kernel_optimize_test/include/linux/freezer.h
Rafael J. Wysocki ba96a0c880 freezer: fix vfork problem
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 <rjw@sisk.pl>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-23 20:14:11 -07:00

145 lines
3.7 KiB
C++

/* Freezer declarations */
#include <linux/sched.h>
#ifdef CONFIG_PM
/*
* Check if a process has been frozen
*/
static inline int frozen(struct task_struct *p)
{
return p->flags & PF_FROZEN;
}
/*
* Check if there is a request to freeze a process
*/
static inline int freezing(struct task_struct *p)
{
return test_tsk_thread_flag(p, TIF_FREEZE);
}
/*
* Request that a process be frozen
*/
static inline void freeze(struct task_struct *p)
{
set_tsk_thread_flag(p, TIF_FREEZE);
}
/*
* Sometimes we may need to cancel the previous 'freeze' request
*/
static inline void do_not_freeze(struct task_struct *p)
{
clear_tsk_thread_flag(p, TIF_FREEZE);
}
/*
* Wake up a frozen process
*
* task_lock() is taken to prevent the race with refrigerator() which may
* occur if the freezing of tasks fails. Namely, without the lock, if the
* freezing of tasks failed, thaw_tasks() might have run before a task in
* refrigerator() could call frozen_process(), in which case the task would be
* frozen and no one would thaw it.
*/
static inline int thaw_process(struct task_struct *p)
{
task_lock(p);
if (frozen(p)) {
p->flags &= ~PF_FROZEN;
task_unlock(p);
wake_up_process(p);
return 1;
}
clear_tsk_thread_flag(p, TIF_FREEZE);
task_unlock(p);
return 0;
}
/*
* freezing is complete, mark process as frozen
*/
static inline void frozen_process(struct task_struct *p)
{
p->flags |= PF_FROZEN;
wmb();
clear_tsk_thread_flag(p, TIF_FREEZE);
}
extern void refrigerator(void);
extern int freeze_processes(void);
extern void thaw_processes(void);
static inline int try_to_freeze(void)
{
if (freezing(current)) {
refrigerator();
return 1;
} else
return 0;
}
/*
* The PF_FREEZER_SKIP flag should be set by a vfork parent right before it
* calls wait_for_completion(&vfork) and reset right after it returns from this
* function. Next, the parent should call try_to_freeze() to freeze itself
* appropriately in case the child has exited before the freezing of tasks is
* complete. However, we don't want kernel threads to be frozen in unexpected
* places, so we allow them to block freeze_processes() instead or to set
* PF_NOFREEZE if needed and PF_FREEZER_SKIP is only set for userland vfork
* parents. Fortunately, in the ____call_usermodehelper() case the parent won't
* really block freeze_processes(), since ____call_usermodehelper() (the child)
* does a little before exec/exit and it can't be frozen before waking up the
* parent.
*/
/*
* If the current task is a user space one, tell the freezer not to count it as
* freezable.
*/
static inline void freezer_do_not_count(void)
{
if (current->mm)
current->flags |= PF_FREEZER_SKIP;
}
/*
* If the current task is a user space one, tell the freezer to count it as
* freezable again and try to freeze it.
*/
static inline void freezer_count(void)
{
if (current->mm) {
current->flags &= ~PF_FREEZER_SKIP;
try_to_freeze();
}
}
/*
* Check if the task should be counted as freezeable by the freezer
*/
static inline int freezer_should_skip(struct task_struct *p)
{
return !!(p->flags & PF_FREEZER_SKIP);
}
#else
static inline int frozen(struct task_struct *p) { return 0; }
static inline int freezing(struct task_struct *p) { return 0; }
static inline void freeze(struct task_struct *p) { BUG(); }
static inline int thaw_process(struct task_struct *p) { return 1; }
static inline void frozen_process(struct task_struct *p) { BUG(); }
static inline void refrigerator(void) {}
static inline int freeze_processes(void) { BUG(); return 0; }
static inline void thaw_processes(void) {}
static inline int try_to_freeze(void) { return 0; }
static inline void freezer_do_not_count(void) {}
static inline void freezer_count(void) {}
static inline int freezer_should_skip(struct task_struct *p) { return 0; }
#endif