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[PATCH] Cleanup patch for process freezing

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1. Establish a simple API for process freezing defined in linux/include/sched.h:

   frozen(process)		Check for frozen process
   freezing(process)		Check if a process is being frozen
   freeze(process)		Tell a process to freeze (go to refrigerator)
   thaw_process(process)	Restart process
   frozen_process(process)	Process is frozen now

2. Remove all references to PF_FREEZE and PF_FROZEN from all
   kernel sources except sched.h

3. Fix numerous locations where try_to_freeze is manually done by a driver

4. Remove the argument that is no longer necessary from two function calls.

5. Some whitespace cleanup

6. Clear potential race in refrigerator (provides an open window of PF_FREEZE
   cleared before setting PF_FROZEN, recalc_sigpending does not check
   PF_FROZEN).

This patch does not address the problem of freeze_processes() violating the rule
that a task may only modify its own flags by setting PF_FREEZE. This is not clean
in an SMP environment. freeze(process) is therefore not SMP safe!

Signed-off-by: Christoph Lameter <christoph@lameter.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Christoph Lameter
2005-06-24 23:13:50 -07:00
committed by Linus Torvalds
parent b3e112bcc1
commit 3e1d1d28d9
47 changed files with 126 additions and 113 deletions
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73
include/linux/sched.h
View File

@@ -1245,33 +1245,78 @@ extern void normalize_rt_tasks(void);
#endif
/* try_to_freeze
*
* Checks whether we need to enter the refrigerator
* and returns 1 if we did so.
*/
#ifdef CONFIG_PM
extern void refrigerator(unsigned long);
/*
* 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 p->flags & PF_FREEZE;
}
/*
* Request that a process be frozen
* FIXME: SMP problem. We may not modify other process' flags!
*/
static inline void freeze(struct task_struct *p)
{
p->flags |= PF_FREEZE;
}
/*
* Wake up a frozen process
*/
static inline int thaw_process(struct task_struct *p)
{
if (frozen(p)) {
p->flags &= ~PF_FROZEN;
wake_up_process(p);
return 1;
}
return 0;
}
/*
* freezing is complete, mark process as frozen
*/
static inline void frozen_process(struct task_struct *p)
{
p->flags = (p->flags & ~PF_FREEZE) | PF_FROZEN;
}
extern void refrigerator(void);
extern int freeze_processes(void);
extern void thaw_processes(void);
static inline int try_to_freeze(unsigned long refrigerator_flags)
static inline int try_to_freeze(void)
{
if (unlikely(current->flags & PF_FREEZE)) {
refrigerator(refrigerator_flags);
if (freezing(current)) {
refrigerator();
return 1;
} else
return 0;
}
#else
static inline void refrigerator(unsigned long flag) {}
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(unsigned long refrigerator_flags)
{
return 0;
}
static inline int try_to_freeze(void) { return 0; }
#endif /* CONFIG_PM */
#endif /* __KERNEL__ */