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authorRoland McGrath <roland@redhat.com>2008-03-03 20:22:05 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 07:59:54 -0800
commit13b1c3d4b49bd83d861c775ca2db54e1692a1b07 (patch)
tree6cefdfef300d3431f2b2b32ec86000b0132bd762
parent976dde010e513a9c7c3117a32b7b015f84b37430 (diff)
freezer vs stopped or traced
This changes the "freezer" code used by suspend/hibernate in its treatment of tasks in TASK_STOPPED (job control stop) and TASK_TRACED (ptrace) states. As I understand it, the intent of the "freezer" is to hold all tasks from doing anything significant. For this purpose, TASK_STOPPED and TASK_TRACED are "frozen enough". It's possible the tasks might resume from ptrace calls (if the tracer were unfrozen) or from signals (including ones that could come via timer interrupts, etc). But this doesn't matter as long as they quickly block again while "freezing" is in effect. Some minor adjustments to the signal.c code make sure that try_to_freeze() very shortly follows all wakeups from both kinds of stop. This lets the freezer code safely leave stopped tasks unmolested. Changing this fixes the longstanding bug of seeing after resuming from suspend/hibernate your shell report "[1] Stopped" and the like for all your jobs stopped by ^Z et al, as if you had freshly fg'd and ^Z'd them. It also removes from the freezer the arcane special case treatment for ptrace'd tasks, which relied on intimate knowledge of ptrace internals. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/power/process.c29
-rw-r--r--kernel/signal.c16
2 files changed, 26 insertions, 19 deletions
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 7c2118f9597..f1d0b345c9b 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -75,22 +75,15 @@ void refrigerator(void)
__set_current_state(save);
}
-static void fake_signal_wake_up(struct task_struct *p, int resume)
+static void fake_signal_wake_up(struct task_struct *p)
{
unsigned long flags;
spin_lock_irqsave(&p->sighand->siglock, flags);
- signal_wake_up(p, resume);
+ signal_wake_up(p, 0);
spin_unlock_irqrestore(&p->sighand->siglock, flags);
}
-static void send_fake_signal(struct task_struct *p)
-{
- if (task_is_stopped(p))
- force_sig_specific(SIGSTOP, p);
- fake_signal_wake_up(p, task_is_stopped(p));
-}
-
static int has_mm(struct task_struct *p)
{
return (p->mm && !(p->flags & PF_BORROWED_MM));
@@ -121,7 +114,7 @@ static int freeze_task(struct task_struct *p, int with_mm_only)
if (freezing(p)) {
if (has_mm(p)) {
if (!signal_pending(p))
- fake_signal_wake_up(p, 0);
+ fake_signal_wake_up(p);
} else {
if (with_mm_only)
ret = 0;
@@ -135,7 +128,7 @@ static int freeze_task(struct task_struct *p, int with_mm_only)
} else {
if (has_mm(p)) {
set_freeze_flag(p);
- send_fake_signal(p);
+ fake_signal_wake_up(p);
} else {
if (with_mm_only) {
ret = 0;
@@ -182,15 +175,17 @@ static int try_to_freeze_tasks(int freeze_user_space)
if (frozen(p) || !freezeable(p))
continue;
- if (task_is_traced(p) && frozen(p->parent)) {
- cancel_freezing(p);
- continue;
- }
-
if (!freeze_task(p, freeze_user_space))
continue;
- if (!freezer_should_skip(p))
+ /*
+ * Now that we've done set_freeze_flag, don't
+ * perturb a task in TASK_STOPPED or TASK_TRACED.
+ * It is "frozen enough". If the task does wake
+ * up, it will immediately call try_to_freeze.
+ */
+ if (!task_is_stopped_or_traced(p) &&
+ !freezer_should_skip(p))
todo++;
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
diff --git a/kernel/signal.c b/kernel/signal.c
index 84917fe507f..6af1210092c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1623,7 +1623,6 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
/* Let the debugger run. */
__set_current_state(TASK_TRACED);
spin_unlock_irq(&current->sighand->siglock);
- try_to_freeze();
read_lock(&tasklist_lock);
if (!unlikely(killed) && may_ptrace_stop()) {
do_notify_parent_cldstop(current, CLD_TRAPPED);
@@ -1641,6 +1640,13 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
}
/*
+ * While in TASK_TRACED, we were considered "frozen enough".
+ * Now that we woke up, it's crucial if we're supposed to be
+ * frozen that we freeze now before running anything substantial.
+ */
+ try_to_freeze();
+
+ /*
* We are back. Now reacquire the siglock before touching
* last_siginfo, so that we are sure to have synchronized with
* any signal-sending on another CPU that wants to examine it.
@@ -1757,9 +1763,15 @@ int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
sigset_t *mask = &current->blocked;
int signr = 0;
+relock:
+ /*
+ * We'll jump back here after any time we were stopped in TASK_STOPPED.
+ * While in TASK_STOPPED, we were considered "frozen enough".
+ * Now that we woke up, it's crucial if we're supposed to be
+ * frozen that we freeze now before running anything substantial.
+ */
try_to_freeze();
-relock:
spin_lock_irq(&current->sighand->siglock);
for (;;) {
struct k_sigaction *ka;