignores the
threaded handlers.

Signed-off-by: Thomas Gleixner 
Tested-by: Russell King 
Cc: Chris Ball 
Acked-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20140215003823.653236081@linutronix.de

sched/preempt, locking: Rework local_bh_{dis,en}able()

2014-01-13T16:32:27+00:00

Currently local_bh_disable() is out-of-line for no apparent reason.
So inline it to save a few cycles on call/return nonsense, the
function body is a single add on x86 (a few loads and store extra on
load/store archs).

Also expose two new local_bh functions:

  __local_bh_{dis,en}able_ip(unsigned long ip, unsigned int cnt);

Which implement the actual local_bh_{dis,en}able() behaviour.

The next patch uses the exposed @cnt argument to optimize bh lock
functions.

With build fixes from Jacob Pan.

Cc: rjw@rjwysocki.net
Cc: rui.zhang@intel.com
Cc: jacob.jun.pan@linux.intel.com
Cc: Mike Galbraith 
Cc: hpa@zytor.com
Cc: Arjan van de Ven 
Cc: lenb@kernel.org
Reviewed-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar

sched: Extract the basic add/sub preempt_count modifiers

2013-09-25T12:07:54+00:00

Rewrite the preempt_count macros in order to extract the 3 basic
preempt_count value modifiers:

  __preempt_count_add()
  __preempt_count_sub()

and the new:

  __preempt_count_dec_and_test()

And since we're at it anyway, replace the unconventional
$op_preempt_count names with the more conventional preempt_count_$op.

Since these basic operators are equivalent to the previous _notrace()
variants, do away with the _notrace() versions.

Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/n/tip-ewbpdbupy9xpsjhg960zwbv8@git.kernel.org
Signed-off-by: Ingo Molnar

Remove GENERIC_HARDIRQ config option

2013-09-13T13:09:52+00:00

After the last architecture switched to generic hard irqs the config
options HAVE_GENERIC_HARDIRQS & GENERIC_HARDIRQS and the related code
for !CONFIG_GENERIC_HARDIRQS can be removed.

Signed-off-by: Martin Schwidefsky

hardirq: Split preempt count mask definitions

2013-08-14T15:14:52+00:00

In order to use static keys with vtime APIs, we'll need to
add static keys headers to vtime.h

hardirq.h then becomes a problem because it needs vtime.h
for irqtime accounting in irq_enter/irq_exit, but it's
often included just to get the irq mask definitions in the
task preempt_count field and the APIs that come along:
in_interrupt(), in_hardirq(), etc...

Some very low level arch headers sometimes need these masks
and APIs such as arch/m68k/include/asm/irqflags.h for example.
But they don't want to include hardirq.h if vtime.h, jump_label.h
and even workqueue.h come along. Including such bloated high
level header from arch headers can quickly result in circular
headers dependency that crash the build.

So let's split hardirq.h in two parts:

* preempt_mask.h that gathers all the preempt_count definitions
and the APIs associated. This one is considered low level and can
be safely included anywhere.

* hardirq.h that includes the previous one. It defines the irq
entry/exit APIs.

To avoid future circular headers dependencies, the preempt_mask.h
inclusion can replace hardirq.h on files that don't implement irq
low level handlers but just need the atomic/context check APIs.

Signed-off-by: Frederic Weisbecker 
Cc: Steven Rostedt 
Cc: Paul E. McKenney 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Borislav Petkov 
Cc: Li Zhong 
Cc: Mike Galbraith 
Cc: Kevin Hilman

rcu: Remove TINY_PREEMPT_RCU

2013-06-10T20:45:49+00:00

TINY_PREEMPT_RCU adds significant code and complexity, but does not
offer commensurate benefits.  People currently using TINY_PREEMPT_RCU
can get much better memory footprint with TINY_RCU, or, if they really
need preemptible RCU, they can use TREE_PREEMPT_RCU with a relatively
minor degradation in memory footprint.  Please note that this move
has been widely publicized on LKML (https://lkml.org/lkml/2012/11/12/545)
and on LWN (http://lwn.net/Articles/541037/).

This commit therefore removes TINY_PREEMPT_RCU.

Signed-off-by: Paul E. McKenney 
[ paulmck: Updated to eliminate #else in rcutiny.h as suggested by Josh ]
Reviewed-by: Josh Triplett

irq: Remove IRQ_EXIT_OFFSET workaround

2013-02-21T23:05:07+00:00

The IRQ_EXIT_OFFSET trick was used to make sure the irq
doesn't get preempted after we substract the HARDIRQ_OFFSET
until we are entirely done with any code in irq_exit().

This workaround was necessary because some archs may call
irq_exit() with irqs enabled and there is still some code
in the end of this function that is not covered by the
HARDIRQ_OFFSET but want to stay non-preemptible.

Now that irq are always disabled in irq_exit(), the whole code
is guaranteed not to be preempted. We can thus remove this hack.

Signed-off-by: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Paul E. McKenney

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2013-02-20T02:19:48+00:00

Pull scheduler changes from Ingo Molnar:
 "Main changes:

   - scheduler side full-dynticks (user-space execution is undisturbed
     and receives no timer IRQs) preparation changes that convert the
     cputime accounting code to be full-dynticks ready, from Frederic
     Weisbecker.

   - Initial sched.h split-up changes, by Clark Williams

   - select_idle_sibling() performance improvement by Mike Galbraith:

        " 1 tbench pair (worst case) in a 10 core + SMT package:

          pre   15.22 MB/sec 1 procs
          post 252.01 MB/sec 1 procs "

  - sched_rr_get_interval() ABI fix/change.  We think this detail is not
    used by apps (so it's not an ABI in practice), but lets keep it
    under observation.

  - misc RT scheduling cleanups, optimizations"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  sched/rt: Add  header to 
  cputime: Remove irqsave from seqlock readers
  sched, powerpc: Fix sched.h split-up build failure
  cputime: Restore CPU_ACCOUNTING config defaults for PPC64
  sched/rt: Move rt specific bits into new header file
  sched/rt: Add a tuning knob to allow changing SCHED_RR timeslice
  sched: Move sched.h sysctl bits into separate header
  sched: Fix signedness bug in yield_to()
  sched: Fix select_idle_sibling() bouncing cow syndrome
  sched/rt: Further simplify pick_rt_task()
  sched/rt: Do not account zero delta_exec in update_curr_rt()
  cputime: Safely read cputime of full dynticks CPUs
  kvm: Prepare to add generic guest entry/exit callbacks
  cputime: Use accessors to read task cputime stats
  cputime: Allow dynamic switch between tick/virtual based cputime accounting
  cputime: Generic on-demand virtual cputime accounting
  cputime: Move default nsecs_to_cputime() to jiffies based cputime file
  cputime: Librarize per nsecs resolution cputime definitions
  cputime: Avoid multiplication overflow on utime scaling
  context_tracking: Export context state for generic vtime
  ...

Fix up conflict in kernel/context_tracking.c due to comment additions.