From: Tejun Heo Date: Fri, 12 Sep 2014 19:14:30 +0000 (+0900) Subject: workqueue: apply __WQ_ORDERED to create_singlethread_workqueue() X-Git-Tag: fixes-for-v3.18-merge-window~91^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e09c2c295468476a239d13324ce9042ec4de05eb;p=pandora-kernel.git workqueue: apply __WQ_ORDERED to create_singlethread_workqueue() create_singlethread_workqueue() is a compat interface for single threaded workqueue which maps to ordered workqueue w/ rescuer in the current implementation. create_singlethread_workqueue() currently implemented by invoking alloc_workqueue() w/ appropriate parameters. 8719dceae2f9 ("workqueue: reject adjusting max_active or applying attrs to ordered workqueues") introduced __WQ_ORDERED to protect ordered workqueues against dynamic attribute changes which can break ordering guarantees but forgot to apply it to create_singlethread_workqueue(). This in itself is okay as nobody currently uses dynamic attribute change on workqueues created with create_singlethread_workqueue(). However, 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues") broke singlethreaded guarantee for ordered workqueues through allocating a separate pool_workqueue on each NUMA node by default. A later change 8a2b75384444 ("workqueue: fix ordered workqueues in NUMA setups") fixed it by allocating only one global pool_workqueue if __WQ_ORDERED is set. Combined, the __WQ_ORDERED omission in create_singlethread_workqueue() became critical breaking its single threadedness and ordering guarantee. Let's make create_singlethread_workqueue() wrap alloc_ordered_workqueue() instead so that it inherits __WQ_ORDERED and can implicitly track future ordered_workqueue changes. v2: I missed that __WQ_ORDERED now protects against pwq splitting across NUMA nodes and incorrectly described the patch as a nice-to-have fix to protect against future dynamic attribute usages. Oleg pointed out that this is actually a critical breakage due to 8a2b75384444 ("workqueue: fix ordered workqueues in NUMA setups"). Signed-off-by: Tejun Heo Reported-by: Mike Anderson Cc: Oleg Nesterov Cc: Gustavo Luiz Duarte Cc: Tomas Henzl Cc: stable@vger.kernel.org Fixes: 4c16bd327c ("workqueue: implement NUMA affinity for unbound workqueues") --- Reading git-diff-tree failed