Update cache-control.mdx (cloudflare#23628)

* Update cache-control.mdx

Clarifying current stale-while-revalidate behaviour

* Update src/content/docs/cache/concepts/cache-control.mdx

* Update src/content/docs/cache/concepts/cache-control.mdx

---------

Co-authored-by: angelampcosta <[email protected]>

Author: 2 people

src/content/docs/cache/concepts/cache-control.mdx

@@ -77,6 +77,15 @@ Revalidation determines how the cache should behave when a resource expires, and
 * `must-revalidate` — Indicates that once the resource is stale, a cache (client or proxy) must not use the response to satisfy subsequent requests without successful validation on the origin server.
 * `proxy-revalidate` — Has the same meaning as the `must-revalidate` response directive except that it does not apply to private client caches.
 * `stale-while-revalidate=<seconds>` — When present in an HTTP response, indicates caches may serve the response in which it appears after it becomes stale, up to the indicated number of seconds since the resource expired. If [Always Online](/cache/how-to/always-online/) is enabled, then the `stale-while-revalidate` and `stale-if-error` directives are ignored. This directive is not supported when using the Cache API methods `cache.match` or `cache.put`. For more information, refer to the [Worker's documentation for Cache API](/workers/runtime-apis/cache/#methods).
+
+:::note
+Currently, `stale-while-revalidate` blocks on the first request that hits a stale cache item in the cache location, when the origin returns a response it will be served to this client with a MISS or REVALIDATED status.
+
+Any other requests that arrive while this is happening in the same cache location for the same cached item will be served stale with the UPDATING status.
+
+For more details on this, refer to example 1 of our [Revalidation and request collapsing](/cache/concepts/revalidation/#example-1) guide.
+:::
+
 * `stale-if-error=<seconds>` — Indicates that when an error is encountered, a cached stale response may be used to satisfy the request, regardless of other freshness information. To avoid this behavior, include `stale-if-error=0` directive with the object returned from the origin. This directive is not supported when using the Cache API methods `cache.match` or `cache.put`. For more information, refer to the [Worker's documentation for Cache API](/workers/runtime-apis/cache/#methods).
 
 The `stale-if-error` directive is ignored if [Always Online](/cache/how-to/always-online/) is enabled or if an explicit in-protocol directive is passed. Examples of explicit in-protocol directives include a `no-store` or `no-cache cache` directive, a `must-revalidate` cache-response-directive, or an applicable `s-maxage` or `proxy-revalidate` cache-response-directive.