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authorChristoph Lameter <christoph@lameter.com>2005-06-24 23:13:50 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-25 17:10:13 -0700
commit3e1d1d28d99dabe63c64f7f40f1ca1d646de1f73 (patch)
treed1e7c1e2e8902072042aefc3a7976b271cf76021 /kernel
parentb3e112bcc19abd8e9657dca34a87316786e096f3 (diff)
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[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')
-rw-r--r--kernel/power/process.c26
-rw-r--r--kernel/sched.c3
-rw-r--r--kernel/signal.c5
3 files changed, 13 insertions, 21 deletions
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 78d92dc6a1e..0a086640bcf 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(&current->sighand->siglock);
recalc_sigpending(); /* We sent fake signal, clean it up */
spin_unlock_irq(&current->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);
diff --git a/kernel/sched.c b/kernel/sched.c
index 76080d142e3..6fa9ea4ae44 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4174,8 +4174,7 @@ static int migration_thread(void * data)
struct list_head *head;
migration_req_t *req;
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();
spin_lock_irq(&rq->lock);
diff --git a/kernel/signal.c b/kernel/signal.c
index d1258729a5f..ca1186eef93 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -213,7 +213,7 @@ static inline int has_pending_signals(sigset_t *signal, sigset_t *blocked)
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 @@ sys_rt_sigtimedwait(const sigset_t __user *uthese,
current->state = TASK_INTERRUPTIBLE;
timeout = schedule_timeout(timeout);
- if (current->flags & PF_FREEZE)
- refrigerator(PF_FREEZE);
+ try_to_freeze();
spin_lock_irq(&current->sighand->siglock);
sig = dequeue_signal(current, &these, &info);
current->blocked = current->real_blocked;