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author | Christoph Lameter <christoph@lameter.com> | 2005-06-25 06:13:50 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-06-26 00:10:13 (GMT) |
commit | 3e1d1d28d99dabe63c64f7f40f1ca1d646de1f73 (patch) | |
tree | d1e7c1e2e8902072042aefc3a7976b271cf76021 /kernel/power/process.c | |
parent | b3e112bcc19abd8e9657dca34a87316786e096f3 (diff) | |
download | linux-3e1d1d28d99dabe63c64f7f40f1ca1d646de1f73.tar.xz |
[PATCH] Cleanup patch for process freezing
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>
Diffstat (limited to 'kernel/power/process.c')
-rw-r--r-- | kernel/power/process.c | 26 |
1 files changed, 10 insertions, 16 deletions
diff --git a/kernel/power/process.c b/kernel/power/process.c index 78d92dc..0a08664 100644 --- a/kernel/power/process.c +++ b/kernel/power/process.c @@ -32,7 +32,7 @@ static inline int freezeable(struct task_struct * p) } /* Refrigerator is place where frozen processes are stored :-). */ -void refrigerator(unsigned long flag) +void refrigerator(void) { /* Hmm, should we be allowed to suspend when there are realtime processes around? */ @@ -41,14 +41,13 @@ void refrigerator(unsigned long flag) current->state = TASK_UNINTERRUPTIBLE; pr_debug("%s entered refrigerator\n", current->comm); printk("="); - current->flags &= ~PF_FREEZE; + frozen_process(current); spin_lock_irq(¤t->sighand->siglock); recalc_sigpending(); /* We sent fake signal, clean it up */ spin_unlock_irq(¤t->sighand->siglock); - current->flags |= PF_FROZEN; - while (current->flags & PF_FROZEN) + while (frozen(current)) schedule(); pr_debug("%s left refrigerator\n", current->comm); current->state = save; @@ -57,10 +56,10 @@ void refrigerator(unsigned long flag) /* 0 = success, else # of processes that we failed to stop */ int freeze_processes(void) { - int todo; - unsigned long start_time; + int todo; + unsigned long start_time; struct task_struct *g, *p; - + printk( "Stopping tasks: " ); start_time = jiffies; do { @@ -70,14 +69,12 @@ int freeze_processes(void) unsigned long flags; if (!freezeable(p)) continue; - if ((p->flags & PF_FROZEN) || + if ((frozen(p)) || (p->state == TASK_TRACED) || (p->state == TASK_STOPPED)) continue; - /* FIXME: smp problem here: we may not access other process' flags - without locking */ - p->flags |= PF_FREEZE; + freeze(p); spin_lock_irqsave(&p->sighand->siglock, flags); signal_wake_up(p, 0); spin_unlock_irqrestore(&p->sighand->siglock, flags); @@ -91,7 +88,7 @@ int freeze_processes(void) return todo; } } while(todo); - + printk( "|\n" ); BUG_ON(in_atomic()); return 0; @@ -106,10 +103,7 @@ void thaw_processes(void) do_each_thread(g, p) { if (!freezeable(p)) continue; - if (p->flags & PF_FROZEN) { - p->flags &= ~PF_FROZEN; - wake_up_process(p); - } else + if (!thaw_process(p)) printk(KERN_INFO " Strange, %s not stopped\n", p->comm ); } while_each_thread(g, p); |