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authorChristoph Lameter <christoph@lameter.com>2005-06-25 02:13:50 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-25 20:10:13 -0400
commit3e1d1d28d99dabe63c64f7f40f1ca1d646de1f73 (patch)
treed1e7c1e2e8902072042aefc3a7976b271cf76021 /kernel/power
parentb3e112bcc19abd8e9657dca34a87316786e096f3 (diff)
[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')
-rw-r--r--kernel/power/process.c26
1 files changed, 10 insertions, 16 deletions
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 78d92dc6a1ed..0a086640bcfc 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -32,7 +32,7 @@ static inline int freezeable(struct task_struct * p)
32} 32}
33 33
34/* Refrigerator is place where frozen processes are stored :-). */ 34/* Refrigerator is place where frozen processes are stored :-). */
35void refrigerator(unsigned long flag) 35void refrigerator(void)
36{ 36{
37 /* Hmm, should we be allowed to suspend when there are realtime 37 /* Hmm, should we be allowed to suspend when there are realtime
38 processes around? */ 38 processes around? */
@@ -41,14 +41,13 @@ void refrigerator(unsigned long flag)
41 current->state = TASK_UNINTERRUPTIBLE; 41 current->state = TASK_UNINTERRUPTIBLE;
42 pr_debug("%s entered refrigerator\n", current->comm); 42 pr_debug("%s entered refrigerator\n", current->comm);
43 printk("="); 43 printk("=");
44 current->flags &= ~PF_FREEZE;
45 44
45 frozen_process(current);
46 spin_lock_irq(&current->sighand->siglock); 46 spin_lock_irq(&current->sighand->siglock);
47 recalc_sigpending(); /* We sent fake signal, clean it up */ 47 recalc_sigpending(); /* We sent fake signal, clean it up */
48 spin_unlock_irq(&current->sighand->siglock); 48 spin_unlock_irq(&current->sighand->siglock);
49 49
50 current->flags |= PF_FROZEN; 50 while (frozen(current))
51 while (current->flags & PF_FROZEN)
52 schedule(); 51 schedule();
53 pr_debug("%s left refrigerator\n", current->comm); 52 pr_debug("%s left refrigerator\n", current->comm);
54 current->state = save; 53 current->state = save;
@@ -57,10 +56,10 @@ void refrigerator(unsigned long flag)
57/* 0 = success, else # of processes that we failed to stop */ 56/* 0 = success, else # of processes that we failed to stop */
58int freeze_processes(void) 57int freeze_processes(void)
59{ 58{
60 int todo; 59 int todo;
61 unsigned long start_time; 60 unsigned long start_time;
62 struct task_struct *g, *p; 61 struct task_struct *g, *p;
63 62
64 printk( "Stopping tasks: " ); 63 printk( "Stopping tasks: " );
65 start_time = jiffies; 64 start_time = jiffies;
66 do { 65 do {
@@ -70,14 +69,12 @@ int freeze_processes(void)
70 unsigned long flags; 69 unsigned long flags;
71 if (!freezeable(p)) 70 if (!freezeable(p))
72 continue; 71 continue;
73 if ((p->flags & PF_FROZEN) || 72 if ((frozen(p)) ||
74 (p->state == TASK_TRACED) || 73 (p->state == TASK_TRACED) ||
75 (p->state == TASK_STOPPED)) 74 (p->state == TASK_STOPPED))
76 continue; 75 continue;
77 76
78 /* FIXME: smp problem here: we may not access other process' flags 77 freeze(p);
79 without locking */
80 p->flags |= PF_FREEZE;
81 spin_lock_irqsave(&p->sighand->siglock, flags); 78 spin_lock_irqsave(&p->sighand->siglock, flags);
82 signal_wake_up(p, 0); 79 signal_wake_up(p, 0);
83 spin_unlock_irqrestore(&p->sighand->siglock, flags); 80 spin_unlock_irqrestore(&p->sighand->siglock, flags);
@@ -91,7 +88,7 @@ int freeze_processes(void)
91 return todo; 88 return todo;
92 } 89 }
93 } while(todo); 90 } while(todo);
94 91
95 printk( "|\n" ); 92 printk( "|\n" );
96 BUG_ON(in_atomic()); 93 BUG_ON(in_atomic());
97 return 0; 94 return 0;
@@ -106,10 +103,7 @@ void thaw_processes(void)
106 do_each_thread(g, p) { 103 do_each_thread(g, p) {
107 if (!freezeable(p)) 104 if (!freezeable(p))
108 continue; 105 continue;
109 if (p->flags & PF_FROZEN) { 106 if (!thaw_process(p))
110 p->flags &= ~PF_FROZEN;
111 wake_up_process(p);
112 } else
113 printk(KERN_INFO " Strange, %s not stopped\n", p->comm ); 107 printk(KERN_INFO " Strange, %s not stopped\n", p->comm );
114 } while_each_thread(g, p); 108 } while_each_thread(g, p);
115 109