[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>
diff --git a/kernel/signal.c b/kernel/signal.c
index d125872..ca1186ee 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -213,7 +213,7 @@
fastcall void recalc_sigpending_tsk(struct task_struct *t)
{
if (t->signal->group_stop_count > 0 ||
- (t->flags & PF_FREEZE) ||
+ (freezing(t)) ||
PENDING(&t->pending, &t->blocked) ||
PENDING(&t->signal->shared_pending, &t->blocked))
set_tsk_thread_flag(t, TIF_SIGPENDING);
@@ -2231,8 +2231,7 @@
current->state = TASK_INTERRUPTIBLE;
timeout = schedule_timeout(timeout);
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();
spin_lock_irq(¤t->sighand->siglock);
sig = dequeue_signal(current, &these, &info);
current->blocked = current->real_blocked;