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SubjectRe: [PATCH] eventfd: change int to __u64 in eventfd_signal()
On Thu, 12 Apr 2012 18:01:20 +0800
handai.szj@gmail.com wrote:

> From: Sha Zhengju <handai.szj@taobao.com>
>
> From: Sha Zhengju <handai.szj@taobao.com>
>
> eventfd_ctx->count is an __u64 counter which is allowed to reach ULLONG_MAX.
> Now eventfd_write() add an __u64 value to "count", but kernel side
> eventfd_signal() only add an int value to it. So make them consistent here.
>
> ...
>
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -51,7 +51,7 @@ struct eventfd_ctx {
> *
> * -EINVAL : The value of @n is negative.
> */
> -int eventfd_signal(struct eventfd_ctx *ctx, int n)
> +__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
> {
> unsigned long flags;
>
> @@ -59,7 +59,7 @@ int eventfd_signal(struct eventfd_ctx *ctx, int n)
> return -EINVAL;
> spin_lock_irqsave(&ctx->wqh.lock, flags);
> if (ULLONG_MAX - ctx->count < n)
> - n = (int) (ULLONG_MAX - ctx->count);
> + n = ULLONG_MAX - ctx->count;
> ctx->count += n;
> if (waitqueue_active(&ctx->wqh))
> wake_up_locked_poll(&ctx->wqh, POLLIN);

Changing `n' to an unsigned type makes the "if (n < 0)" test a no-op.
Every in-kernel caller of eventfd_signal() passes n=1. All of them.
Perhaps we can just remove that argument and hard-wire the +1
assumption into eventfd_signal().



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