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Message-ID: <20080511125049.GA22513@elte.hu>
Date: Sun, 11 May 2008 14:50:49 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Matthew Wilcox <matthew@....cx>
Cc: Sven Wegener <sven.wegener@...aler.net>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
Andi Kleen <andi@...stfloor.org>,
LKML <linux-kernel@...r.kernel.org>,
Alexander Viro <viro@....linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [git pull] scheduler fixes
* Matthew Wilcox <matthew@....cx> wrote:
> So I deem my fix "proven by thought experiment". I haven't tried
> booting it or anything.
i actually have two fixes, made earlier today. The 'fix3' one has been
confirmed by Sven to fix the regression - but i think we need the 'fix
#2' one below as well to make it complete.
Ingo
-------------------->
Subject: semaphore: fix3
From: Ingo Molnar <mingo@...e.hu>
Date: Sun May 11 09:51:07 CEST 2008
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/semaphore.c | 7 +++++++
1 file changed, 7 insertions(+)
Index: linux/kernel/semaphore.c
===================================================================
--- linux.orig/kernel/semaphore.c
+++ linux/kernel/semaphore.c
@@ -258,5 +258,12 @@ static noinline void __sched __up(struct
{
struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list,
struct semaphore_waiter, list);
+
+ /*
+ * Rotate sleepers - to make sure all of them get woken in case
+ * of parallel up()s:
+ */
+ list_move_tail(&waiter->list, &sem->wait_list);
+
wake_up_process(waiter->task);
}
---------------->
Subject: semaphore: fix #2
From: Ingo Molnar <mingo@...e.hu>
Date: Thu May 08 11:53:48 CEST 2008
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/semaphore.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
Index: linux/kernel/semaphore.c
===================================================================
--- linux.orig/kernel/semaphore.c
+++ linux/kernel/semaphore.c
@@ -194,6 +194,13 @@ struct semaphore_waiter {
struct task_struct *task;
};
+static noinline void __sched __up(struct semaphore *sem)
+{
+ struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list,
+ struct semaphore_waiter, list);
+ wake_up_process(waiter->task);
+}
+
/*
* Because this function is inlined, the 'state' parameter will be
* constant, and thus optimised away by the compiler. Likewise the
@@ -231,6 +238,9 @@ static inline int __sched __down_common(
}
list_del(&waiter.list);
+ if (unlikely(!list_empty(&sem->wait_list)) && sem->count)
+ __up(sem);
+
return ret;
}
@@ -254,9 +264,3 @@ static noinline int __sched __down_timeo
return __down_common(sem, TASK_UNINTERRUPTIBLE, jiffies);
}
-static noinline void __sched __up(struct semaphore *sem)
-{
- struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list,
- struct semaphore_waiter, list);
- wake_up_process(waiter->task);
-}
--
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