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SubjectRe: [PATCH] powerpc: eeh_event: convert semaphore to completion
On Tue, Dec 11, 2018 at 8:52 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> For this use case, completions and semaphores are equivalent,
> but semaphores are an awkward interface that should generally
> be avoided, so use the completion instead.

IIRC Sam has been reworking the locking used inside of EEH so this is
probably going to clash with his changes. Converting to a completion
is probably a good idea, but we might want to do it as a part of his
series since it's going to collide with this anyway.

Sam, what do you think?

>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> arch/powerpc/kernel/eeh_event.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/kernel/eeh_event.c b/arch/powerpc/kernel/eeh_event.c
> index 61c9356bf9c9..227e57f980df 100644
> --- a/arch/powerpc/kernel/eeh_event.c
> +++ b/arch/powerpc/kernel/eeh_event.c
> @@ -35,7 +35,7 @@
> */
>
> static DEFINE_SPINLOCK(eeh_eventlist_lock);
> -static struct semaphore eeh_eventlist_sem;
> +static DECLARE_COMPLETION(eeh_eventlist_event);
> static LIST_HEAD(eeh_eventlist);
>
> /**
> @@ -55,7 +55,7 @@ static int eeh_event_handler(void * dummy)
> struct eeh_pe *pe;
>
> while (!kthread_should_stop()) {
> - if (down_interruptible(&eeh_eventlist_sem))
> + if (wait_for_completion_interruptible(&eeh_eventlist_event))
> break;
>
> /* Fetch EEH event from the queue */
> @@ -102,9 +102,6 @@ int eeh_event_init(void)
> struct task_struct *t;
> int ret = 0;
>
> - /* Initialize semaphore */
> - sema_init(&eeh_eventlist_sem, 0);
> -
> t = kthread_run(eeh_event_handler, NULL, "eehd");
> if (IS_ERR(t)) {
> ret = PTR_ERR(t);
> @@ -142,7 +139,7 @@ int eeh_send_failure_event(struct eeh_pe *pe)
> spin_unlock_irqrestore(&eeh_eventlist_lock, flags);
>
> /* For EEH deamon to knick in */
> - up(&eeh_eventlist_sem);
> + complete(&eeh_eventlist_event);
>
> return 0;
> }
> --
> 2.20.0
>

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