Messages in this thread Patches in this message | | | Date | Sun, 11 May 2008 14:50:49 +0200 | From | Ingo Molnar <> | Subject | Re: [git pull] scheduler fixes |
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* Matthew Wilcox <matthew@wil.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@elte.hu> Date: Sun May 11 09:51:07 CEST 2008
Signed-off-by: Ingo Molnar <mingo@elte.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@elte.hu> Date: Thu May 08 11:53:48 CEST 2008 Signed-off-by: Ingo Molnar <mingo@elte.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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