Re: [PATCHv2 1/3] eventfd: allow atomic read and waitqueue remove

From: Avi Kivity
Date: Thu Jan 21 2010 - 12:57:33 EST

On 01/21/2010 07:56 PM, Avi Kivity wrote:
On 01/21/2010 07:45 PM, Michael S. Tsirkin wrote:

But you're in process context. An eventfd never blocks.
Yes it blocks if counter is 0. And we don't know
it's not 0 unless we read :) catch-22.

Ah yes, I forgot.

Well, you can poll it and then read it... this introduces a new race (if userspace does a read in parallel) but it's limited to kvm and buggy userspace.

Do not meddle in the internals of kernels, for they are subtle and quick to panic.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at