[whatwg] Accessing cookies from workers

Jonas Sicking jonas at sicking.cc
Thu Mar 5 17:55:23 PST 2009

On Thu, Mar 5, 2009 at 5:44 PM, Drew Wilson <atwilson at google.com> wrote:
> So an asynchronous cookie setting API would look like:
> setCookie(cookieStr, callback)
> ...where the callback is invoked once the cookie has been set?
> I guess I don't yet entirely understand the implementation details - it
> sounds like there are problems accessing any shared state between workers
> and window context?

The problem is with code like the following:

if (sharedState < 0) {
  sharedState = sharedState * -1;

You would expect sharedState to always be non-negative at the end of
such a program, right? Well, that might not be the case since script
running in parallel in the main window might have changed the value of
sharedState from -5 to 10 between the if-statement and the assignment,
resulting in sharedState being -10 at the end.

This is why workers use a shared-nothing message passing interface
between workers and windows. This is something that simply can't be
fixed in the implementation, but something that scripts would have to
deal with themselves. It's unlikely that web developers would do this
correctly since working with threads is *very hard* and something that
even seasoned developers often get wrong.

/ Jonas

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