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

kernel/kthread.c:kthread_create_on_node(): clarify documentation

2015-09-04T23:54:41+00:00

- Make it clear that the `node' arg refers to memory allocations only:
  kthread_create_on_node() does not pin the new thread to that node's
  CPUs.

- Encourage the use of NUMA_NO_NODE.

[nzimmer@sgi.com: use NUMA_NO_NODE in kthread_create() also]
Cc: Nathan Zimmer 
Cc: Tejun Heo 
Cc: Eric Dumazet 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sched: Fix a race between __kthread_bind() and sched_setaffinity()

2015-08-12T10:06:09+00:00

Because sched_setscheduler() checks p->flags & PF_NO_SETAFFINITY
without locks, a caller might observe an old value and race with the
set_cpus_allowed_ptr() call from __kthread_bind() and effectively undo
it:

	__kthread_bind()
	  do_set_cpus_allowed()
						
						  sched_setaffinity()
						    if (p->flags & PF_NO_SETAFFINITIY)
						    set_cpus_allowed_ptr()
	  p->flags |= PF_NO_SETAFFINITY

Fix the bug by putting everything under the regular scheduler locks.

This also closes a hole in the serialization of task_struct::{nr_,}cpus_allowed.

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Tejun Heo 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Oleg Nesterov 
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/20150515154833.545640346@infradead.org
Signed-off-by: Ingo Molnar

kthread_work: remove the unused wait_queue_head

2014-07-28T18:16:30+00:00

The wait_queue_head_t kthread_work->done is unused since
flush_kthread_work() has been re-implemented.  Let's remove it
including the initialization code.  This makes
DEFINE_KTHREAD_WORK_ONSTACK() unnecessary, removed.

tj: Updated description.  Removed DEFINE_KTHREAD_WORK_ONSTACK().

Signed-off-by: Lai Jiangshan 
Signed-off-by: Tejun Heo

kthread: implement probe_kthread_data()

2013-05-01T00:04:02+00:00

One of the problems that arise when converting dedicated custom threadpool
to workqueue is that the shared worker pool used by workqueue anonimizes
each worker making it more difficult to identify what the worker was doing
on which target from the output of sysrq-t or debug dump from oops, BUG()
and friends.

For example, after writeback is converted to use workqueue instead of
priviate thread pool, there's no easy to tell which backing device a
writeback work item was working on at the time of task dump, which,
according to our writeback brethren, is important in tracking down issues
with a lot of mounted file systems on a lot of different devices.

This patchset implements a way for a work function to mark its execution
instance so that task dump of the worker task includes information to
indicate what the work item was doing.

An example WARN dump would look like the following.

 WARNING: at fs/fs-writeback.c:1015 bdi_writeback_workfn+0x2b4/0x3c0()
 Modules linked in:
 CPU: 0 Pid: 28 Comm: kworker/u18:0 Not tainted 3.9.0-rc1-work+ #24
 Hardware name: empty empty/S3992, BIOS 080011  10/26/2007
 Workqueue: writeback bdi_writeback_workfn (flush-8:16)
  ffffffff820a3a98 ffff88015b927cb8 ffffffff81c61855 ffff88015b927cf8
  ffffffff8108f500 0000000000000000 ffff88007a171948 ffff88007a1716b0
  ffff88015b49df00 ffff88015b8d3940 0000000000000000 ffff88015b927d08
 Call Trace:
  [] dump_stack+0x19/0x1b
  [] warn_slowpath_common+0x70/0xa0
  ...

This patch:

Implement probe_kthread_data() which returns kthread_data if accessible.
The function is equivalent to kthread_data() except that the specified
@task may not be a kthread or its vfork_done is already cleared rendering
struct kthread inaccessible.  In the former case, probe_kthread_data() may
return any value.  In the latter, NULL.

This will be used to safely print debug information without affecting
synchronization in the normal paths.  Workqueue debug info printing on
dump_stack() and friends will make use of it.

Signed-off-by: Tejun Heo 
Cc: Oleg Nesterov 
Acked-by: Jan Kara 
Cc: Dave Chinner 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kthread: Implement park/unpark facility

2012-08-13T15:01:06+00:00

To avoid the full teardown/setup of per cpu kthreads in the case of
cpu hot(un)plug, provide a facility which allows to put the kthread
into a park position and unpark it when the cpu comes online again.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Namhyung Kim 
Cc: Peter Zijlstra 
Reviewed-by: Srivatsa S. Bhat 
Cc: Rusty Russell 
Reviewed-by: Paul E. McKenney 
Link: http://lkml.kernel.org/r/20120716103948.236618824@linutronix.de
Signed-off-by: Thomas Gleixner

kthread_worker: reimplement flush_kthread_work() to allow freeing the work item being executed

2012-07-22T17:15:28+00:00

kthread_worker provides minimalistic workqueue-like interface for
users which need a dedicated worker thread (e.g. for realtime
priority).  It has basic queue, flush_work, flush_worker operations
which mostly match the workqueue counterparts; however, due to the way
flush_work() is implemented, it has a noticeable difference of not
allowing work items to be freed while being executed.

While the current users of kthread_worker are okay with the current
behavior, the restriction does impede some valid use cases.  Also,
removing this difference isn't difficult and actually makes the code
easier to understand.

This patch reimplements flush_kthread_work() such that it uses a
flush_work item instead of queue/done sequence numbers.

Signed-off-by: Tejun Heo

freezer: implement and use kthread_freezable_should_stop()

2011-11-21T20:32:23+00:00

Writeback and thinkpad_acpi have been using thaw_process() to prevent
deadlock between the freezer and kthread_stop(); unfortunately, this
is inherently racy - nothing prevents freezing from happening between
thaw_process() and kthread_stop().

This patch implements kthread_freezable_should_stop() which enters
refrigerator if necessary but is guaranteed to return if
kthread_stop() is invoked.  Both thaw_process() users are converted to
use the new function.

Note that this deadlock condition exists for many of freezable
kthreads.  They need to be converted to use the new should_stop or
freezable workqueue.

Tested with synthetic test case.

Signed-off-by: Tejun Heo 
Acked-by: Henrique de Moraes Holschuh 
Cc: Jens Axboe 
Cc: Oleg Nesterov

treewide: use printf not attribute__((format(printf,...)))

2011-11-01T00:30:54+00:00

Standardize the style for compiler based printf format verification.
Standardized the location of __printf too.

Done via script and a little typing.

$ grep -rPl --include=*.[ch] -w "__attribute__" * | \
  grep -vP "^(tools|scripts|include/linux/compiler-gcc.h)" | \
  xargs perl -n -i -e 'local $/; while (<>) { s/\b__attribute__\s*\(\s*\(\s*format\s*\(\s*printf\s*,\s*(.+)\s*,\s*(.+)\s*\)\s*\)\s*\)/__printf($1, $2)/g ; print; }'

[akpm@linux-foundation.org: revert arch bits]
Signed-off-by: Joe Perches 
Cc: "Kirill A. Shutemov" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kthread: NUMA aware kthread_create_on_node()

2011-03-23T00:44:01+00:00

All kthreads being created from a single helper task, they all use memory
from a single node for their kernel stack and task struct.

This patch suite creates kthread_create_on_node(), adding a 'cpu' parameter
to parameters already used by kthread_create().

This parameter serves in allocating memory for the new kthread on its
memory node if possible.

Signed-off-by: Eric Dumazet 
Acked-by: David S. Miller 
Reviewed-by: Andi Kleen 
Acked-by: Rusty Russell 
Cc: Tejun Heo 
Cc: Tony Luck 
Cc: Fenghua Yu 
Cc: David Howells 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kthread: Replace deprecated spinlock initialization

2011-01-27T11:30:37+00:00

SPIN_LOCK_UNLOCK is deprecated. Use the lockdep capable variant
instead.

Signed-off-by: Thomas Gleixner