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Message-Id: <200702252017.22077.rjw@sisk.pl>
Date: Sun, 25 Feb 2007 20:17:20 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: "Aneesh Kumar" <aneesh.kumar@...il.com>
Cc: "Pavel Machek" <pavel@....cz>, LKML <linux-kernel@...r.kernel.org>,
paulmck@...ux.vnet.ibm.com, ego@...ibm.com, akpm@...l.org,
mingo@...e.hu, vatsa@...ibm.com, dipankar@...ibm.com,
venkatesh.pallipadi@...el.com, "Oleg Nesterov" <oleg@...sign.ru>
Subject: Re: [RFC][PATCH 4/7] Freezer: Fix vfork problem
On Sunday, 25 February 2007 16:40, Aneesh Kumar wrote:
> On 2/25/07, Aneesh Kumar <aneesh.kumar@...il.com> wrote:
> > On 2/25/07, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > On Sunday, 25 February 2007 15:33, Aneesh Kumar wrote:
> > > > On 2/25/07, Rafael J. Wysocki <rjw@...k.pl> wrote:
[--snip--]
>
> Thinking about this i guess we have a problem with the above approach
> i outlined. if we have one task that is waiting on the event and more
> than one that can generate the event then the above logic would not
> work. Also with cases other than vfork; logic of tracking the waiting
> task gets complex. I guess what we have right now is better.
I assume by "righ now" you mean the latest version of my patch. ;-)
Still, having pondered the Pavel's suggestion for a while I think it's doable
without the addtitional process flag. Patch below.
Greetings,
Rafael
include/linux/completion.h | 13 ++++++++++++-
kernel/fork.c | 2 +-
kernel/power/process.c | 20 ++++++--------------
kernel/sched.c | 8 ++++++--
4 files changed, 25 insertions(+), 18 deletions(-)
Index: linux-2.6.20-mm2/include/linux/completion.h
===================================================================
--- linux-2.6.20-mm2.orig/include/linux/completion.h 2007-02-25 14:02:54.000000000 +0100
+++ linux-2.6.20-mm2/include/linux/completion.h 2007-02-25 20:20:35.000000000 +0100
@@ -42,7 +42,18 @@ static inline void init_completion(struc
init_waitqueue_head(&x->wait);
}
-extern void FASTCALL(wait_for_completion(struct completion *));
+extern void FASTCALL(__wait_for_completion(struct completion *, int));
+
+static inline void wait_for_completion(struct completion *x)
+{
+ __wait_for_completion(x, 0);
+}
+
+static inline void wait_for_completion_freezable(struct completion *x)
+{
+ __wait_for_completion(x, 1);
+}
+
extern int FASTCALL(wait_for_completion_interruptible(struct completion *x));
extern unsigned long FASTCALL(wait_for_completion_timeout(struct completion *x,
unsigned long timeout));
Index: linux-2.6.20-mm2/kernel/sched.c
===================================================================
--- linux-2.6.20-mm2.orig/kernel/sched.c 2007-02-25 14:02:54.000000000 +0100
+++ linux-2.6.20-mm2/kernel/sched.c 2007-02-25 20:20:35.000000000 +0100
@@ -3803,7 +3803,8 @@ void fastcall complete_all(struct comple
}
EXPORT_SYMBOL(complete_all);
-void fastcall __sched wait_for_completion(struct completion *x)
+void fastcall __sched
+__wait_for_completion(struct completion *x, int freezable)
{
might_sleep();
@@ -3817,6 +3818,9 @@ void fastcall __sched wait_for_completio
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
schedule();
+ if (freezable)
+ try_to_freeze();
+
spin_lock_irq(&x->wait.lock);
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
@@ -3824,7 +3828,7 @@ void fastcall __sched wait_for_completio
x->done--;
spin_unlock_irq(&x->wait.lock);
}
-EXPORT_SYMBOL(wait_for_completion);
+EXPORT_SYMBOL(__wait_for_completion);
unsigned long fastcall __sched
wait_for_completion_timeout(struct completion *x, unsigned long timeout)
Index: linux-2.6.20-mm2/kernel/fork.c
===================================================================
--- linux-2.6.20-mm2.orig/kernel/fork.c 2007-02-25 20:17:25.000000000 +0100
+++ linux-2.6.20-mm2/kernel/fork.c 2007-02-25 20:20:35.000000000 +0100
@@ -1393,7 +1393,7 @@ long do_fork(unsigned long clone_flags,
tracehook_report_clone_complete(clone_flags, nr, p);
if (clone_flags & CLONE_VFORK) {
- wait_for_completion(&vfork);
+ wait_for_completion_freezable(&vfork);
tracehook_report_vfork_done(p, nr);
}
} else {
Index: linux-2.6.20-mm2/kernel/power/process.c
===================================================================
--- linux-2.6.20-mm2.orig/kernel/power/process.c 2007-02-25 20:17:25.000000000 +0100
+++ linux-2.6.20-mm2/kernel/power/process.c 2007-02-25 20:20:35.000000000 +0100
@@ -48,6 +48,9 @@ void refrigerator(void)
task_unlock(current);
return;
}
+ if (current->vfork_done)
+ wake_up_process(current->parent);
+
save = current->state;
pr_debug("%s entered refrigerator\n", current->comm);
@@ -127,21 +130,10 @@ static unsigned int try_to_freeze_tasks(
cancel_freezing(p);
continue;
}
- if (is_user_space(p)) {
- if (!freeze_user_space)
- continue;
-
- /* Freeze the task unless there is a vfork
- * completion pending
- */
- if (!p->vfork_done)
- freeze_process(p);
- } else {
- if (freeze_user_space)
- continue;
+ if (is_user_space(p) == !freeze_user_space)
+ continue;
- freeze_process(p);
- }
+ freeze_process(p);
todo++;
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
-
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