linux.git/kernel/irq/manage.c, branch v3.14

genirq: Remove racy waitqueue_active check

2014-02-27T09:54:16+00:00

We hit one rare case below:

T1 calling disable_irq(), but hanging at synchronize_irq()
always;
The corresponding irq thread is in sleeping state;
And all CPUs are in idle state;

After analysis, we found there is one possible scenerio which
causes T1 is waiting there forever:
CPU0                                       CPU1
 synchronize_irq()
  wait_event()
    spin_lock()
                                           atomic_dec_and_test(&threads_active)
      insert the __wait into queue
    spin_unlock()
                                           if(waitqueue_active)
    atomic_read(&threads_active)
                                             wake_up()

Here after inserted the __wait into queue on CPU0, and before
test if queue is empty on CPU1, there is no barrier, it maybe
cause it is not visible for CPU1 immediately, although CPU0 has
updated the queue list.
It is similar for CPU0 atomic_read() threads_active also.

So we'd need one smp_mb() before waitqueue_active.that, but removing
the waitqueue_active() check solves it as wel l and it makes
things simple and clear.

Signed-off-by: Chuansheng Liu 
Cc: Xiaoming Wang 
Link: http://lkml.kernel.org/r/1393212590-32543-1-git-send-email-chuansheng.liu@intel.com
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial

2013-11-16T00:47:22+00:00

Pull trivial tree updates from Jiri Kosina:
 "Usual earth-shaking, news-breaking, rocket science pile from
  trivial.git"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (23 commits)
  doc: usb: Fix typo in Documentation/usb/gadget_configs.txt
  doc: add missing files to timers/00-INDEX
  timekeeping: Fix some trivial typos in comments
  mm: Fix some trivial typos in comments
  irq: Fix some trivial typos in comments
  NUMA: fix typos in Kconfig help text
  mm: update 00-INDEX
  doc: Documentation/DMA-attributes.txt fix typo
  DRM: comment: `halve' -> `half'
  Docs: Kconfig: `devlopers' -> `developers'
  doc: typo on word accounting in kprobes.c in mutliple architectures
  treewide: fix "usefull" typo
  treewide: fix "distingush" typo
  mm/Kconfig: Grammar s/an/a/
  kexec: Typo s/the/then/
  Documentation/kvm: Update cpuid documentation for steal time and pv eoi
  treewide: Fix common typo in "identify"
  __page_to_pfn: Fix typo in comment
  Correct some typos for word frequency
  clk: fixed-factor: Fix a trivial typo
  ...

genirq: Set the irq thread policy without checking CAP_SYS_NICE

2013-10-28T08:50:42+00:00

In commit ee23871389 ("genirq: Set irq thread to RT priority on
creation") we moved the assigment of the thread's priority from the
thread's function into __setup_irq(). That function may run in user
context for instance if the user opens an UART node and then driver
calls requests in the ->open() callback. That user may not have
CAP_SYS_NICE and so the irq thread won't run with the SCHED_OTHER
policy.

This patch uses sched_setscheduler_nocheck() so we omit the CAP_SYS_NICE
check which is otherwise required for the SCHED_OTHER policy.

[bigeasy: Rewrite the changelog]

Signed-off-by: Thomas Pfaff 
Cc: Ivo Sieben 
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1381489240-29626-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Thomas Gleixner

irq: Fix some trivial typos in comments

2013-10-18T12:49:30+00:00

Signed-off-by: Xie XiuQi 
[jkosina@suse.cz: fix 'explicitly', noticed by Randy Dunlap]
Signed-off-by: Jiri Kosina

genirq: Fix can_request_irq() for IRQs without an action

2013-06-28T10:56:03+00:00

Commit 02725e7471b8 ('genirq: Use irq_get/put functions'),
inadvertently changed can_request_irq() to return 0 for IRQs that have
no action.  This causes pcibios_lookup_irq() to select only IRQs that
already have an action with IRQF_SHARED set, or to fail if there are
none.  Change can_request_irq() to return 1 for IRQs that have no
action (if the first two conditions are met).

Reported-by: Bjarni Ingi Gislason 
Tested-by: Bjarni Ingi Gislason  (against 3.2)
Signed-off-by: Ben Hutchings 
Cc: 709647@bugs.debian.org
Cc: stable@vger.kernel.org # 2.6.39+
Link: http://bugs.debian.org/709647
Link: http://lkml.kernel.org/r/1372383630.23847.40.camel@deadeye.wl.decadent.org.uk
Signed-off-by: Thomas Gleixner

genirq: Set irq thread to RT priority on creation

2013-06-11T14:18:50+00:00

When a threaded irq handler is installed the irq thread is initially
created on normal scheduling priority. Only after the irq thread is
woken up it sets its priority to RT_FIFO MAX_USER_RT_PRIO/2 itself.

This means that interrupts that occur directly after the irq handler
is installed will be handled on a normal scheduling priority instead
of the realtime priority that one would expect.

Fix this by setting the RT priority on creation of the irq_thread.

Signed-off-by: Ivo Sieben 
Cc: Sebastian Andrzej Siewior  
Cc: Steven Rostedt 
Link: http://lkml.kernel.org/r/1370254322-17240-1-git-send-email-meltedpianoman@gmail.com
Signed-off-by: Thomas Gleixner

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.

genirq: Export enable/disable_percpu_irq()

2013-02-18T20:42:25+00:00

These functions are used by the tilegx onchip network driver, and it's
useful to be able to load that driver as a module.

Signed-off-by: Chris Metcalf 
Link: http://lkml.kernel.org/r/201302012043.r11KhNZF024371@farm-0021.internal.tilera.com
Signed-off-by: Thomas Gleixner

sched/rt: Move rt specific bits into new header file

2013-02-07T19:51:08+00:00

Move rt scheduler definitions out of include/linux/sched.h into
new file include/linux/sched/rt.h

Signed-off-by: Clark Williams 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Link: http://lkml.kernel.org/r/20130207094707.7b9f825f@riff.lan
Signed-off-by: Ingo Molnar

irq: tsk->comm is an array

2012-12-18T23:02:11+00:00

The array check is useless so remove it.

[akpm@linux-foundation.org: remove comment, per David]
Signed-off-by: Alan Cox 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds