This reverts commit 92266d6ef60c2381c980c6cdcb2a5c1667b36b49, which was simply wrong: In the case where domain is NULL, we now use the wrong offsetof() in the list_first_entry macro, so we don't actually fetch the ->cookie value, but rather the eight bytes located sizeof(struct list_head) further into the struct async_entry.
On 64 bit, that's the data member, while on 32 bit, that's a u64 built from func and data in some order.
I think the bug happens to be harmless in practice: It obviously only affects callers which pass a NULL domain, and AFAICT the only such caller is
async_synchronize_full() -> async_synchronize_full_domain(NULL) -> async_synchronize_cookie_domain(ASYNC_COOKIE_MAX, NULL)
and the ASYNC_COOKIE_MAX means that in practice we end up waiting for the async_global_pending list to be empty - but it would break if somebody happened to pass (void*)-1 as the data element to async_schedule, and of course also if somebody ever does a async_synchronize_cookie_domain(, NULL) with a "finite" cookie value.
Cc: stable@vger.kernel.org # 3.10+ Fixes: 92266d6ef60c "async: simplify lowest_in_progress()" Acked-by: Tejun Heo tj@kernel.org Signed-off-by: Rasmus Villemoes linux@rasmusvillemoes.dk --- Resending with Cc akpm, added ack from Tejun.
Maybe the "harmless in practice" means this isn't -stable material. But I'm not completely confident my quick git grep'ing is enough, and there might be affected code in one of the earlier kernels that has since been removed, so I'll leave the decision to the stable guys.
kernel/async.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/kernel/async.c b/kernel/async.c index 2cbd3dd5940d..a893d6170944 100644 --- a/kernel/async.c +++ b/kernel/async.c @@ -84,20 +84,24 @@ static atomic_t entry_count;
static async_cookie_t lowest_in_progress(struct async_domain *domain) { - struct list_head *pending; + struct async_entry *first = NULL; async_cookie_t ret = ASYNC_COOKIE_MAX; unsigned long flags;
spin_lock_irqsave(&async_lock, flags);
- if (domain) - pending = &domain->pending; - else - pending = &async_global_pending; + if (domain) { + if (!list_empty(&domain->pending)) + first = list_first_entry(&domain->pending, + struct async_entry, domain_list); + } else { + if (!list_empty(&async_global_pending)) + first = list_first_entry(&async_global_pending, + struct async_entry, global_list); + }
- if (!list_empty(pending)) - ret = list_first_entry(pending, struct async_entry, - domain_list)->cookie; + if (first) + ret = first->cookie;
spin_unlock_irqrestore(&async_lock, flags); return ret;