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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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