linux-toradex.git/kernel/power/process.c, branch v2.6.23.12

Freezer: remove redundant check in try_to_freeze_tasks

2007-07-19T17:04:42+00:00

We don't need to check if todo is positive before calling time_after() in
try_to_freeze_tasks(), because if todo is zero at this point, the loop will be
broken anyway due to the while () condition being false.

Signed-off-by: Rafael J. Wysocki 
Acked-by: Pavel Machek 
Cc: Gautham R Shenoy 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Freezer: return int from freeze_processes

2007-07-19T17:04:42+00:00

Make try_to_freeze_tasks() and freeze_processes() return -EBUSY on failure
instead of the number of unfrozen tasks (none of the callers actually uses
this number).

Signed-off-by: Rafael J. Wysocki 
Acked-by: Pavel Machek 
Cc: Gautham R Shenoy 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Freezer: use __set_current_state in refrigerator

2007-07-19T17:04:42+00:00

Use __set_current_state() as appropriate in refrigerator() instead of
accessing current->state directly.

Signed-off-by: Rafael J. Wysocki 
Acked-by: Pavel Machek 
Cc: Gautham R Shenoy 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Freezer: avoid freezing kernel threads prematurely

2007-07-19T17:04:42+00:00

Kernel threads should not have TIF_FREEZE set when user space processes are
being frozen, since otherwise some of them might be frozen prematurely.
To prevent this from happening we can (1) make exit_mm() unset TIF_FREEZE
unconditionally just after clearing tsk->mm and (2) make try_to_freeze_tasks()
check if p->mm is different from zero and PF_BORROWED_MM is unset in p->flags
when user space processes are to be frozen.

Namely, when user space processes are being frozen, we only should set
TIF_FREEZE for tasks that have p->mm different from NULL and don't have
PF_BORROWED_MM set in p->flags.  For this reason task_lock() must be used to
prevent try_to_freeze_tasks() from racing with use_mm()/unuse_mm(), in which
p->mm and p->flags.PF_BORROWED_MM are changed under task_lock(p).  Also, we
need to prevent the following scenario from happening:

* daemonize() is called by a task spawned from a user space code path
* freezer checks if the task has p->mm set and the result is positive
* task enters exit_mm() and clears its TIF_FREEZE
* freezer sets TIF_FREEZE for the task
* task calls try_to_freeze() and goes to the refrigerator, which is wrong at
  that point

This requires us to acquire task_lock(p) before p->flags.PF_BORROWED_MM and
p->mm are examined and release it after TIF_FREEZE is set for p (or it turns
out that TIF_FREEZE should not be set).

Signed-off-by: Rafael J. Wysocki 
Cc: Gautham R Shenoy 
Cc: Pavel Machek 
Cc: Nigel Cunningham 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

freezer: run show_state() when freezing times out

2007-07-19T17:04:42+00:00

To see which tasks are stuck where.

Cc: "Rafael J. Wysocki" 
Cc: Oleg Nesterov 
Cc: Alan Stern 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

recalc_sigpending_tsk fixes

2007-05-24T03:14:12+00:00

Steve Hawkes discovered a problem where recalc_sigpending_tsk was called in
do_sigaction but no signal_wake_up call was made, preventing later signals
from waking up blocked threads with TIF_SIGPENDING already set.

In fact, the few other calls to recalc_sigpending_tsk outside the signals
code are also subject to this problem in other race conditions.

This change makes recalc_sigpending_tsk private to the signals code.  It
changes the outside calls, as well as do_sigaction, to use the new
recalc_sigpending_and_wake instead.

Signed-off-by: Roland McGrath 
Cc: 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

freezer: move frozen_process() to kernel/power/process.c

2007-05-24T03:14:11+00:00

Other than refrigerator, no one else calls frozen_process().  So move it from
include/linux/freezer.h to kernel/power/process.c.

Also, since a task can be marked as frozen by itself, we don't need to pass
the (struct task_struct *p) parameter to frozen_process().

Signed-off-by: Gautham R Shenoy 
Signed-off-by: Rafael J. Wysocki 
Cc: Oleg Nesterov 
Cc: Pavel Machek 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

freezer: take kernel_execve into consideration

2007-05-24T03:14:11+00:00

Kernel threads can become userland processes by calling kernel_execve().

In particular, this may happen right after the try_to_freeze_tasks()
called with FREEZER_USER_SPACE has returned, so try_to_freeze_tasks()
needs to take userspace processes into consideration even if it is
called with FREEZER_KERNEL_THREADS.

Signed-off-by: Rafael J. Wysocki 
Acked-by: Pavel Machek 
Cc: Gautham R Shenoy 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

freezer: fix vfork problem

2007-05-24T03:14:11+00:00

Currently try_to_freeze_tasks() has to wait until all of the vforked processes
exit and for this reason every user can make it fail.  To fix this problem we
can introduce the additional process flag PF_FREEZER_SKIP to be used by tasks
that do not want to be counted as freezable by the freezer and want to have
TIF_FREEZE set nevertheless.  Then, this flag can be set by tasks using
sys_vfork() before they call wait_for_completion(&vfork) and cleared after
they have woken up.  After clearing it, the tasks should call try_to_freeze()
as soon as possible.

Signed-off-by: Rafael J. Wysocki 
Cc: Gautham R Shenoy 
Cc: Oleg Nesterov 
Cc: Pavel Machek 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

freezer: close potential race between refrigerator and thaw_tasks

2007-05-24T03:14:10+00:00

If the freezing of tasks fails and a task is preempted in refrigerator()
before calling frozen_process(), then thaw_tasks() may run before this task is
frozen.  In that case the task will freeze and no one will thaw it.

To fix this race we can call freezing(current) in refrigerator() along with
frozen_process(current) under the task_lock() which also should be taken in
the error path of try_to_freeze_tasks() as well as in thaw_process().
Moreover, if thaw_process() additionally clears TIF_FREEZE for tasks that are
not frozen, we can be sure that all tasks are thawed and there are no pending
"freeze" requests after thaw_tasks() has run.

Signed-off-by: Rafael J. Wysocki 
Acked-by: Pavel Machek 
Cc: Gautham R Shenoy 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds