Messages in this thread | | | Date | Thu, 12 Apr 2012 16:09:12 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] eventfd: change int to __u64 in eventfd_signal() |
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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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