* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> $ git grep DECLARE_WAIT_QUEUE_HEAD_ONSTACK | wc -l
> 28
This debug facility looks sensible. A couple of minor suggestions:
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -39,6 +39,9 @@ struct wait_bit_queue {
> struct __wait_queue_head {
> spinlock_t lock;
> struct list_head task_list;
> +#ifdef CONFIG_DEBUG_WAITQUEUE
> + int onstack;
> +#endif
The structure will pack better in the debug-enabled case if 'onstack' is next to
'lock', as spinlock_t is 4 bytes on many architectures.
> -#define __WAIT_QUEUE_HEAD_INITIALIZER(name) { \
> +#ifdef CONFIG_DEBUG_WAITQUEUE
> +#define ___WAIT_QUEUE_ONSTACK(onstack) .onstack = (onstack),
> +#else
> +#define ___WAIT_QUEUE_ONSTACK(onstack)
> +#endif
Please help readers by showing the internal structure of the definition:
#ifdef CONFIG_DEBUG_WAITQUEUE
# define ___WAIT_QUEUE_ONSTACK(onstack) .onstack = (onstack),
#else
# define ___WAIT_QUEUE_ONSTACK(onstack)
#endif
> +static inline void prepare_debug(wait_queue_head_t *q, wait_queue_t *wait)
> +{
> +#ifdef CONFIG_DEBUG_WAITQUEUE
> + WARN_ON_ONCE(q->onstack && wait->func == autoremove_wake_function)
> +#endif
> +}
I'd name this debug_waitqueue_check() or such - as the 'prepare' is a bit
misleadig (we don't prepare debugging, we do the debug check here).
> +config DEBUG_WAITQUEUE
> + bool "Debug waitqueue"
> + depends on DEBUG_KERNEL
I'd name it DEBUG_SCHED_WAITQUEUE=y and I'd also make it depend on
CONFIG_DEBUG_SCHED.
LGTM otherwise!
Thanks,
Ingo
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