linux-toradex.git/kernel/exit.c, branch v2.6.17.12

[PATCH] Link error when futexes are disabled on 64bit architectures

2006-06-30T00:17:17+00:00

From: Anton Blanchard 

If futexes are disabled we fail to link on ppc64.

Signed-off-by: Anton Blanchard 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Chris Wright

[PATCH] run_posix_cpu_timers: remove a bogus BUG_ON()

2006-06-17T17:52:13+00:00

do_exit() clears ->it_##clock##_expires, but nothing prevents
another cpu to attach the timer to exiting process after that.
arm_timer() tries to protect against this race, but the check
is racy.

After exit_notify() does 'write_unlock_irq(&tasklist_lock)' and
before do_exit() calls 'schedule() local timer interrupt can find
tsk->exit_state != 0. If that state was EXIT_DEAD (or another cpu
does sys_wait4) interrupted task has ->signal == NULL.

At this moment exiting task has no pending cpu timers, they were
cleanuped in __exit_signal()->posix_cpu_timers_exit{,_group}(),
so we can just return from irq.

John Stultz recently confirmed this bug, see

	http://marc.theaimsgroup.com/?l=linux-kernel&m=115015841413687

Signed-off-by: Oleg Nesterov 
Signed-off-by: Linus Torvalds

[PATCH] move call of audit_free() into do_exit()

2006-05-01T10:06:13+00:00

Signed-off-by: Al Viro

[PATCH] task: Make task list manipulations RCU safe

2006-04-19T16:13:49+00:00

While we can currently walk through thread groups, process groups, and
sessions with just the rcu_read_lock, this opens the door to walking the
entire task list.

We already have all of the other RCU guarantees so there is no cost in
doing this, this should be enough so that proc can stop taking the
tasklist lock during readdir.

prev_task was killed because it has no users, and using it will miss new
tasks when doing an rcu traversal.

Signed-off-by: Eric W. Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] splice: add direct fd <-> fd splicing support

2006-04-11T11:52:07+00:00

It's more efficient for sendfile() emulation. Basically we cache an
internal private pipe and just use that as the intermediate area for
pages. Direct splicing is not available from sys_splice(), it is only
meant to be used for sendfile() emulation.

Additional patch from Ingo Molnar to avoid the PIPE_BUFFERS loop at
exit for the normal fast path.

Signed-off-by: Jens Axboe

[PATCH] task: RCU protect task->usage

2006-03-31T20:18:59+00:00

A big problem with rcu protected data structures that are also reference
counted is that you must jump through several hoops to increase the reference
count.  I think someone finally implemented atomic_inc_not_zero(&count) to
automate the common case.  Unfortunately this means you must special case the
rcu access case.

When data structures are only visible via rcu in a manner that is not
determined by the reference count on the object (i.e.  tasks are visible until
their zombies are reaped) there is a much simpler technique we can employ.
Simply delaying the decrement of the reference count until the rcu interval is
over.

What that means is that the proc code that looks up a task and later
wants to sleep can now do:

rcu_read_lock();
task = find_task_by_pid(some_pid);
if (task) {
	get_task_struct(task);
}
rcu_read_unlock();

The effect on the rest of the kernel is that put_task_struct becomes cheaper
and immediate, and in the case where the task has been reaped it frees the
task immediate instead of unnecessarily waiting an until the rcu interval is
over.

Cleanup of task_struct does not happen when its reference count drops to
zero, instead cleanup happens when release_task is called.  Tasks can only
be looked up via rcu before release_task is called.  All rcu protected
members of task_struct are freed by release_task.

Therefore we can move call_rcu from put_task_struct into release_task.  And
we can modify release_task to not immediately release the reference count
but instead have it call put_task_struct from the function it gives to
call_rcu.

The end result:

- get_task_struct is safe in an rcu context where we have just looked
  up the task.

- put_task_struct() simplifies into its old pre rcu self.

This reorganization also makes put_task_struct uncallable from modules as
it is not exported but it does not appear to be called from any modules so
this should not be an issue, and is trivially fixed.

Signed-off-by: Eric W. Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] cleanup __exit_signal->cleanup_sighand path

2006-03-29T02:36:44+00:00

Move 'tsk->sighand = NULL' from cleanup_sighand() to __exit_signal().  This
makes the exit path more understandable and allows us to do
cleanup_sighand() outside of ->siglock protected section.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] pids: kill PIDTYPE_TGID

2006-03-29T02:36:44+00:00

This patch kills PIDTYPE_TGID pid_type thus saving one hash table in
kernel/pid.c and speeding up subthreads create/destroy a bit.  It is also a
preparation for the further tref/pids rework.

This patch adds 'struct list_head thread_group' to 'struct task_struct'
instead.

We don't detach group leader from PIDTYPE_PID namespace until another
thread inherits it's ->pid == ->tgid, so we are safe wrt premature
free_pidmap(->tgid) call.

Currently there are no users of find_task_by_pid_type(PIDTYPE_TGID).
Should the need arise, we can use find_task_by_pid()->group_leader.

Signed-off-by: Oleg Nesterov 
Acked-By: Eric Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] do_group_exit: don't take tasklist_lock

2006-03-29T02:36:43+00:00

do_group_exit() takes tasklist_lock for zap_other_threads(), this is unneeded
now.

Signed-off-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

[PATCH] do __unhash_process() under ->siglock

2006-03-29T02:36:43+00:00

This patch moves __unhash_process() call from realease_task() to
__exit_signal(), so __detach_pid() is called with ->siglock held.

This means we don't need tasklist_lock to iterate over thread group anymore:

	copy_process() was already changed to do attach_pid()
	under ->siglock.

	Eric's "pidhash-kill-switch_exec_pids.patch" from -mm
	changed de_thread() so it doesn't touch PIDTYPE_TGID.

NOTE: de_thread() still needs some attention.  It still changes task->pid
lockless.  Taking ->sighand.siglock here allows to do more tasklist_lock
removals.

Signed-off-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds