On Sun, 2009-05-24 at 09:29 -0500, James Bottomley wrote:
> The problem occurs when async_synchronize_full_domain() is called when
> the async_pending list is not empty. This will cause lowest_running()
> to return the cookie of the first entry on the async_pending list, which
> might be nothing at all to do with the domain being asked for and thus
> cause the domain synchronization to wait for an unrelated domain. This
> can cause a deadlock if domain synchronization is used from one domain
> to wait for another.
>
> Fix by running over the async_pending list to see if any pending items
> actually belong to our domain (and return their cookies if they do).
>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
OK, so that version locked up under testing ... this version doesn't ---
I think the phrase "MUST be called with the lock held!" was supposed to
be some sort of clue ...
James
---
diff --git a/kernel/async.c b/kernel/async.c
index 968ef94..13ed571 100644
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -92,19 +92,21 @@ extern int initcall_debug;
static async_cookie_t __lowest_in_progress(struct list_head *running)
{
struct async_entry *entry;
+ async_cookie_t ret = next_cookie; /* begin with "infinity" value */
+
if (!list_empty(running)) {
entry = list_first_entry(running,
struct async_entry, list);
- return entry->cookie;
+ ret = entry->cookie;
} else if (!list_empty(&async_pending)) {
- entry = list_first_entry(&async_pending,
- struct async_entry, list);
- return entry->cookie;
- } else {
- /* nothing in progress... next_cookie is "infinity" */
- return next_cookie;
+ list_for_each_entry(entry, &async_pending, list)
+ if (entry->running == running) {
+ ret = entry->cookie;
+ break;
+ }
}
+ return ret;
}
static async_cookie_t lowest_in_progress(struct list_head *running)
--
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